Test

Normal Range

Limitations

Falsely Increased

Falsely Decreased

ACTH

<46 pg/mL

Significant diurnal variations, high in the morning (6-8 AM). Releases in bursts, levels vary by minute.

Pregnancy, menstruation, stress, rheumatoid factor

Patients taking glucocorticoids

Albumin

0-4 mo: 2.0-4.5 g/dL

4 mo-16 y: 3.2-5.2 g/dL

>16 y: 3.5-4.8 g/dL

Two dye-binding methods, bromocresol green (BCG) and bromocresol purple (BCP), are in routine use.

BCG overestimates albumin in serum due to poorer specificity for the analyte.

BCP underestimates in pediatric patients on hemodialysis and chronic renal failure.

Alkaline phosphatase

0-1 y: 150-350 IU/L

1-16 y: 30-300 IU/L

>16 y: 30-115 IU/L

Day-to-day variations (5-10%)

Higher in African American men (15%) and women (10%) compared to other racial/ethnic groups

Recent food ingestion, smoking, increased BMI (25%), drugs: penicillin, antiepileptic drugs, antihistamines, cardiovascular drugs

Use of oral contraceptives

AFP, tumor marker

0.6-6.60 ng/mL

Not recommended as a screening procedure to detect cancer in the general population

Tumors of the GI tract, liver damage (e.g., cirrhosis, hepatitis, or drug or alcohol abuse), and pregnancy

Smoking tobacco (10%)

Inflammatory bowel disease

Some dietary supplements, herbal remedies, and vitamins can cause liver toxicity, leading to a rise in AFP levels.

NA

Ammonia

<50 µmol/L

Not useful to assess the degree of dysfunction (e.g., in Reye syndrome, hepatic function improves and the ammonia level falls, even in patients who finally die of these disorders)

Levels are not always high in all patients with urea cycle disorders.

Atmospheric ammonia

The presence of ammonium ions in anticoagulants

High-protein diet, GI hemorrhage, increases due to cellular metabolism: 20% in 1 h and 100% by 2 h, prolonged tourniquet application

NA

ANA

Negative

Not recommended as a general screening test

Depending on the titer, normal healthy population can have 5-20% positive test results.

Drugs (carbamazepine, chlorpromazine, ethosuximide, hydralazine, isoniazid, mephenytoin, methyldopa, penicillins, phenytoin, primidone, procainamide, and quinidine)

Viral illness and infections

NA

Bilirubin total and direct

0-1 d: 0.0-6.0 mg/dL

1-2 d: 0.0-8.0 mg/dL

2-5 d: 0.0-12.0 mg/dL

5 d-4 mo: 0.3-1.2 mg/dL

>4 mo: 0.3-1.2 mg/dL

Direct bilirubin

0.0-0.4 mg/dL

Day-to-day variation (15-30%)

Lower in African Americans

Fasting up to 48 h

Exposure to light

Penicillin

Acetyl salicylic acid

Sulfisoxazole

Calcium, total

8.7-10.7 mg/dL

Need to interpret with total protein and albumin levels

0.8 mg of calcium is bound to 1.0-g albumin in serum. To correct, add 0.8 mg/dL for every 1.0 g/dL that serum albumin falls below 4.0 g/dL.

Hyperalbuminemia

Multiple myeloma

Waldenström macroglobulinemia

Dehydration

Venous stasis during blood collection by prolonged application of tourniquet

Hyponatremia (<120 mmol/L)

Hypomagnesemia

Hyperphosphatemia (e.g., laxatives, phosphate enemas, chemotherapy of leukemia or lymphoma, rhabdomyolysis)

Hypoalbuminemia

Hemodilution

CO₂, total

0-2 y: 20-25 mmol/L

2-16 y: 22-28 mmol/L

>16 y: 24-32 mmol/L

80-90% present as bicarbonate and is general guide to body’s buffering capacity

Antacids

Corticotrophin

Mercurial and thiazide diuretics

Sodium bicarbonate

Hyperthermia

Acetazolamide

Ammonium chloride, aspirin, chlorothiazide diuretics, methicillin

Paraldehyde, tetracycline

High altitudes

CA-125

0-35 U/mL

Not recommended for screening asymptomatic women

Not increased in mucinous adenocarcinoma

Different manufacturer assays do not produce similar value. Should not be used interchangeably.

Pregnancy

Menstruation, endometriosis

Pleural effusion or inflammation

Peritoneal effusion or inflammation, cirrhosis, severe liver necrosis (66%), disorders of the GI tract, liver, and pancreas

Renal failure, healthy persons (1%)

Postmenopausal women

African American and Asian women

Cholesterol, total

<200 mg/dL

Intraindividual variation (10%)

Seasonal variation (8%) higher in the winter than in summer

Positional variation is 5% and 10-15% lower when phlebotomized sitting or recumbent, respectively, as opposed to standing.

Pregnancy, drugs: beta blockers, anabolic steroids, vitamin D, oral contraceptives, and epinephrine

Smoking, alcohol, renal failure

Hypothyroidism, glycogen storage disease, biliary cirrhosis, hepatocellular disease

Prostate and pancreatic neoplasms

Acute illness such as a heart attack

Malnutrition

Liver disease

Myeloproliferative diseases

Chronic anemias

Infection

Hyperthyroidism

Stress

CRP

<10 mg/L

Not a screening test for wellness and should only be used in the diagnosis and monitoring of a patient who appears to have an inflammatory process

Elevated levels are nonspecific and should not be interpreted without a complete clinical history.

Influenced by genetics, age, and sedentary lifestyle, stress, exposure to environmental toxins, and diet that specifically contains refined, processed, and manufactured foods

Oral contraceptives

Pregnancy

Monoclonal gammopathy

Patients treated with carboxypenicillins

Liver failure

ESR

0-15 mm/h in men 0-20 mm/h in women

Not a good screening test

Compared to the ESR, CRP is a more sensitive and specific marker of the acute phase reaction and is more responsive to changes in the patient’s condition.

There are only two circumstances where the erythrocyte sedimentation rate is superior—detecting low-grade bone and joint infections and monitoring disease activity in systemic lupus erythematosus.

Increased fibrinogen; increased gamma- and beta globulins

Drugs (dextran, penicillamine, theophylline, vitamin A, methyldopa, methysergide)

Technical factors (e.g., hemolyzed sample, high temperature in the laboratory)

Hypercholesterolemia

Abnormally shaped RBCs (sickle cells, spherocytes, acanthocytes)

Microcytosis, HbC disease, hypofibrinogenemia

Technical factors (low temperature in the laboratory, clotted blood)

Extreme leukocytosis

Drugs (quinine, salicylates, high steroid levels, drugs that cause high glucose levels)

Ferritin

Male: 23-336 ng/mL (in patients with normal iron stores, it should be >30 ng/mL)

Female: 11-306 ng/mL

In hepatic, malignant, and inflammatory conditions, ferritin levels can be normal. In such cases, bone marrow stain of iron may be used to exclude iron deficiency.

Inflammation

Liver and kidney disease, malignancy

Obesity and age

Alcohol use

Vegetarianism

GGT

Sensitive but nonspecific indicator of biliary disease

Half-life (7-10 d); in alcoholassociated liver injury, the half-life is increased to as much as 28 d, suggesting impaired clearance.

Day-to-day variations (10-15%); approximately double in African Americans

Higher BMI (25-50%)

Renal disease

Cardiac disease

Phenytoin

Pregnancy (25%)

HCG

Negative

Approximately one third of all conceptions end in natural termination. This may produce positive results when testing early in the pregnancy followed by negative results after the natural termination.

Marijuana use

Human antimouse antibody (HAMA) or heterophilic antibody

Elevated LH levels due to low testosterone can lead to false positives.

Duodenal ulcers

Cirrhosis of the liver

Inflammatory bowel disease

Smoking tobacco (20%)

False negatives in urine tests can be caused by drinking large amounts of fluids and taking diuretics, anticonsultants, anti-Parkinson drugs, tranquilizers, hypnotics, or certain antihistamines before the test.

Lipase

0-50 U/L

More specific for pancreatitis than is for serum amylase; diagnosis of peritonitis, strangulated or infarcted bowel, pancreatic cyst

Cholinergic drugs, opiates

Alcohol

Renal disease

Macrolipasemia

Citrates

Intravenous dextrose

Oxalates

Saquinavir

PTH-intact

12-65 pg/mL

Inherent biologic variability due to hormone pulsatility and diurnal variation, choice of tube for sample collection, as well as sample stability at storage temperature

Because of a pronounced nocturnal rise in intact PTH levels observed in a small experimental male population, sampling after 10 AM for optimum discrimination between normal and those with mild primary hyperparathyroidism has been suggested.

Heterophile antibodies

Rheumatoid factor

Sedative-hypnotic drug propofol (Diprivan)

PSA

<4 ng/mL

Ambulatory values are higher than sedentary values, which may decrease ≤50% (mean = 18%).

Methodologic variations exist depending upon calibrators (WHO vs. Hybritech) used by various manufacturers (22% average bias).

Prostatic massage, ≤2 times

Cystoscopy: 4 times

Needle biopsy: >50 times for ≤1 mo

Transurethral resection: >50 times, digital rectal examination, indwelling catheter

Vigorous bicycle exercise: ≤2-3 times several days, ejaculation within 24-48 h

Urinary tract infection

Castration

Antiandrogen drugs (e.g., finasteride)

Radiation therapy

Prostatectomy

PSA falls 17% in 3 d after lying in hospital

TSH

0.5-6.3 µIU/mL, depending on age and sex

Not be useful for hospitalized ill patients. Has a diurnal rhythm (50%), with peaks at 2:00-4:00 AM and troughs at 5:00-6:00 PM with ultradian variations

Dopamine

Glucocorticoids

Rheumatoid factor

Human antimouse antibodies

Heterophile antibodies

Thyroid hormone autoantibodies

Macro-TSH

Severe dehydration

Biotin may cause falsely low values in immunometric assays.