Blood Studies: Hematology and Coagulation
OVERVIEW OF BASIC BLOOD, HEMATOLOGY, AND COAGULATION TESTS
Composition of Blood
The average person circulates about 5 L of blood (1/13 of total body weight), of which 3 L is plasma and 2 L is cells. Plasma fluid derives from the intestines and lymphatic systems and provides a vehicle for cell movement. The cells are produced primarily by the bone marrow and account for blood “solids.” Blood cells are classified as white cells (leukocytes), red cells (erythrocytes), and platelets (thrombocytes). White cells are further categorized as granulocytes (neutrophils, basophils, and eosinophils), lymphocytes, and monocytes.
Before birth, hematopoiesis occurs in the liver. In midfetal life, the spleen and lymph nodes play a minor role in cell production. Shortly after birth, hematopoiesis in the liver ceases and the bone marrow is the only site of production of erythrocytes, granulocytes, and platelets. B lymphocytes are produced in the marrow and in the secondary lymphoid organs; T lymphocytes are produced in the thymus.
Blood Tests
Tests in this chapter are basic screening tests that address disorders of hemoglobin (Hb) and hematopoiesis, synthesis, and function. Blood and bone marrow examinations constitute the major means of determining certain blood disorders (anemia, leukemia and porphyria disorders, abnormal bleeding
and clotting); inflammation; infection; and inherited disorders of red blood cells (RBCs), white blood cells (WBCs), and platelets. Specimens are obtained through capillary skin punctures (finger, toe, heel), dried blood samples, arterial or venous sampling, or bone marrow aspiration. Specimens may be tested by automated or manual hematology instrumentation and evaluation.
and clotting); inflammation; infection; and inherited disorders of red blood cells (RBCs), white blood cells (WBCs), and platelets. Specimens are obtained through capillary skin punctures (finger, toe, heel), dried blood samples, arterial or venous sampling, or bone marrow aspiration. Specimens may be tested by automated or manual hematology instrumentation and evaluation.
BLOOD SPECIMEN COLLECTION PROCEDURES
Proper specimen collection presumes correct technique and accurate timing when necessary. Although blood tests are common procedures for many patients, fear of needles or sight of blood may cause fear or anxiety. Always assess the patient for these factors and provide patient education, reassurance, and support. Most hematology tests use liquid ethylenediaminetetraacetic acid (EDTA) as an anticoagulant. Tubes with anticoagulants should be gently but completely inverted end-over-end 7 to 10 times after collection. This action ensures complete mixing of anticoagulants with blood to prevent clot formation. Even slightly clotted blood invalidates the test, and the sample must be redrawn.
For plasma coagulation studies, such as prothrombin time (PT) and partial thromboplastin time (PTT), the tube must be allowed to fill to its capacity or an improper blood-to-anticoagulant ratio will invalidate coagulator results. Invert the tube end-over-end 7 to 10 times to prevent clotting.
• Capillary Puncture (Skin Puncture)
Capillary blood is preferred for a peripheral blood smear and can also be used for other hematology studies. Adult capillary blood samples require a skin puncture, usually of the fingertip or earlobe. For children over 1 year of age, the tip of the finger is often used. Under 1 year of age, the best sample is obtained from the great toe or side of the heel.
Procedure
Capillary Blood
Observe standard precautions (see Appendix A). Check for latex allergy. If allergy is present, do not use latex-containing products.
Obtain capillary blood from fingertips or earlobes (adults) or from the great toe or heel (newborns and infants younger than 1 year). Avoid using the lateral aspect of the heel where the plantar artery is located.
Disinfect puncture site, let it dry, and puncture skin with sterile disposable lancet, perpendicular to the lines of the patient’s fingers, no deeper than 2 mm. If chlorhexidine is used, allow to dry thoroughly.
Wipe away the initial drop of blood. Collect subsequent drops in a microtube or prepare a smear directly from a drop of blood.
After collection, apply a small amount of pressure briefly to the puncture site to prevent painful extravasation of blood into the subcutaneous tissues.
PROCEDURAL ALERT
Do not squeeze the site to obtain blood because this alters blood composition and invalidates test values.
Warming the extremity or placing it in a dependent position may facilitate specimen collection.
Dried Blood Spot
In this method, a lancet is used, and the resulting droplets of blood are collected by blotting them with filter paper directly.
Check the stability of equipment and integrity of supplies when doing a finger stick. If provided, check the humidity indicator patch on the filter paper card. If the humidity circle is pink, do not use the filter paper card. The humidity indicator must be blue to ensure specimen integrity.
After wiping the first drop of blood on the gauze pad, fill and saturate each of the circles in numerical order by blotting the blood droplet with the filter paper. Do not touch the patient’s skin to the filter paper; only the blood droplet should come in contact with the filter paper.
If an adult has a cold hand, run warm water over it for approximately 3 minutes. The best flow occurs when the arm is held downward, with the hand below heart level, making effective use of gravity. If there is a problem with proper blood flow, milk the finger with gentle pressure to stimulate blood flow or attempt a second finger stick; do not attempt more than two times.
When the blood circles penetrate through to the other side of the filter paper, the circles are fully saturated.
Interventions
Pretest Patient Care
Instruct the patient about purpose and procedure of test.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Apply small dressing or adhesive bandage to site.
Evaluate puncture site for bleeding or oozing.
Apply compression or pressure to the site if it continues to bleed.
Evaluate patient’s medication history for anticoagulation, nonsteroidal anti-inflammatory drugs (NSAIDs), or acetylsalicylic acid (ASA)-type drug ingestion.
Review test results; report and record findings. Modify the nursing care plan as needed.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
• Venipuncture
Venipuncture allows procurement of larger quantities of blood for testing. Care must be taken to avoid sample hemolysis or hemoconcentration and to prevent hematoma, vein damage, infection, and discomfort. Usually, the antecubital veins are the veins of choice because of ease of access. Blood values remain constant no matter which venipuncture site is selected, so long as it is venous and not arterial blood. Sometimes, the wrist area, forearm, or dorsum of the hand or foot must be used. Blood values remain consistent for all of these venipuncture sites.
Observe standard precautions (see Appendix A). If latex allergy is known or suspected, use latexfree supplies and equipment.
Assess the patient for fear or anxiety related to the procedure. Provide education, reassurance, and a supportive presence.
Position and tighten a tourniquet on the upper arm to produce venous distention (congestion). For elderly persons, a tourniquet is not always recommended because of possible rupture of capillaries. Large, distended, and highly visible veins increase the risk for hematoma.
Ask the patient to close the fist in the designated arm. Do not ask patient to pump the fist because this may increase plasma potassium levels by as much as 1 to 2 mEq/L (mmol/L). Select an accessible vein.
Cleanse the puncture site, working in a circular motion from the center outward, and dry it properly with sterile gauze. Chlorhexidine must dry thoroughly.
To anchor the vein, draw the skin taut over the vein and press the thumb below the puncture site. Hold the distal end of the vein during the puncture to decrease the possibility of rolling veins.
Puncture the vein according to accepted technique. Usually, for an adult, anything smaller than a 21-gauge needle might make blood withdrawal more difficult. A Vacutainer system syringe or butterfly system may be used.
Once the vein has been entered by the collecting needle, blood will fill the attached vacuum tubes automatically because of negative pressure within the collection tube.
Remove the tourniquet before removing the needle from the puncture site or bruising will occur.
Remove needle. Apply pressure and sterile dressing strip to puncture site.
The preservative or anticoagulant added to the collection tube depends on the test ordered. In general, most hematology tests use EDTA anticoagulant. Even slightly clotted blood invalidates the test, and the sample must be redrawn.
Take action to prevent these venipuncture errors:
Pretest errors
Improper patient identification
Failure to check patient compliance with dietary restrictions
Failure to calm patient before blood collection
Use of wrong equipment and supplies
Inappropriate method of blood collection
Procedure errors
Failure to dry site completely after cleansing with alcohol or chlorhexidine
Inserting needle with bevel side down
Using too small a needle, causing hemolysis of specimen
Venipuncture in unacceptable area (e.g., above an intravenous [IV] line)
Prolonged tourniquet application
Wrong order of tube draw
Failure to mix blood immediately that is collected in additive-containing tubes
Pulling back on syringe plunger too forcefully
Failure to release tourniquet before needle withdrawal
Posttest errors
Failure to apply pressure immediately to venipuncture site
Vigorous shaking of anticoagulated blood specimens
Forcing blood through a syringe needle into tube
Mislabeling of tubes
Failure to label specimens with infectious disease precautions as required
Failure to put date, time, and initials on requisition
Slow or delayed transport of specimens to the laboratory
NOTE
A blood pressure cuff inflated to a point between systolic and diastolic pressure values can be used in place of a tourniquet.
NOTE
The Vacutainer system consists of vacuum tubes (Vacutainer tubes), a tube holder, and a disposable multisample collecting needle (Fig. 2.1).
 FIGURE 2.1. Evacuated tubes. Vacutainer Plus Plastic brand evacuated tubes. (Becton Dickinson, Franklin Lakes, NJ.) |
Interventions
Pretest Patient Care
Instruct patient regarding sampling procedure. Assess for circulation or bleeding problems and allergy to latex. Verify with the patient any fasting requirements. Diagnostic blood tests may require certain dietary restrictions of fasting for 8 to 12 hours before test. Drugs taken by the patient should be documented because they may affect results.
Reassure patient that only mild discomfort may be felt when the needle is inserted.
Place the arm in a fully extended position with palmar surface facing upward (for antecubital access).
If withdrawal of the sample is difficult, warm the extremity with warm towels or blankets. Allow the extremity to remain in a dependent position for several minutes before venipuncture. For young children, warming the draw site should be routine to distend small veins.
Be alert to provide assistance should the patient become lightheaded or faint.
Prescribed local anesthetic creams may be applied to the area before venipuncture; wait 60 seconds for light-skinned persons and 120 seconds for dark-skinned persons after application of the cream before performing the procedure.
Posttest Patient Care
If oozing or bleeding from the puncture site continues for more than a few minutes, elevate the area and apply a pressure dressing. Observe the patient closely. Check for anticoagulant or ASAtype ingestion. If venous bleeding is excessive and persists for longer than 10 minutes, notify the healthcare provider.
Be aware that the patient occasionally becomes dizzy, faint, or nauseated during the venipuncture. The phlebotomist must be constantly aware of the patient’s condition. If a patient feels faint, immediately remove the tourniquet and terminate the procedure. Place the patient in a supine position if possible. If the patient is sitting, lower the head between the legs and instruct the patient to breathe deeply. A cool, wet towel may be applied to the forehead and back of the neck, and, if necessary, ammonia inhalant may be applied briefly. Watch for signs of shock, such as increased heart rate and decreased blood pressure. If the patient becomes unconscious, notify the healthcare provider immediately.
Prevent hematomas by using proper technique (do not allow the needle to pass through the vein), releasing the tourniquet before the needle is withdrawn, applying sufficient pressure over the puncture site, and maintaining an extended extremity until bleeding stops. If a hematoma develops, apply a warm compress.
Assess the puncture site for signs and symptoms of infection, subcutaneous redness, pain, swelling, and tenderness.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
CLINICAL ALERT
In patients with leukemia, agranulocytosis, or lowered resistance, finger stick and earlobe punctures are more likely to cause infection and bleeding than venipunctures. Should a capillary sample be necessary, the cleansing agent should remain in contact with the skin for at least 5-10 min. Chlorhexidine is a topical antimicrobial. It should be allowed to dry. It may then be wiped off with alcohol and the site dried with sterile gauze before puncture.
Do not draw blood from the same extremity being used for IV medications, fluids, or transfusions. If no other site is available, make sure the venipuncture site is below the IV site. Avoid areas that are edematous, are paralyzed, are on the same side as a mastectomy, or have infections or skin conditions present. Venipuncture may cause infection or circulatory impairment or impaired healing.
Prolonged tourniquet application causes stasis and hemoconcentration and will alter test results. If a vein cannot be found within a minute, release the tourniquet temporarily to avoid tissue necrosis.
Strenuous activity immediately before a blood sample draw can alter results because body fluids shift from the vascular bed to the tissue spaces and produce circulatory blood hemoconcentration. It may take 20-30 min of rest and reduced stress to reestablish fluid equilibrium.
Assess for interfering factors, including cellulitis, phlebitis, venous obstruction, lymphangitis, or arteriovenous fistulas or shunts.
To avoid spurious test results due to infusion of solutions, do not draw above an IV catheter. Choose a site distal to the IV line site.
After two unsuccessful attempts, another trained member of the healthcare team should be called.
Blood samples may be drawn off central lines. The lines must be flushed with saline before the blood draw.
• Arterial Puncture
Arterial blood samples are necessary for arterial blood gas (ABG) determinations or when it is not possible to obtain a venous blood sample. Arterial sticks are usually performed by a physician or a specially trained nurse or technician because of the potential risks inherent in this procedure. Samples are normally collected directly from the radial, brachial, or femoral arteries. If the patient has an arterial line in place (most frequently in the radial artery), samples can be drawn from the line. Be sure to record the amounts of blood withdrawn in order to track and total the amounts that are removed when frequent samples are required.
ABG determinations are used to assess the status of oxygenation and ventilation, to evaluate the acid-base status by measuring the respiratory and nonrespiratory components, and to monitor effectiveness of therapy. ABGs are also used to monitor critically ill patients, to establish baseline laboratory values, to detect and treat electrolyte imbalances, to titrate appropriate oxygen therapy, to qualify a patient for home oxygen use, and to assess the patient’s status in conjunction with pulmonary function testing.
Arterial puncture sites must satisfy the following requirements:
Sites must have available collateral blood flow.
Sites must be easily accessible.
Sites must be relatively nonsensitive as periarterial tissues.
For patients requiring frequent arterial monitoring, an indwelling arterial catheter (line) may be inserted. Follow agency protocols for obtaining arterial line blood samples. The procedure varies for neonate, pediatric, and adult patients (see Arterial Blood Gas Tests in Chapter 14).
Interventions
Pretest Patient Care
Assess patient for the following contraindications to an arterial stick or indwelling arterial line in a particular area:
Absence of a palpable radial artery pulse
Positive Allen’s test result, which shows only one artery supplying blood to the hand
Negative modified Allen’s test result, which indicates obstruction in the ulnar artery (i.e., compromised collateral circulation)
Cellulitis or infection at the potential site
Presence of arteriovenous fistula or shunt
Severe thrombocytopenia (platelet count 20,000/mm3)
Prolonged PT or PTT (>1.5 times the control is a relative contraindication)
A Doppler probe or finger pulse transducer may be used to assess circulation and perfusion in dark-skinned or uncooperative patients.
Before drawing an arterial blood sample, record the patient’s most recent Hb concentration, mode and flow rate of oxygen, and temperature. If the patient has recently undergone suction or been placed on a ventilator or if delivered oxygen concentrations have been changed, wait at least 15 minutes before drawing the sample. This waiting period allows circulating blood levels to return to baseline levels. Hyperthermia and hypothermia also influence oxygen release from Hb at the tissue level.
Intratest Patient Care
Observe standard precautions and follow agency protocols for the procedure.
Place the patient in a sitting or supine position.
Perform a modified Allen’s test by encircling the wrist area and using pressure to obliterate the radial and ulnar pulses. Watch for the hand to blanch and then release pressure only over the ulnar artery. If the result is positive, flushing of the hand is immediately noticed, indicating circulation to the hand is adequate. The radial artery can then be used for arterial puncture. If collateral circulation from the ulnar artery is inadequate (i.e., negative test result) and flushing of the hand is absent or slow, then another site must be chosen. An abnormal Allen’s test result may be caused by a thrombus, an arterial spasm, or a systemic problem such as shock or poor cardiac output.
Elevate the wrist area by placing a small pillow or rolled towel under the dorsal wrist area. With the patient’s palm facing upward, ask the patient to extend the fingers downward, which flexes the wrist and positions the radial artery closer to the surface.
Palpate for the artery and maneuver the patient’s hand back and forth until a satisfactory pulse is felt.
Swab the area liberally with an antiseptic agent such as ChloraPrep.
OPTIONAL: Inject the area with a small amount (<0.25 mL) of 1% plain Xylocaine (Lidocaine), if necessary, to anesthetize site. Assess for allergy first. This allows for a second attempt without undue pain.
Prepare a 20- or 21-gauge needle on a preheparinized, self-filling syringe; puncture the artery; and collect a 3- to 5-mL sample. The arterial pressure pushes the plunger out as the syringe fills with blood. (Venous blood does not have enough pressure to fill the syringe without drawing back on the plunger.) Air bubbles in the blood sample must be expelled as quickly as possible because residual air alters ABG values. The syringe should then be capped and gently rotated to mix heparin with the blood.
When the draw is completed, withdraw the needle, and place a 4- × 4-inch absorbent bandage over the puncture site. Do not recap needles; if necessary, use the one-handed mechanical, recapping, or scoop technique, or commercially available needles (e.g., BD SafetyGlide [BD, Franklin Lakes, NJ] or Sims Portex Pro-Vent [Smiths Medical, Keene, NH]). Maintain firm finger pressure over the puncture site for a minimum of 5 minutes or until there is no active bleeding evident. After the bleeding stops, apply a firm pressure dressing but do not encircle the entire limb, which can restrict circulation. Leave this dressing in place for at least 24 hours. Instruct the patient to report any signs of bleeding from the site promptly and apply finger pressure if necessary.
Label the specimen with the patient’s name, date and time of collection, and test(s) ordered. Indicate the type and flow rate of O2 therapy or if the patient was on room air. Place the sample in an ice slurry and transport to the laboratory in a biohazard bag. Do not use blood for ABGs if the sample is more than 1 hour old.
In clinical settings such as the perioperative or intensive care environment, ABG studies usually include pH, PCO2, SO2, total CO2 content (TCO2), O2 content, PO2, base excess or deficit, HCO3, Hb, hematocrit (Hct), and levels of chloride, sodium, and potassium.
NOTE
Do not use Xylocaine that contains epinephrine; it causes blood vessel constriction and makes the arterial puncture difficult.
NOTE
Putting the sample in an ice slurry prevents alterations in gas tensions because metabolic processes within the sample otherwise continue after blood is drawn.
CLINICAL ALERTMetabolizing blood cells can quickly alter blood gas values (primarily PaO2) at normal body temperature (37°C). This occurs much slower at 0°C (i.e., temperature of ice water). An iced sample should remain stable for at least 1 hour. Any sample not placed in ice should be tested within minutes after it is drawn or else discarded. The main effect of cellular metabolism decreases PO2. Several studies have shown a remarkable fall in PaO2 if the blood contains >100,000 WBCs/mm3 (i.e., leukocyte larceny), even when the sample is on ice. A WBC count of this magnitude (usually in leukemia) should mandate special handling, such as testing the sample immediately. Alternatively, check the patient’s oxygen saturation by pulse oximetry, which is not affected by extreme leukocytosis.
CLINICAL ALERTSome patients may experience light-headedness, nausea, or vasovagal syncope during the arterial puncture. Treat according to established protocols.
Posttest Patient Care
Posttest assessment of the puncture site and extremity includes color, movement, sensation, degree of warmth, capillary refill time, and quality of the pulse.
The arterial puncture site must have a pressure dressing applied and should be frequently assessed for bleeding for several hours. Instruct the patient to report any bleeding from the site and to apply direct pressure to the site if bleeding occurs.
Frequently monitor the puncture site and dressing for arterial bleeding for several hours. Instruct the patient not to use the extremity for any vigorous activity for at least 24 hours.
Monitor the patient’s vital signs and mental function to determine adequacy of tissue oxygenation and perfusion.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
• Bone Marrow Aspiration
Bone marrow is located within cancellous bone and long-bone cavities. It consists of a pattern of vessels and nerves, differentiated and undifferentiated hematopoietic cells, reticuloendothelial cells, and fatty tissue. All of these are encased by endosteum, the membrane lining the bone marrow cavity. After proliferation and maturation have occurred in the marrow, blood cells gain entrance to the blood through or between the endothelial cells of the sinus wall.
A bone marrow specimen is obtained through aspiration or biopsy or needle biopsy aspiration. A bone marrow examination is important in the evaluation of a number of hematologic disorders and infectious diseases. The presence or suspicion of a blood disorder is not always an indication for bone marrow studies. A decision to use this procedure is made on an individual basis.
Sometimes, the bone marrow aspirate does not contain hematopoietic cells. This is known as a dry tap, which occurs when hematopoietic activity is so sparse that there are no cells to be withdrawn or when the marrow contains so many tightly packed cells that they cannot be suctioned out of the marrow. In such cases, a bone marrow biopsy would be advantageous. Before the bone marrow procedure is started, a peripheral blood smear should be obtained from the patient and a differential leukocyte count done.
Procedure
Assess the patient for fear or anxiety related to the procedure. Provide education, reassurance, and a supportive presence.
Follow standard precautions. Check for latex allergy; if allergy is present, do not use latexcontaining products. Position the patient on the back or side according to site selected. The posterior iliac crest is the preferred site in all patients older than 12 to 18 months. Alternate sites include the anterior iliac crest, sternum, spinous vertebral processes T10 through L4, ribs, and tibia in children. The sternum is not generally used in children because the bone cavity is too shallow, the risk for mediastinal and cardiac perforation is too great, and the child may be uncooperative.
Clip hair if necessary and cleanse and drape the site as for any minor surgical procedure.
Inject a local anesthetic (procaine or lidocaine). This may cause a burning sensation. At this time, a skin incision of 3 mm is often made.
The healthcare provider introduces a short, rigid, sharp-pointed needle with stylet through the periosteum into the marrow cavity.
Pass the needle-stylet combination through the incision, subcutaneous tissue, and bone cortex. The stylet is removed, and 1 to 3 mL of marrow fluid is aspirated. Alert the patient that when the stylet needle enters the marrow, he or she may experience a feeling of pressure. The patient may also feel moderate discomfort as aspiration is done, especially in the iliac crest. Use a Jamshidi needle for biopsy, although you can also use the Westerman-Jensen modification of the Vim-Silverman needle.
Remove the stylet and advance the biopsy needle with a twisting motion toward the anterosuperior iliac spine.
Rotate or “rock” the needle in several directions several times after adequate penetration of the base (3 cm) has been achieved. This frees up the specimen. Slowly withdraw the needle once this is done.
Push the biopsy specimen out backward from the needle. Use the specimen to make touch preparations or immediately place in fixative. Make slide smears at the bedside.
Apply pressure to the puncture site until bleeding ceases. Apply a sterile dressing to the site.
Label the specimen with the patient’s name, date and time of collection, and test(s) ordered.
TABLE 2.1 Normal Values for Bone Marrowa | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Clinical Implications
A specific and diagnostic bone marrow picture provides clues to many diseases. The presence, absence, and ratio of cells are characteristic of the suspected disease.
Bone marrow examination may reveal the following abnormal cell patterns:
Multiple myeloma, plasma cell myeloma, macroglobulinemia
Chronic or acute leukemias
Anemia, including megaloblastic, macrocytic, and normocytic anemias
Toxic states that produce bone marrow depression or destruction
Neoplastic diseases in which the marrow is invaded by tumor cells (metastatic carcinoma, myeloproliferative and lymphoproliferative diseases)
Agranulocytosis, which occurs when bone marrow activity is severely depressed, usually is a result of radiation therapy or chemotherapeutic drugs.
Platelet dysfunction
Some types of infectious diseases, especially histoplasmosis and tuberculosis
Deficiency of body iron stores, microcytic anemia
Lipid or glycogen storage disease
Myelodysplastic syndrome is the name of a group of conditions that occur when blood-forming cells in the bone marrow are damaged.
Interventions
Pretest Patient Care
Observe standard precautions.
Instruct the patient about test procedure, purpose, benefits, and risks.
Ensure that a legal consent form is properly signed and witnessed. Bone marrow aspiration is usually contraindicated in the presence of hemophilia and other bleeding dyscrasias.
Reassure the patient that analgesics will be available if needed. Administer moderate sedation and analgesia, if ordered. Use an oxygen monitor to evaluate breathing effectiveness.
Bone marrow biopsies or aspirations can be uncomfortable. Tell the patient that squeezing a pillow may be helpful as a distraction technique. Offer emotional support.
Sites used for bone marrow aspiration or biopsy affect pretest, intratest, and posttest care. Sites used include the posterosuperior iliac crest, anterior iliac crest (if the patient is very obese), sternum (not used as often with children because cavity is too shallow, danger of mediastinal and cardiac perforation is too great, and observation of procedure is associated with apprehension and lack of cooperation), vertebral spinous processes T10 through L4 and ribs, tibia (often in children), and ribs. Position the patient according to the site selected.
Explain to the patient the importance of remaining still during the procedure.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Monitor vital signs until stable and assess site for excess drainage or bleeding.
Recommend bed rest for 30 to 60 minutes; then, normal activities can be resumed.
Monitor for signs and symptoms of shock (increased heart rate and decreased blood pressure).
Assess for signs and symptoms of infections (redness, swelling, pain, and tenderness).
Administer analgesics or sedatives as necessary. Soreness over the puncture site for 3 to 4 days after the procedure is normal. Continued or severe pain may indicate fracture.
Review test results; report and record findings. Modify the nursing care plan as needed. Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
CLINICAL ALERT
Complications can include bleeding and sternal fractures. Osteomyelitis or injury to heart or great vessels is rare but can occur if the sternal site is used.
Manual and pressure dressings over the puncture site usually control excessive bleeding. Remove dressing in 24 hr. Redress site if necessary.
Fever, headache, unusual pain, or redness or pus at biopsy site may indicate infection (later event). Instruct patients to report these symptoms to their healthcare provider immediately.
The patient must remain still throughout this procedure.
BASIC BLOOD TEST
• Complete Blood Count (CBC)/Hemogram
A complete blood count (CBC), also referred to as a hemogram, consists of a WBC count, RBC count, Hb, Hct, RBC indices, and a platelet count. Table 2.2 contains the normal values for a CBC.
The CBC is a basic screening test and is one of the most frequently ordered laboratory procedures. The findings in the CBC give valuable diagnostic information about the hematologic and other body systems, prognosis, response to treatment, and recovery. The CBC consists of
a series of tests that determine number, variety, percentage, concentrations, and quality of blood cells:
a series of tests that determine number, variety, percentage, concentrations, and quality of blood cells:
WBC count: reports the total number of WBCs (leukocytes), which fight infection
Differential WBC count (Diff): identifies specific patterns of WBCs by percentage of each cell type (see Differential White Blood Cell Count [Diff; Differential Leukocyte Count] on page 67)
RBC count: reports the total number of RBCs, which carry O2 from lungs to blood tissues and CO2 from tissue to lungs
Hct: percentage of RBCs’ mass compared to the total volume of blood
Hb: main component of RBCs and transports O2 and CO2
RBC indices: calculated values of size and Hb content of RBCs; important in anemia evaluations
Mean corpuscular volume (MCV)
MCHC
Mean corpuscular hemoglobin (MCH)
Stained red cell examination (film or peripheral blood smear)
Platelet count (often included in CBC): Thrombocytes are necessary for clotting and control of bleeding
RBC distribution width (RDW): indicates degree variability and abnormal cell size
Mean platelet volume (MPV): index of platelet production
TABLE 2.2 Normal Values for Hemogram | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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These tests are described in detail in the following pages.
CLINICAL ALERTHct of <20% can lead to cardiac failure and death.
Hct of >60% is associated with spontaneous clotting of blood.
Hb value of <5.0 g/dL (<50 g/L) leads to heart failure and death.
Hb value of >20.0 g/dL (>200 g/L) results in hemoconcentration and clogging of capillaries.
A critical decrease in platelet value to <20 × 103/mm3 (<20 × 109/L) is associated with a tendency for spontaneous bleeding, prolonged bleeding time, petechiae, and ecchymosis.
Interfering Factors
RBC Count
Many physiologic variants affect outcomes: posture, exercise, age, altitude, pregnancy, and many drugs.
Hematocrit
Physiologic variants affect Hct outcomes: age, gender, and physiologic hydremia of pregnancy.
Hemoglobin
Physiologic variations affect test outcomes: high altitude, excessive fluid intake, age, pregnancy, and many drugs.
Mean Corpuscular Hemoglobin Concentration
High values may occur in newborns and infants.
Presence of leukemia or cold agglutinins may increase levels. Mean corpuscular hemoglobin concentration (MCHC) is falsely elevated with a high blood concentration of heparin.
MCH
Hyperlipidemia and high heparin concentrations falsely elevate MCH values.
WBC counts >50,000/mm3 falsely elevate Hb values and falsely elevate the MCH.
WBC Count
Hourly variation, age, exercise, pain, temperature, and anesthesia affect test results.
Neutrophils and Eosinophils
Physiologic conditions such as stress, excitement, exercise, and obstetric labor increase neutrophil levels. Steroid administration affects levels for up to 24 hours.
The eosinophil count is lowest in the morning and then rises from noon until after midnight. Do repeat tests at the same time every day. Stressful states such as burns, postoperative states, and obstetric labor decrease the count. Drugs such as steroids, epinephrine, and thyroxine affect eosinophil levels.
Platelets
Physiologic factors include high altitudes, strenuous exercise, excitement, and premenstrual and postpartum effects.
A partially clotted blood specimen affects the test outcome.
Interventions
Pretest Patient Care for Hemogram, CBC, and Differential (Diff) Count (All Components)
Explain test procedure. Explain that slight discomfort may be felt when skin is punctured. Refer to procedure for Venipuncture on page 52 for additional information.
Avoid stress, if possible, because altered physiologic status influences and changes normal hemogram values.
Select hemogram components ordered at regular intervals (e.g., daily, every other day). These should be drawn consistently at the same time of day for reasons of accurate comparison; natural body rhythms cause fluctuations in laboratory values at certain times of the day.
Dehydration or overhydration can dramatically alter values; for example, large volumes of IV fluids can “dilute” the blood, and values will appear as lower counts. The presence of either of these states should be communicated to the laboratory.
Fasting is not necessary. However, fat-laden meals may alter some test results because of lipidemia.
Some medications and other substances can alter results. Obtain a current medication history from the patient.
A high WBC count or diseases that cause RBCs to agglutinate may alter test results.
Posttest Patient Care for Hemogram, CBC, and Differential (Diff) Count (All Components)
Apply manual pressure and dressing to the puncture site on removal of the needle.
Monitor the puncture site for oozing. Maintain pressure dressings on the site if necessary. Notify the healthcare provider of unusual problems with bleeding. If a hematoma develops, apply a compress. If the hematoma is large, assess pulses distal to the phlebotomy site.
Resume normal activities and diet.
Bruising at the puncture site is not uncommon. Signs of inflammation are unusual and should be reported if the inflamed area appears large, if red streaks develop, or if drainage occurs.
Evaluate the outcome and counsel the patient appropriately about anemia, polycythemia, risk for infection, and related blood disorders.
Monitor patients with serious platelet defects for signs and symptoms of gastrointestinal bleeding, hemolysis, hematuria, petechiae, vaginal bleeding, epistaxis, and bleeding from gums.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
CLINICAL ALERTNever apply a total circumferential dressing and wrap because this may compromise circulation and nerve function if constriction, from whatever cause, occurs.
TESTS OF WHITE BLOOD CELLS
• White Blood Cell (WBC) Count (Leukocyte Count)
WBCs (leukocytes) are divided into two main groups: granulocytes and agranulocytes. The granulocytes receive their name from the distinctive granules that are present in the cytoplasm of neutrophils, basophils, and eosinophils. However, each of these cells also contains a multilobed nucleus, which accounts for their also being called polymorphonuclear (PMN) leukocytes. In laboratory terminology, they are often called “polys” or PMNs. The agranulocytes, which consist of the lymphocytes and monocytes, do not contain distinctive granules and have nonlobular nuclei that are not necessarily spherical. The term mononuclear leukocytes is applied to these cells.
The endocrine system is an important regulator of the number of leukocytes in the blood. Hormones affect the production of leukocytes in the blood-forming organs, their storage and release from the tissue, and their disintegration. A local inflammatory process exerts a definite chemical effect on the mobilization of leukocytes. The life span of leukocytes varies from 13 to 20 days, after which the cells are destroyed in the lymphatic system; many are excreted from the body in fecal matter.
Leukocytes fight infection and defend the body by a process called phagocytosis, in which the leukocytes actually encapsulate foreign organisms and destroy them. Leukocytes also produce, transport, and distribute antibodies as part of the immune response to a foreign substance (antigen).
The WBC count serves as a useful guide to the severity of a disease process. Specific patterns of leukocyte response can be expected in various types of diseases as determined by the differential count (showing percentages of each of the different types of leukocytes). Leukocyte and differential counts, by themselves, are of little value as aids to diagnosis unless the results are related to the clinical condition of the patient—only then is a correct and useful interpretation possible. Signs and symptoms of increased WBCs include fever, bruising, petechiae, fatigue, anemia, bleeding of mucous membranes, weight loss, and frequent infections.
Normal Findings
Black adults: 3.2 to 10.0 × 103 cells/mm3 or × 109/L or 3200 to 10,000 cells/mm3
Adults: 4.5 to 10.5 × 103 cells/mm3 or × 109/L or 4500 to 10,500 cells/mm3
Children:
0 to 2 weeks: 9.0 to 30.0 × 103 cells/mm3 or × 109/L or 9000 to 30,000 cells/mm3
2 to 8 weeks: 5.0 to 21.0 × 103 cells/mm3 or × 109/L or 5000 to 21,000 cells/mm3
2 months to 6 years: 5.0 to 19.0 × 103 cells/mm3 or × 109/L or 5000 to 19,000 cells/mm3
6 to 18 years: 4.8 to 10.8 × 103 cells/mm3 or × 109/L or 4800 to 10,800 cells/mm3
CLINICAL ALERT
WBC count <500/mm3 or <0.5 × 103/mm3 (or × 109/L) is extremely serious and can be fatal.
WBC count <2.0 × 109/L represents a critical value.
WBC count >30,000/mm3 or >30.0 × 103/mm3 (or × 109/L) is a critical value.
NOTE
Normal values vary greatly; check with your reference laboratory.
Procedure
Obtain a venous anticoagulated EDTA (lavender-topped tube) whole blood sample of 5 mL or a finger stick sample.
Label the specimen with the patient’s name, date and time of collection, and test(s) ordered.
Blood is processed either manually or automatically, using an electronic counting instrument such as the Coulter Counter® or Abbott CELL-DYN®.
Clinical Implications
Leukocytosis: WBC count >11,000/mm3 or >11.0 × 103/mm3 (or >11 × 109/L)
Leukocytosis is usually caused by an increase of only one type of leukocyte, and it is given the name of the type of cell that shows the main increase:
Neutrophilic leukocytosis or neutrophilia
Lymphocytic leukocytosis or lymphocytosis
Monocytic leukocytosis or monocytosis
Basophilic leukocytosis or basophilia
Eosinophilic leukocytosis or eosinophilia
An increase in circulating leukocytes is rarely caused by a proportional increase in leukocytes of all types. When this does occur, it is usually a result of hemoconcentration.
In certain diseases (e.g., measles, pertussis, sepsis), the increase of leukocytes is so great that the blood picture suggests leukemia. Leukocytosis of a temporary nature (leukemoid reaction) must be distinguished from leukemia. In leukemia, the leukocytosis is chronic and progressive.
Leukocytosis occurs in acute infections, in which the degree of increase of leukocytes depends on severity of the infection, patient’s resistance, patient’s age, and marrow efficiency and reserve.
Other causes of leukocytosis include the following:
Leukemia, myeloproliferative disorders
Trauma or tissue injury (e.g., surgery)
Malignant neoplasms, especially bronchogenic carcinoma
Toxins, uremia, coma, eclampsia, thyroid storm
Drugs, especially ether, chloroform, quinine, epinephrine (adrenaline), colony-stimulating factors
Acute hemolysis
Hemorrhage (acute)
After splenectomy
Polycythemia vera
Tissue necrosis
Occasionally, leukocytosis is found when there is no evidence of clinical disease. Such findings suggest the presence of:
Sunlight, ultraviolet irradiation
Physiologic leukocytosis resulting from excitement, stress, exercise, pain, cold or heat, anesthesia
Nausea, vomiting, seizures
Steroid therapy modifies the leukocyte response.
When corticotropin (adrenocorticotropic hormone [ACTH]) is given to a healthy person, leukocytosis occurs.
When ACTH is given to a patient with severe infection, the infection can spread rapidly without producing the expected leukocytosis; therefore, what would normally be an important sign is obscured.
Leukopenia: WBC count <4000/mm3 or <4.0 × 103/mm3 or <4.0 cells × 109/L occurs during and following:
Viral infections, some bacterial infections, overwhelming bacterial infections
Hypersplenism
Bone marrow depression caused by heavy metal intoxication, ionizing radiation, drugs:
Antimetabolites
Barbiturates
Benzene
Antibiotics
Antihistamines
Anticonvulsants
Antithyroid drugs
Arsenicals
Cancer chemotherapy (causes a decrease in leukocytes; leukocyte count is used as a link to disease)
Cardiovascular drugs
Diuretics
Analgesics and anti-inflammatory drugs
Primary bone marrow disorders
Leukemia (aleukemic)
Pernicious anemia
Aplastic anemia
Myelodysplastic syndromes
Congenital disorders
Kostmann’s syndrome
Reticular agenesis
Cartilage-hair hypoplasia
Shwachman-Diamond syndrome
Chédiak-Higashi syndrome
Immune-associated neutropenia
Marrow-occupying diseases (fungal infection, metastatic tumor)
Pernicious anemia
Interfering Factors
Hourly rhythm: There is an early-morning low level and late-afternoon peak. Age, gender, exercise, medications, pregnancy, pain, temperature, altitude, and anesthesia affect test results.
Age: In newborns and infants, the WBC count is high (10,000/mm3 to 20,000/mm3 or 10 × 109/L to 20 × 109/L); the count gradually decreases in children until the adult values are reached between 18 and 21 years of age.
Any stressful situation that leads to an increase in endogenous epinephrine production and a rapid rise in the leukocyte count
Interventions
Pretest Patient Care
Explain test purpose and procedure. Assess for signs and symptoms of increased WBCs (e.g., fever, bruising, petechiae, fatigue, anemia, bleeding of mucous membranes, weight loss, history of infections).
Refer to standard pretest care for hemogram, CBC, and differential count on page 63. Also, follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Select hemogram components ordered at regular intervals (e.g., daily, every other day). These should be drawn consistently at the same time of day for reasons of accurate comparison; natural body rhythms cause fluctuations in laboratory values at certain times of the day.
Dehydration or overhydration can dramatically alter values; for example, large volumes of IV fluids can “dilute” the blood, and values will appear as lower counts. The presence of either of these states should be communicated to the laboratory.
Fasting is not necessary. However, fat-laden meals may alter some test results as a result of lipidemia.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed. Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment.
Refer to standard posttest care for hemogram, CBC, and differential count on page 67. Also, follow guidelines in Chapter 1 for safe, effective, informed posttest care.
In prolonged severe granulocytopenia or pancytopenia:
Give no fresh fruits or vegetables because the kitchen, especially in a hospital, may be a source of food contamination.
When the WBC count is low, a person can get a bacterial, pseudomonal, or fungal infection from fresh fruits and vegetables.
Use a minimal-bacteria or commercially sterile diet. All food must be served from a new or single-serving package.
Consider a leukemia diet. See dietary department for restrictions (e.g., cooked food only) and careful food preparation.
Do not give intramuscular injections.
Do not take rectal temperature, give suppositories, give enemas, or perform rectal exams.
Do not allow patients to floss their teeth.
Do not use razor blades.
Do not give aspirin or NSAIDs, which cause platelet dysfunction.
Observe closely for signs or symptoms of infection; often, patients have only a fever. Without leukocytes to produce inflammation, serious infections can have very subtle findings.
Possible treatments include administration of blood products as ordered, assisting the patient with activities of daily living to decrease fatigue, and close monitoring for signs of infections. Also, provide frequent mouth care and promote hygiene.
• Differential White Blood Cell Count (Diff; Differential Leukocyte Count)
The total count of circulating WBCs is differentiated according to the five types of leukocytes, each of which performs a specific function.
The differential count is expressed as a percentage of the total number of leukocytes (WBCs). The distribution (number and type) of cells and the degree of increase or decrease are diagnostically significant. The percentages indicate the relative number of each type of leukocyte in the blood. The absolute count of each type of leukocyte is obtained mathematically by multiplying its relative percentage by the total leukocyte count. The formula is:
Relative value (%) × WBC (cells/mm3) = Absolute value (cells/mm3)
NOTE
This is the preferred way of reporting.
Function of Circulating White Blood Cells According to Leukocyte Type | ||||||||||||
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The differential count alone has limited value; it must always be interpreted in relation to the WBC count. If the percentage of one type of cell is increased, it can be inferred that cells of that type are relatively more numerous than normal, but it is not known whether this reflects an actual increase in the (absolute) number of cells that are relatively increased or an absolute decrease in cells of another type. On the other hand, if the relative (percentage) values of the differential count and the total WBC count are both known, it is possible to calculate absolute values that are not subject to misinterpretation.
Historically, a differential count was done manually, but current hematology instruments do an automated differential count. The count is based on a combination of hydrodynamic focusing and fluorescent dyes in newer instrumentation. However, not all samples can be evaluated by automated methods. When a leukocyte count is extremely low or high, a manual count may be necessary. Extremely abnormal leukocytes, such as those in leukemia, also have to be counted by hand. The automated instrument has built-in quality control that senses abnormal cells and flags the differential. A microscopic count must then be done.
• Segmented Neutrophils (Polymorphonuclear Neutrophils, PMNs, Segs, Polys)
Neutrophils, the most numerous and important type of leukocytes in the body’s reaction to inflammation, constitute a primary defense against microbial invasion through the process of phagocytosis. These cells can also cause some body tissue damage by their release of enzymes and endogenous
pyogens. In their immature stage of development, neutrophils are referred to as “stab” or “band” cells. The term band stems from the appearance of the nucleus, which has not yet assumed the lobed shape of the mature cell.
pyogens. In their immature stage of development, neutrophils are referred to as “stab” or “band” cells. The term band stems from the appearance of the nucleus, which has not yet assumed the lobed shape of the mature cell.
This test determines the presence of neutrophilia or neutropenia. Neutrophilia is an increase in the absolute number of neutrophils in response to invading organisms and tumor cells. Neutropenia occurs when too few neutrophils are produced in the marrow, too many are stored in the blood vessel margin, or too many have been called to action and used up.
Normal Findings
Absolute count: 3000 to 7000/mm3 or 3 to 7 × 109/L
African American adults: 1.2 to 6.6 × 109/L
Differential: 50% of total WBC count
0% to 3% of total PMNs are stab or band cells
NOTE
All references use this SI unit for reporting.
Procedure
Obtain a 5-mL blood sample in a lavender-topped tube (with EDTA); label the specimen with the patient’s name, date and time of collection, and test(s) ordered and place it in a biohazard bag.
Count as part of the differential.
Clinical Implications
Neutrophilia (increased absolute number and relative percentage of neutrophils) >8.0 × 109/L or 8000/mm3; for African Americans: >7.0 × 109/L or 7000/mm3
Acute, localized, and general bacterial infections. Also, fungal and spirochetal and some parasitic and rickettsial infections.
Inflammation (e.g., vasculitis, rheumatoid arthritis, pancreatitis, gout) and tissue necrosis (myocardial infarction, burns, tumors)
Metabolic intoxications (e.g., diabetes mellitus, uremia, hepatic necrosis)
Chemicals and drugs causing tissue destruction (e.g., lead, mercury, digitalis, venoms)
Acute hemorrhage, hemolytic anemia, hemolytic transfusion reaction
Myeloproliferative disease (e.g., myeloid leukemia, polycythemia vera, myelofibrosis)
Malignant neoplasms—carcinoma
Some viral infections (noted in early stages) and some parasitic infections
Ratio of segmented neutrophils to band neutrophils: normally, 1% to 3% of PMNs are band forms (immature neutrophils).
Degenerative shift to left: In some overwhelming infections, there is an increase in band (immature) forms with no leukocytosis (poor prognosis).
Regenerative shift to left: There is an increase in band (immature) forms with leukocytosis (good prognosis) in bacterial infections.
Shift to right: Decreased band (immature) cells with increased segmented neutrophils can occur in liver disease, megaloblastic anemia, hemolysis, drugs, cancer, and allergies.
Hypersegmentation of neutrophils with no band (immature) cells is found in megaloblastic anemias (e.g., pernicious anemia) and chronic morphine addiction.
Neutropenia (decreased neutrophils)
<1800/mm3 or <1.8 × 109/L
African Americans: <1000/mm3 or <40% of differential count
Causes associated with decreased or ineffective production
Inherited stem cell disorders and genetic disorders of cellular development
Acute overwhelming bacterial infections (poor prognosis) and septicemia
Viral infections (e.g., mononucleosis, hepatitis, influenza, measles)
Some rickettsial and parasitical (protozoan) diseases (malaria)
Drugs, chemicals, ionizing radiation, venoms
Hematopoietic diseases (e.g., aplastic anemia, megaloblastic anemias, iron-deficiency anemia, aleukemic leukemia, myeloproliferative diseases)
Causes associated with decreased survival
Infections mainly in persons with little or no marrow reserves, elderly people, and infants
Collagen vascular diseases with antineutrophil antibodies (e.g., systemic lupus erythematosus [SLE] and Felty’s syndrome)
Autoimmune and isoimmune causes
Drug hypersensitivity (There is an extensive list of drugs that continues to grow. Women are more likely than men to have a drug sensitivity. Removal of offending drug results in return to normal.)
Splenic sequestration
Neutropenia in neonates (<5000/mm3 or <5.0 × 109/L or <1000/mm3 or <1.0 × 109/L after first week of life)
Maternal neutropenia, maternal drug ingestion, maternal isoimmunization to fetal leukocytes (maternal immunoglobulin G [IgG] antibodies to fetal neutrophils)
Inborn errors of metabolism (e.g., maple syrup urine disease)
Immune deficits—acquired
Deficits and disorders of myeloid stem cell (e.g., Kostmann’s agranulocytosis, benign chronic granulocytopenia of childhood)
Congenital neutropenia
Pregnancy—progressive decrease until labor
Other leukocyte abnormalities and corresponding diseases are listed in Table 2.3.
NOTE
An ethnic difference exists only in neutrophils.
Interfering Factors
Physiologic conditions such as stress, excitement, fear, vomiting, electric shock, anger, joy, and exercise temporarily cause increased neutrophils. Crying babies have neutrophilia.
Obstetric labor and delivery cause neutrophilia. Menstruation causes neutrophilia.
Steroid administration: Neutrophilia peaks in 4 to 6 hours and returns to normal by 24 hours (in severe infection, expected neutrophilia does not occur).
Exposure to extreme heat or cold
Age
Children respond to infection with a greater degree of neutrophilic leukocytosis than adults do.
Some elderly patients respond weakly or not at all, even when infection is severe.
Resistance
People of any age who are weak and debilitated may fail to respond with a significant neutrophilia.
When an infection becomes overwhelming, the patient’s resistance is exhausted and, as death approaches, the number of neutrophils decreases greatly.
Myelosuppressive chemotherapy
Many drugs cause increases or decreases in neutrophils.
TABLE 2.3 Leukocyte Abnormalities and Diseases | ||||||||||||||||||||||||||||||||||||||||||
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Interventions
Pretest Patient Care
Explain test purpose and procedure.
Refer to standard pretest care for hemogram, CBC, and differential count on page 63. Also, follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed. Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment.
Monitor for neutrophilia or neutropenia.
Refer to standard posttest care for hemogram, CBC, and differential count on page 63. Also, follow guidelines in Chapter 1 for safe, effective, informed posttest care.
CLINICAL ALERTAgranulocytosis (marked neutropenia and leukopenia) is extremely dangerous and is often fatal because the body is unprotected against invading agents. Patients with agranulocytosis must be protected from infection by means of reverse isolation techniques with strictest emphasis on handwashing technique.
• Eosinophils
Eosinophils, capable of phagocytosis, ingest antigen-antibody complexes and become active in the later stages of inflammation. Eosinophils respond to allergic and parasitic diseases. Eosinophilic granules contain histamine (one third of all the histamine in the body).
This test is used to diagnose allergic infections, assess severity of infestations with worms and other large parasites, and monitor response to treatment.
Normal Findings
Absolute count: 0 to 0.7 × 109/L
Differential: 0% to 3% of total WBC count
Procedure
Obtain a 5-mL blood sample in a lavender-topped tube (with EDTA). Label the specimen with the patient’s name, date and time of collection (e.g., 3:00 p.m.), and test(s) ordered. Place it in a biohazard bag.
Perform a total WBC count, make a blood smear, count 100 cells, and report the percentage of eosinophils.
Be aware that an absolute eosinophil count is also available. It is done with a special eosinophil stain and manual counting on a hemacytometer. It must be done within 4 hours after collection or, if refrigerated, within 24 hours.
Clinical Implications
Eosinophilia (increased circulating eosinophils) >5% or >500 cells/mm3 or >0.5 × 109/L occurs in:
Allergies, hay fever, asthma
Parasitic disease and trichinosis tapeworm, especially with tissue invasion
Some endocrine disorders, Addison’s disease, hypopituitarism
Hodgkin’s disease and myeloproliferative disorders, chronic myeloid leukemia, polycythemia vera
Chronic skin diseases (e.g., pemphigus, eczema, dermatitis herpetiformis)
Systemic eosinophilia associated with pulmonary infiltrates (PIE)
Some infections (scarlet fever, chorea), convalescent stage of other infections
Familial eosinophilia (rare), hypereosinophilic syndrome
Polyarteritis nodosa, collagen vascular diseases (e.g., SLE), connective tissue disorders
Eosinophilic gastrointestinal diseases (e.g., ulcerative colitis, Crohn’s disease)
Immunodeficiency disorders (Wiskott-Aldrich syndrome, immunoglobulin A deficiency)
Aspirin sensitivity, allergic drug reactions
Löffler’s syndrome (related to Ascaris species infestation), tropical eosinophilia (related to filariasis)
Poisons (e.g., black widow spider, phosphorus)
Hypereosinophilic syndrome (>1.5 × 109/L), persistent extreme eosinophilia with eosinophilic infiltration of tissues causing tissue damage and organ dysfunction
Eosinophilic leukemia
Trichinosis invasion
Dermatitis herpetiformis
Idiopathic
Eosinopenia (decreased circulating eosinophils) is usually caused by an increased adrenal steroid production that accompanies most conditions of bodily stress and is associated with:
Cushing’s syndrome (acute adrenal failure): <50/mm3
Use of certain drugs such as ACTH, epinephrine, thyroxine, prostaglandins
Acute bacterial infections with a marked shift to the left (increase in immature leukocytes)
Eosinophilic myelocytes are counted separately because they have a greater significance, being found only in leukemia or leukemoid blood pictures.
Interfering Factors
Daily rhythm: Normal eosinophil count is lowest in the morning and then rises from noon until after midnight. For this reason, serial eosinophil counts should be repeated at the same time each day.
Stressful situations, such as burns, postoperative states, electroshock, and labor, cause a decreased count.
After administration of corticosteroids, eosinophils disappear.
See Appendix E for drugs that affect test outcomes.
Interventions
Pretest Patient Care
Explain test purpose and procedure.
Refer to standard patient care for hemogram, CBC, and differential count on page 63. Also, follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed. Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment.
Use special precautions if patient is receiving steroid therapy, epinephrine, thyroxine, or prostaglandins. Eosinophilia can be masked by steroid use.
Refer to standard posttest care for hemogram, CBC, and differential count on page 63. Also, follow guidelines in Chapter 1 for safe, effective, informed posttest care.
• Basophils
Basophils, which constitute a small percentage of the total leukocyte count, are considered phagocytic. The basophilic granules contain heparin, histamines, and serotonin. Tissue basophils are called mast cells and are similar to blood basophils. Normally, mast cells are not found in peripheral blood and are rarely seen in healthy bone marrow.
Basophil counts are used to study chronic inflammation. There is a positive correlation between high basophil counts and high concentrations of blood histamines, although this correlation does not imply cause and effect. It is extremely difficult to diagnose basopenia because a 1000 to 10,000 count differential would have to be done to get an absolute count.
Normal Findings
Absolute count: 15 to 50/mm3 or 0.02 to 0.05 × 109/L
Differential: 0% to 1.0% of total WBC count
Procedure
Obtain a 5-mL venous whole blood sample in a lavender-topped tube (with EDTA) and label the specimen with the patient’s name, date and time of collection, and test(s) ordered.
Count as part of the differential.
Clinical Implications
Basophilia (increased count) >50/mm3 or >0.05 × 109/L is commonly associated with the following:
Granulocytic (myelocytic) leukemia
Acute basophilic leukemia
Myeloid metaplasia, myeloproliferative disorders
Hodgkin’s disease
It is less commonly associated with the following:
Inflammation, allergy, or sinusitis
Polycythemia vera
Chronic hemolytic anemia
After splenectomy
After ionizing radiation
Hypothyroidism
Infections, including tuberculosis, smallpox, chickenpox, influenza
Foreign protein injection
Basopenia (decreased count) <20/mm3 or <0.02 × 109/L is associated with the following:
Acute phase of infection
Hyperthyroidism
Stress reactions (e.g., pregnancy, myocardial infarction)
After prolonged steroid therapy, chemotherapy, radiation
Hereditary absence of basophils
Acute rheumatic fever in children
Presence of numbers of tissue mast cells (tissue basophils) is associated with the following:
Interventions
Pretest Patient Care
Explain test purpose and procedure.
Refer to standard patient care for hemogram, CBC, and differential count on page 63. Also, follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed. Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment.
Use special precautions if patient is receiving steroid therapy, epinephrine, thyroxine, or prostaglandins. Eosinophilia can be masked by steroid use.
Refer to standard posttest care for hemogram, CBC, and differential count on page 63. Also, follow guidelines in Chapter 1 for safe, effective, informed posttest care.
• Monocytes (Monomorphonuclear Monocytes)
These agranulocytes, the largest cells of normal blood, are the body’s second line of defense against infection. Histiocytes, which are large macrophagic phagocytes, are classified as monocytes in a differential leukocyte count. Histiocytes and monocytes are capable of reversible transformation from one to the other.
These phagocytic cells of varying size and mobility remove injured and dead cells, microorganisms, and insoluble particles from the circulating blood. Monocytes escaping from the upper and lower respiratory tracts and the gastrointestinal and genitourinary organs perform a scavenger function, clearing the body of debris. These phagocytic cells produce the antiviral agent called interferon.
This test counts monocytes, which circulate in certain specific conditions such as tuberculosis, subacute bacterial endocarditis, and the recovery phase of acute infections.
Normal Findings
Absolute count: 100 to 500/mm3 or 0.1 to 0.5 × 109/L
Differential: 3% to 7% of total WBC count, or 0.03 to 0.07 of total WBC count
Procedure
Obtain a 5-mL whole blood sample in a lavender-topped tube (with EDTA) and label the specimen with the patient’s name, date and time of collection, and test(s) ordered.
Observe standard precautions.
Count as part of the differential.
Clinical Implications
In monocytosis: a monocyte increase of >500 cells/mm3 or >0.5 × 109/L or >10%. The most common causes are bacterial infections, tuberculosis, subacute bacterial endocarditis, and syphilis.
Other causes of monocytosis
Monocytic leukemia and myeloproliferative disorders
Carcinoma of stomach, breast, or ovary
Hodgkin’s disease and other lymphomas
Recovery state of neutropenia (favorable sign)
Lipid storage diseases (e.g., Gaucher’s disease)
Some parasitic, mycotic, and rickettsial diseases
Surgical trauma
Chronic ulcerative colitis, enteritis, and sprue
Collagen diseases and sarcoidosis
Tetrachloroethane poisoning
Phagocytic monocytes (macrophages) may be found in small numbers in the blood in many conditions:
Severe infections (sepsis)
Lupus erythematosus
Hemolytic anemias
Decreased monocyte count (<100 cells/mm3 or <0.1 × 109/L) is not usually identified with specific diseases:
Prednisone treatment
Hairy cell leukemia
Overwhelming infection that also causes neutropenia
HIV infection
Aplastic anemia (bone marrow injury)
Interventions
Pretest Patient Care
Explain test purpose and procedure.
Refer to standard pretest care for hemogram, CBC, and differential count on page 63. Also, follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed. Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment. Monitor for leukemia and infection.
Refer to standard posttest care for hemogram, CBC, and differential count on page 63. Also, follow guidelines in Chapter 1 for safe, effective, informed posttest care.
• Lymphocytes (Monomorphonuclear Lymphocytes); CD4, CD8 Count; Plasma Cells
Lymphocytes are small mononuclear cells without specific granules. These agranulocytes are motile cells that migrate to areas of inflammation in both early and late stages of the process. These cells are the source of serum immunoglobulins and of cellular immune response and play an important role in immunologic reactions. All lymphocytes are manufactured in the bone marrow. B lymphocytes mature in the bone marrow, and T lymphocytes mature in the thymus gland. B cells control the
antigen-antibody response that is specific to the offending antigen and is said to have “memory.” The T cells, the master immune cells, include CD4+ helper T cells, killer cells, cytotoxic cells, and CD8+ suppressor T cells.
antigen-antibody response that is specific to the offending antigen and is said to have “memory.” The T cells, the master immune cells, include CD4+ helper T cells, killer cells, cytotoxic cells, and CD8+ suppressor T cells.
Plasma cells (fully differentiated B cells) are similar in appearance to lymphocytes. They have abundant blue cytoplasm and an eccentric, round nucleus. Plasma cells are not normally present in blood.
This test measures the number of lymphocytes in the peripheral blood. Lymphocytosis is present in various diseases and is especially prominent in viral disorders. Lymphocytes and their derivatives, the plasma cells, operate in the immune defenses of the body.
Normal Findings
Lymphocytes: 25% to 40% of total leukocyte count (relative value) or 1500 to 4000 cells/mm3 or 1.5 to 4.0 × 109/L
Plasma cells: 0% or none
CD4 count: total WBC count × lymphocytes (%) × lymphocytes (%) stained with CD4
CD4/CD8 ratio: >1.0
Procedure
Obtain 5 mL of whole blood in a lavender-topped tube (with EDTA). Label the specimen with the patient’s name, date and time of collection, and test(s) ordered.
Count lymphocytes as part of the differential count.
Clinical Implications
Lymphocytosis: >4000/mm3 or >4.0 × 109/L in adults; >7200/mm3 or >7.2 × 109 in children; and >9000/mm3 or >9.0 × 109/L in infants occurs in:
Lymphatic leukemia (acute and chronic) lymphoma
Infectious lymphocytosis (occurs mainly in children)
Infectious mononucleosis
Caused by Epstein-Barr virus
Most common in adolescents and young adults
Characterized by atypical lymphocytes (Downey cells) that are large and deeply indented, with deep blue (basophilic) cytoplasm
Differential diagnosis—positive heterophil test
Other viral diseases
Viral infections of the upper respiratory tract (pneumonia)
Cytomegalovirus
Measles, mumps, chickenpox
Acute HIV infection
Infectious hepatitis (acute viral hepatitis)
Toxoplasmosis
Some bacterial diseases such as tuberculosis, brucellosis (undulant fever), and pertussis
Crohn’s disease, ulcerative colitis (rare)
Serum sickness, drug hypersensitivity
Hypoadrenalism, Addison’s disease
Thyrotoxicosis (relative lymphocytosis)
Neutropenia with relative lymphocytosis
Lymphopenia: <1000 cells/mm3 or <1.0 × 109/L in adults; <2500 cells/mm3 or <2.5 × 109/L in children occurs in:
Chemotherapy, radiation treatment, immunosuppressive medications
After administration of ACTH or cortisone (steroids); with ACTH-producing pituitary tumors
Increased loss through gastrointestinal tract owing to obstruction of lymphatic drainage (e.g., tumor, Whipple’s disease, intestinal lymphectasia)
Aplastic anemia
Hodgkin’s disease and other malignancies
Inherited immune disorders, AIDS, and AIDS immune dysfunction
Advanced tuberculosis (“miliary” tuberculosis), renal failure, SLE
Severe debilitating illness of any kind
Congestive heart failure
CD4 count: The number of CD+ lymphocytes is equal to the absolute number of lymphocytes (total WBC count × differential [%] of lymphocytes) times the percentage of lymphocytes staining positively for CD4. A severely depressed CD4 count is the single best indicator of imminent opportunistic infection.
Decreased CD4 lymphocytes
Immune dysfunction, especially AIDS. For the CD4, the diagnosis of AIDS is made for counts <200. There is a 1:3 ratio between Hb and Hct.
Acute minor viral infections
Increased CD4 lymphocytes
Therapeutic effect of drugs
Diurnal variation: Peak evening values may be two times morning values.
Plasma cells (not normally present in blood) are increased in:
Plasma cell leukemia
Multiple myeloma
Hodgkin’s disease
Chronic lymphatic leukemia
Cancer of liver, breast, prostate
Cirrhosis
Rheumatoid arthritis, SLE
Serum reaction
Some bacterial, viral, and parasitic infections
Abnormal Lymphocytes | ||||||
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Interfering Factors
Physiologic pediatric lymphocytosis is a condition in newborns that includes an elevated WBC count and abnormal-appearing lymphocytes that can be mistaken for malignant cells.
Exercise, emotional stress, and menstruation can cause an increase in lymphocytes.
African Americans normally have a relative (not absolute) increase in lymphocytes.
See Appendix E for drugs that affect outcomes.
Interventions
Pretest Patient Care
Explain test purpose and procedure.
Refer to standard pretest care for hemogram, CBC, and differential count. Also, follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed. Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment. Monitor for lymphocytosis or lymphopenia.
Refer to standard posttest care for hemogram, CBC, and differential count. Also, follow guidelines in Chapter 1 for safe, effective, informed posttest care.
CLINICAL ALERTA decreased lymphocyte count of <500/mm3 (<0.5 × 109/L) means that a patient is dangerously susceptible to infection, especially viral infections. Institute measures to protect the patient from infection.
• Lymphocyte Immunophenotyping (T and B Cells)
Lymphocytes are divided into two categories, T and B cells, according to their primary function within the immune system. In the body, T and B cells work together to help provide protection against infections, oncogenic agents, and foreign tissue, and they play a vital role in regulating self-destruction or autoimmunity.
Most circulating lymphocytes are T cells with a life span of months to years. The life span of B cells is measured in days. B cells (antibody) are considered bursa or bone marrow dependent and are responsible for humoral immunity (in which antibodies are present in the serum). T cells (cellular) are thymus derived and are responsible for cellular immunity. T cells are further divided into helper T (CD3+, CD4+) cells and suppressor T (CD3+, CD8+) cells.
Evaluation of lymphocytes in the clinical laboratory is performed by quantitation of the lymphocytes and their subpopulations and by assessment of their functional activity. These laboratory analyses have become an essential component of the clinical assessment of two major disease states: lymphoproliferative states (e.g., leukemia, lymphoma), in which characterization of the malignant cell in terms of lineage and stage of differentiation provides valuable information to the oncologist to guide prognosis and appropriate therapy; and immunodeficient states (e.g., HIV infection, organ transplantation), in which the alterations in the immune system that occur secondary to infection are evaluated.
The method of lymphocyte quantitation and characterization is based on the detection of cell surface markers by very specific monoclonal antibodies. For cell surface immunophenotyping, flow cytometry has become the method of choice. Cell surface phenotyping is accomplished by reacting cells from an appropriate specimen with one or more labeled monoclonal antibodies and passing them through a flow cytometer, which counts the proportion of labeled cells.
Normal Findings for Adult Peripheral Blood by Flow Cytometry
T and B surface markers:
Total T cells (CD3+): 53% to 88%
Helper T cells (CD3+, CD4+): 32% to 61%
Suppressor T cells (CD3+, CD8+): 18% to 42%
B cells (CD19+): 5% to 20%
Natural killer cells (CD16+): 4% to 32%
Absolute counts (based on pathologist’s interpretation):
Total lymphocytes: 660 to 4600/mm3 (0.6 to 4.6 × 109/L)
Total T cells (CD3+): 812 to 2318/mm3
Helper T cells (CD3+, CD4+): 589 to 1505/mm3
Suppressor T cells (CD3+, CD8+): 325 to 997/mm3
B cells (CD19+): 92 to 426/mm3
Natural killer cells (CD16+): 78 to 602/mm3
Lymphocyte ratio:
Helper-to-suppressor T-cell ratio >1.0
Procedure
Obtain 5 mL of whole blood in a lavender-topped tube (with EDTA). Label the specimen with the patient’s name, date and time of collection, and test(s) ordered.
Do not refrigerate or freeze the sample; it should remain at room temperature until testing is performed. Collect a separate 5-mL venous EDTA-anticoagulated blood sample for hematology at the same time. Because the interpretation of data is based on absolute values, it is imperative that a WBC count and differential count also be performed so that the appropriate data can be obtained.
Clinical Implications
Standard immunosuppressive drug therapy usually decreases lymphocyte totals.
Patients with an absolute helper T-lymphocyte count of <200/mm3 are at greatest risk for developing clinical AIDS.
Decreased T cells occur in congenital immunodeficiency diseases (e.g., DiGeorge’s syndrome, thymic hypoplasia).
Decreased T cells occur in kidney and heart transplant recipients receiving OKT-3, an immunomodulatory drug used to prevent rejection.
A marked increase in B cells occurs in lymphoproliferative disorders (e.g., chronic lymphocytic leukemia). In the typical case of chronic lymphocytic leukemia, the B cells would be positive for either κ or λ light chains (indicating monoclonality) and would express CD19 (a B-cell antigen).
Interventions
Pretest Patient Care
Explain purpose and specimen collection procedure. A recent viral cold can cause a decrease in total T cells, as can medications such as corticosteroids. Nicotine and strenuous exercise have also been shown to decrease lymphocyte counts.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed.
Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment. Lymphocyte immunophenotyping is performed to monitor patients who are HIV positive and have begun medication treatment. Transplantation patients are also retested at regular intervals to assess the threat of organ rejection or host infection. Also, see Chapter 8 for discussion of CD4 and CD8 cells.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
STAINS FOR LEUKEMIAS
Several special WBC staining methods are used to diagnose leukemia, amyloid disease, lymphoma, and erythroleukemia; to differentiate erythema myelosis from sideroblastic anemia; to monitor progress and response to therapy; and to detect early relapse. Amyloid refers to starchlike substances deposited in certain diseases (e.g., tuberculosis, osteomyelitis, leprosy, Hodgkin’s disease, and carcinoma).
• Sudan Black B (SBB) Stain
The Sudan Black B (SBB) stain aids in differentiation of the immature cells of acute leukemias, especially acute myeloblastic leukemia. The SBB stains a variety of fats and lipids that are present in myeloid leukemias but are not present in the lymphoid leukemias.
Reference Values
Positive Reactions
Granulocytic cells (neutrophils and eosinophils)
Myeloblasts
Promyelocytes
Neutrophilic myelocytes
Metamyelocytes, bands, and segmented neutrophils
Eosinophils at all stages
Monocytes and precursors
Variable Reactions
Basophils
Negative Reactions (Sudanophobia)
Lymphocytes and lymphocytic precursors
Megakaryocytes and thrombocytes (platelets)
Erythrocytes
Erythroblasts may display a few granules that represent mitochondrial phospholipid components.
Procedure
Obtain bone marrow aspirate.
Prepare slide, stain with SBB, and scan microscopically. Use normal smear control.
Clinical Implications
Positive staining of primitive (blast) cells indicates myelogenous origin of cells. SBB is positive in acute myelocytic leukemia (AML).
SBB is negative in acute lymphocytic leukemia, monocytic leukemia, plasma cell leukemia, and megakaryocytic leukemia.
SBB is weak to negative in acute monocytic leukemia.
Interfering Factors
There are cases of acute leukemia in which the cytochemical stains are not useful and fail to reveal the differentiating features of any specific cell line.
Interventions
Pretest Patient Care
Explain test purposes and procedures. If bone marrow aspiration is done, see pages 58-61 for special care.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed.
Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment. Monitor for leukemia, amyloid disease, anemia, and infection.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
• Periodic Acid-Schiff (PAS) Stain
The periodic acid-Schiff (PAS) stain aids in the diagnosis of acute lymphoblastic leukemia (ALL). Early myeloid precursors and erythrocyte precursors are negative. As granulocytes mature, they increase in PAS positivity, whereas mature RBCs stay negative. The PAS stain cannot be used to distinguish between ALL and AML or between benign and malignant lymphocytic disorders.
Normal Findings
Lymphoblasts: stain (positive)
Myeloblasts: do not stain (negative)
Procedure
Obtain bone marrow aspirate.
Prepare slide, stain with PAS, and scan microscopically.
Clinical Implications
Positive reaction
Blasts in ALL in childhood often have coarse clumps or masses of PAS-positive material within their scent cytoplasm. The staining pattern is usually heterogeneous, with some cells containing PAS-positive clumps and others virtually unstained.
Acute monocytic leukemia
Hairy cell leukemia
Sézary’s syndrome
Conspicuous PAS positivity in the erythroid precursors is strongly suggestive of erythroleukemia (M6).
Weakly positive
In acute granulocytic leukemia, the blasts display either a negative or weakly positive, finely granular pattern.
In some cases of thalassemia and in anemias with blocked or deficient iron, the RBC precursors also contain PAS-positive material.
Hodgkin’s lymphoma
Infectious mononucleosis
Negative stain
Lymphoblasts of Burkitt’s lymphoma
Megaloblastic leukemia
Interventions
Pretest Patient Care
Explain test purposes and procedures.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed. Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
• Terminal Deoxynucleotidyl Transferase (TDT) Stain
The thymus is the primary site of terminal deoxynucleotidyl transferase (TDT)-positive cells, and TDT is found in the nucleus of the more primitive T cells. A thymus-related population of TDT-positive cells resides in the bone marrow (normally a minor population, 0% to 2%). TDT is increased in >90% of cases of ALL of childhood. A minor (5% to 10%) population of patients with acute nonlymphoblastic leukemia has TDT-positive blasts. TDT-positive blasts are prominent in some cases of chronic myelogenous leukemia (CML), relating to the development of an acute blast phase. TDT has been reported to assist in establishing the diagnosis of ALL. TDT-positive cases of blast-phase CML correlate with a positive response to chemotherapy (vincristine and prednisone).
Normal Findings
Negative in nonlymphoblastic leukemia
Negative in peripheral blood
0% to 2% positive in bone marrow
Procedure
Obtain a 5-mL EDTA-anticoagulated peripheral blood sample or a 2-mL EDTA-anticoagulated bone marrow aspirate. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered.
Dry slides (store at room temperature for up to 5 days), process, and stain and then examine under the microscope for positive cells.
Clinical Implications
TDT is positive in ALL, lymphoblastic lymphoma, and CML (blast crisis).
TDT is negative in patients in remission and in those with CML or chronic lymphatic leukemia.
Interventions
Pretest Patient Care
Explain test purposes and procedures.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed. Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
• Leukocyte Alkaline Phosphatase (LAP) Stain
Neutrophils are the only leukocytes to contain various amounts of alkaline phosphatase.
The leukocyte alkaline phosphatase (LAP) stain is used as an aid to distinguish chronic granulocytic leukemia from a leukemoid reaction. A leukemoid reaction is a high WBC count that may look like leukemia but is not. In remission of CML, the LAP may return to normal. In the blast phase of CML, the LAP may be elevated.
Normal Findings
40 to 100 LAP units
NOTE
Normal values vary greatly; check with your reference laboratory.
Procedure
Obtain specimen by capillary puncture, venous whole blood (EDTA), green-topped tube. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered.
Prepare smear and air-dry; stain with LAP.
Make a count of 100 granulocytes and score (from 0 to 4+) as to the degree of LAP units.
Clinical Implications
Decreased values (0 to 15 LAP units)
CML
Paroxysmal nocturnal hemoglobinuria (PNH)
Idiopathic thrombocytopenic purpura
Hereditary hypophosphatasia
Progressive muscular dystrophy
Marked eosinophilia
Nephrotic syndrome
Siderocytic anemia
Increased values
Leukemoid reactions, all kinds of neutrophilia with elevated WBC count
Polycythemia vera
Thrombocytopenia (essential)
Down syndrome (trisomy 21)
Multiple myeloma
Hodgkin’s disease
Hairy cell leukemia
Aplastic leukemia, acute and chronic lymphatic leukemia, chronic granulocytic leukemia
Myelofibrosis, myeloid metaplasia
Normal levels of LAP
Secondary polycythemia
Hemolytic anemia
Infectious mononucleosis
Iron-deficiency anemia
Viral hepatitis
Serial LAP tests can be a useful adjunct in evaluating the activity of Hodgkin’s disease and the response to therapy.
Interfering Factors
Any physiologic stress, such as third-trimester pregnancy, labor, or severe exercise, causes an increased LAP score.
Steroid therapy increases LAP score.
CML with infection increases LAP score.
Interventions
Pretest Patient Care
Explain test purposes and procedures.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed.
Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment. Monitor for blood diseases.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
• Tartrate-Resistant Acid Phosphatase (TRAP) Stain
The malignant mononuclear cells of leukemic reticuloendotheliosis (hairy cell leukemia) are resistant to inhibition by tartaric acid. There is evidence that the reaction is not entirely specific because tartrate-resistant acid phosphatase (TRAP) reactions have been reported in prolymphocytic leukemia and malignant lymphoma and in some cases of infectious mononucleosis.
Normal Findings
No TRAP activity
Procedure
Obtain venous blood sample (5 mL) or bone marrow smear. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered.
Incubate blood smear with TRAP, counterstain, and examine microscopically.
Clinical Implications
TRAP is present in the leukemic cells of most patients with hairy cell leukemia; 5% of patients with otherwise typical hairy cell leukemia lack the enzyme.
TRAP occasionally occurs in malignant cells of patients with lymphoproliferative disorders other than hairy cell leukemia.
Histiocytes have weakly positive reactions.
Interventions
Pretest Patient Care
Explain test purposes and procedures. Assess for history of signs and symptoms of leukemia.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed. Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
TESTS FOR RED BLOOD CELLS
Many tests look at the RBCs: their number and size, amount of Hb, rate of production, and percent composition of the blood. The RBC count, Hct, and Hb are closely related but different ways to look at the adequacy of erythrocyte production. The same conditions cause an increase (or decrease) in each of these indicators.
• Red Blood Cell (RBC) Count (Erythrocyte Count)
The main function of the RBC (erythrocyte) is to carry oxygen from the lungs to the body tissues and to transfer carbon dioxide from the tissues to the lungs. This process is achieved by means of the Hb in the RBCs, which combines easily with oxygen and carbon dioxide and gives arterial blood a bright red appearance. To enable use of the maximal amount of Hb, the RBC is shaped like a biconcave disk—this affords more surface area for the Hb to combine with oxygen. The cell also is able to change its shape when necessary to allow for passage through the smaller capillaries.
The RBC count, an important measurement in the evaluation of anemia or polycythemia, determines the total number of erythrocytes in a microliter (cubic millimeter) of blood.
Procedure
Obtain 5 mL of whole blood in a lavender-topped tube (with EDTA). Label the specimen with the patient’s name, date and time of collection, and test(s) ordered. Place the specimen in a biohazard bag.
Automated electronic devices are generally used to determine the number of RBCs.
Note patient age and time of day on the laboratory slip.
Clinical Implications
Decreased RBC values occur in:
Anemia, a condition in which there is a reduction in the number of circulating erythrocytes, the amount of Hb, or the volume of packed cells (Hct). Anemia is associated with cell destruction, blood loss, or dietary insufficiency of iron or of certain vitamins that are essential in the
production of RBCs. See Chart 2.1 (later in this chapter) for a classification of anemias based on their underlying mechanisms and the test for reticulocyte count for a discussion of the purpose and clinical implications of the reticulocyte count.
Disorders such as:
Hodgkin’s disease and other lymphomas
Multiple myeloma, myeloproliferative disorders, leukemia
Acute and chronic hemorrhage
Lupus erythematosus
Addison’s disease
Rheumatic fever
Subacute endocarditis, chronic infection
(This list is not meant to be all inclusive.)
Erythrocytosis (increased RBC count) occurs in:
Primary erythrocytosis
Polycythemia vera (myeloproliferative disorder)
Erythremic erythrocytosis (increased RBC production in bone marrow)
Secondary erythrocytosis
Renal disease
Extrarenal tumors
High altitude
Pulmonary disease
Cardiovascular disease
Alveolar hypoventilation
Hemoglobinopathy
Tobacco, carboxyhemoglobin
Relative erythrocytosis (decrease in plasma volume)
Dehydration (vomiting, diarrhea)
Gaisböck’s syndrome
TABLE 2.4 Normal Values for Red Blood Cells | |||||||||||||||||||||||||||||||||||
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CLINICAL ALERTRefer to pages 94-95 for a discussion of the combined clinical implications of increased and decreased RBC count, Hct, and Hb values (polycythemia and anemia, respectively).
Interfering Factors
Posture: When a blood sample is obtained from a healthy person in a recumbent position, the RBC count is 5% lower. (If the patient is anemic, the count will be lower still.)
Dehydration: Hemoconcentration in dehydrated adults (caused by severe burns, untreated intestinal obstruction, severe persistent vomiting, or diuretic abuse) may obscure significant anemia.
Age: The normal RBC count of a newborn is higher than that of an adult, with a rapid drop to the lowest point in life at 2 to 4 months. The normal adult level is reached at age 14 years and is maintained until old age, when there is a gradual drop (see Table 2.4).
Falsely high counts may occur because of prolonged venous stasis during venipuncture.
Stress can cause a higher RBC count.
Altitude: The higher the altitude, the greater the increase in RBC count. Decreased oxygen content of the air stimulates the RBC count to rise (erythrocytosis).
Pregnancy: There is a relative decrease in RBC count when the body fluid increases in pregnancy, with the normal number of erythrocytes becoming more diluted.
There are many drugs that may cause decreased or increased RBC count. See Appendix E for drugs that affect test outcomes.
The EDTA blood sample tube must be at least three fourths filled or values will be invalid because of cell shrinkage caused by the anticoagulant.
The blood sample must not be clotted (even slightly) or the values will be invalid.
Interventions
Pretest Patient Care
Explain test purpose and procedure. Assess for signs/symptoms of fatigue, shortness of breath, weakness, tachycardia, and pallor of skin and mucous membranes.
Refer to standard pretest care for hemogram, CBC, and differential count.
Have the patient avoid extensive exercise, stress, and excitement before the test. These cause elevated counts of doubtful clinical value.
Avoid overhydration or dehydration, if possible—either causes invalid results. If patient is receiving IV fluids or therapy, note on requisition.
Note any medications the patient is taking.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed.
Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment. Monitor for anemia and erythrocytosis.
Refer to standard posttest care for hemogram, CBC, and differential count.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
Possible treatments include stop the source of bleeding, administer IV fluids, administer whole blood or packed cell infusions, give supplemental iron, and promote proper nutrition. Administer oxygen as ordered.
Resume normal activities and diet.
• Hematocrit (Hct); Packed Cell Volume (PCV)
The word hematocrit means “to separate blood,” which underscores the mechanism of the test because the plasma and blood cells are separated by centrifugation.
The Hct test is part of the CBC. This test indirectly measures the RBC mass. The results are expressed as the percentage by volume of packed RBCs in whole blood (packed cell volume [PCV]). It is an important measurement in the determination of anemia or polycythemia.
Normal Findings
Women: 36% to 48% or 0.36 to 0.48
Men: 42% to 52% or 0.42 to 0.52
Children:
0 to 2 weeks: 44% to 64% or 0.44 to 0.64
2 to 8 weeks: 39% to 59% or 0.39 to 0.59
2 to 6 months: 35% to 49% or 0.35 to 0.49
6 months to 1 year: 29% to 43% or 0.29 to 0.43
1 to 6 years: 30% to 40% or 0.30 to 0.40
6 to 16 years: 32% to 42% or 0.32 to 0.42
16 to 18 years: 34% to 44% or 0.34 to 0.44
NOTE
If blood is drawn from a capillary puncture and a microhematocrit is done, values are slightly higher.
CLINICAL ALERTAn Hct <20% (<0.20) can lead to cardiac failure and death; an Hct >60% (>0.60) is associated with spontaneous clotting of blood.
Procedure
Observe standard precautions. Obtain a 5-mL whole blood specimen in a lavender-topped tube (with EDTA). When doing a capillary puncture (finger puncture), the microcapillary tube is filled three fourths full with blood directly from the puncture site. These tubes are coated with an anticoagulative. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered.
Centrifuge the tubes in a microcentrifuge and measure the height of packed cells in the tube.
Record the measurement as a percentage of the total amount of blood in the capillary tube.
An Hct can be done on automated hematology instruments, in which case a 5-mL EDTA-anticoagulated venous blood sample is obtained.
Clinical Implications
Decreased Hct values are an indicator of anemia, a condition in which there is a reduction in the PCV. An Hct <30% (<0.30) means that the patient is moderately to severely anemic. Decreased values also occur in the following conditions:
Leukemias, lymphomas, Hodgkin’s disease, myeloproliferative disorders
Adrenal insufficiency
Chronic disease
Acute and chronic blood loss
Hemolytic reaction: This condition may be found in transfusion of incompatible blood or as a reaction to chemicals or drugs, infectious agents, or physical agents (e.g., severe burns, prosthetic heart valves).
The Hct may or may not be reliable immediately after even a moderate loss of blood or immediately after transfusion.
The Hct may be normal after acute hemorrhage. During the recovery phase, both the Hct and the RBC count drop markedly.
Usually, the Hct parallels the RBC count when the cells are of normal size. As the number of normal-sized erythrocytes increases, so does the Hct.
However, for the patient with microcytic or macrocytic anemia, this relationship does not hold true.
If a patient has iron-deficiency anemia with small RBCs, the Hct decreases because the microcytic cells pack to a smaller volume. The RBC count, however, may be normal or higher than normal.
Increased Hct values occur in:
Erythrocytosis
Polycythemia vera
Shock, when hemoconcentration rises considerably
CLINICAL ALERTRefer to pages 92-93 for a discussion of the combined clinical implications of increased and decreased Hct, Hb, and RBC values. The same underlying conditions cause an increase or decrease in each of these three tests of erythrocyte production.
Interfering Factors
People living at high altitudes have high Hct values as well as high Hb and RBC values.
Normally, the Hct slightly decreases in the physiologic hydremia of pregnancy.
The normal values for Hct vary with age and gender. The normal value for infants is higher because the newborn has many macrocytic red cells. Hct values in females are usually slightly lower than in males.
There is also a tendency toward lower Hct values in men and women older than 60 years of age, corresponding to lower RBC count values in this age group.
Severe dehydration from any cause falsely raises the Hct.
Interventions
Pretest Patient Care
Explain test purpose and procedure. Assess for signs/symptoms of fatigue, cool extremities, dyspnea, tachycardia, and pallor.
Refer to standard pretest care for hemogram, CBC, and differential count. Also, follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed.
Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment. Monitor for anemia or polycythemia.
Possible treatments may include administration of whole blood products, iron supplements, and proper nutrition. Also, supplemental oxygen may be ordered.
Refer to standard posttest care for hemogram, CBC, and differential count. Also, follow guidelines in Chapter 1 for safe, effective, informed posttest care.
• Hemoglobin (Hb)
Hb, the main component of erythrocytes, serves as the vehicle for the transportation of oxygen and carbon dioxide. It is composed of amino acids that form a single protein called globin, and a compound called heme, which contains iron atoms and the red pigment porphyrin. It is the iron pigment that combines readily with oxygen and gives blood its characteristic red color. Each gram of Hb can carry 1.34 mL of oxygen per 100 mL of blood. The oxygen-combining capacity of the blood is directly proportional to the Hb concentration rather than to the RBC count because some RBCs contain more Hb than others. This is why Hb determinations are important in the evaluation of anemia.
The Hb determination is part of a CBC. It is used to screen for disease associated with anemia, to determine the severity of anemia, to monitor the response to treatment for anemia, and to evaluate polycythemia.
Hb also serves as an important buffer in the extracellular fluid. In tissue, the oxygen concentration is lower, and the carbon dioxide level and hydrogen ion concentration are higher. At a lower pH, more oxygen dissociates from Hb. The unoxygenated Hb binds to hydrogen ion, thereby raising the pH.
As carbon dioxide diffuses into the RBC, carbonic anhydrase converts carbon dioxide to bicarbonate and protons. As the protons are bound to Hb, the bicarbonate ions leave the cell. For every bicarbonate ion leaving the cell, a chloride ion enters. The efficiency of this buffer system depends on the ability of the lungs and kidneys to eliminate, respectively, carbon dioxide and bicarbonate. Refer to the discussion of ABGs in Chapter 14.
As carbon dioxide diffuses into the RBC, carbonic anhydrase converts carbon dioxide to bicarbonate and protons. As the protons are bound to Hb, the bicarbonate ions leave the cell. For every bicarbonate ion leaving the cell, a chloride ion enters. The efficiency of this buffer system depends on the ability of the lungs and kidneys to eliminate, respectively, carbon dioxide and bicarbonate. Refer to the discussion of ABGs in Chapter 14.
Normal Findings
Women: 12.0 to 16.0 g/dL or 120 to 160 g/L
Men: 14.0 to 17.4 g/dL or 140 to 174 g/L
Children:
0 to 2 weeks: 14.5 to 24.5 g/dL or 145 to 245 g/L
2 to 8 weeks: 12.5 to 20.5 g/dL or 125 to 205 g/L
2 to 6 months: 10.7 to 17.3 g/dL or 107 to 173 g/L
6 months to 1 year: 9.9 to 14.5 g/dL or 99 to 145 g/L
1 to 6 years: 9.5 to 14.1 g/dL or 95 to 141 g/L
6 to 16 years: 10.3 to 14.9 g/dL or 103 to 149 g/L
16 to 18 years: 11.1 to 15.7 g/dL or 111 to 157 g/L
CLINICAL ALERTThe critical Hb value is <5.0 g/dL (<50 g/L), a condition that leads to heart failure and death. A value >20 g/dL (>200 g/L) leads to clogging of the capillaries as a result of hemoconcentration.
Procedure
Obtain 5 mL of whole blood in a lavender-topped tube (with EDTA). Fill the Vacutainer tube at least three fourths full. Automated electronic devices are generally used to determine the Hb; however, a manual colorimetric procedure is also widely used. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered.
Do not allow the blood sample to clot, or the results will be invalid. Place the specimen in a biohazard bag.
Clinical Implications
Decreased Hb levels are found in anemia states (a condition in which there is a reduction of Hb, Hct, or RBC values). The Hb must be evaluated along with the RBC count and Hct.
Iron deficiency, thalassemia, pernicious anemia, hemoglobinopathies
Liver disease, hypothyroidism
Hemorrhage (chronic or acute)
Hemolytic anemia caused by:
Transfusions of incompatible blood
Reactions to chemicals or drugs
Reactions to infectious agents
Reactions to physical agents (e.g., severe burns, artificial heart valves)
Various systemic diseases, including but not limited to:
Increased Hb levels are found in:
Polycythemia vera
Congestive heart failure
Chronic obstructive pulmonary disease (COPD)
Variation in Hb levels
Occurs after transfusions, hemorrhages, burns. (Hb and Hct are both high during and immediately after hemorrhage.)
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