This chapter presents information on common point-of-care (POC) tests and provider-performed microscopy (PPM) procedures.

POC testing is defined as medical testing at or near the site of patient care. POC tests are performed outside a central clinical laboratory using portable and hand-held devices and test kits or cartridges. PPM procedures are microscopic examinations performed by a healthcare provider during the course of a patient visit. PPM procedures involve using specimens that are labile and not easily transportable, or for which delay in performing the test could compromise the accuracy of the test result.

POC testing is considered as an integrated part of clinical laboratory service and is under the direction of the central laboratory. Physician interpretation of PPM findings (eg, direct wet mount preparation and KOH preparation) requires appropriate clinical privileges.

In the United States, test results can be used for patient care only when the tests are performed according to the requirements of the Clinical Laboratory Improvement Amendments of 1988 (CLIA ’88). These include personnel training and competence assessment before performing any test or procedure, following standard operating procedures and/or manufacturer instructions, performance and documentation of quality control for all tests, and participation in a proficiency testing program, if applicable.

Specimens should be collected and handled according to the institution’s policies and procedures.

1. 
   

   Safety Considerations

   
   

   General Safety Considerations

   
   

   Because all patient specimens are potentially infectious, the following precautions should be observed:

   
   
   
   
   
   
   1. 
      

      Universal body fluid and needle stick precautions must be observed at all times. Safety needle devices should be used.

   
   
   
   
   2. 
      

      Disposable medical gloves, gown, and sometimes mask, goggle, and face shield should be worn when collecting specimens.

   
   
   
   
   3. 
      

      Gloves must be changed and hands washed after contact with each patient. Dispose of gloves in an appropriate biohazard waste container.

   
   
   
   
   4. 
      

      Care should be taken not to spill or splash blood or other body fluids. Any spills should be cleaned up with freshly made 10% bleach solution.

   
   
   
   

   Handling and Disposing of Needles and Gloves

   
   
   
   
   
   
   1. 
      

      Do not resheathe needles.

   
   
   
   
   2. 
      

      Discard needles in a sharps container and gloves in a designated biohazard container.

   
   
   
   
   3. 
      

      Do not remove a used needle from a syringe by hand. The entire assembly should be discarded as a unit into a designated sharp container.

   
   
   
   
   4. 
      

      When obtaining blood cultures, it is unnecessary to change venipuncture needle when filling additional culture bottles.

   
   
   
   
2. 
   

   Specimen Handling

   
   

   Identification of Specimens

   
   
   
   
   
   
   1. 
      

      Identify the patient by having the patient state two identifiers (eg, full name plus date of birth or social security number) before obtaining any specimen.

   
   
   
   
   2. 
      

      Label each specimen tube or container with the patient’s name and unique identification number (eg, medical record number).

   
   
   
   

   Specimen Tubes: Standard specimen tubes that contain a vacuum (called evacuated tubes) are now widely available and are easily identified by the color of the stopper (see also Chapter 3). The following is a general guide:

   
   
   
   
   
   
   1. 
      

      Red-top tubes contain no anticoagulants or preservatives and are used for serum chemistry tests and certain serologic tests.

   
   
   
   
   2. 
      

      Serum separator tubes (SST) contain material that allows separation of serum and clot by centrifugation and are used for serum chemistry tests.

   
   
   
   
   3. 
      

      Lavender-top (purple) tubes contain EDTA and are used for hematology tests (eg, blood cell counts, differentials), blood banking (plasma), flow cytometry, and molecular diagnostic tests.

   
   
   
   
   4. 
      

      Green-top tubes contain heparin and are used for plasma chemistry tests and chromosome analysis.

   
   
   
   
   5. 
      

      Blue-top tubes contain sodium citrate and are used for coagulation tests.

   
   
   
   
   6. 
      

      Gray-top tubes contain sodium fluoride and are used for some chemistry tests (eg, glucose or alcohol requiring inhibition of glycolysis) if the specimen cannot be analyzed immediately.

   
   
   
   
   7. 
      

      Yellow-top tubes contain acid citrate dextrose (ACD) and are used for flow cytometry and HLA typing.

   
   
   
   

   Procedure

   
   

   Venipuncture is typically performed to obtain blood samples for acid-base and electrolyte studies, metabolic studies, hematologic studies, and coagulation studies. Arterial punctures are performed to obtain blood samples to assess arterial blood gases. Some tests (eg, glucose, rapid HIV test) can be performed on capillary blood obtained by puncturing the fingertip or heel using a lancet device.

   
   
   
   
   
   
   1. 
      

      When collecting multiple blood specimens by venipuncture, follow the recommended order of filling evacuated tubes, ie, blood culture bottles, coagulation tube (blue), non-additive tube (eg, plain red glass tube), SST, heparin tube (green), EDTA tube (lavender/purple), sodium fluoride tube (gray), and ACD tube (yellow). When using a butterfly collection device and drawing blood for a coagulation test, prime the tubing with a discard tube prior to specimen collection.

   
   
   
   
   2. 
      

      Fill each tube completely. Tilt each tube containing anticoagulant or preservative to mix thoroughly. Do not shake tube. Deliver specimens to the laboratory promptly.

   
   
   
   
   3. 
      

      For each of the common body fluids, Table 2–1 summarizes commonly requested tests and requirements for specimen handling and provides cross-references to tables and figures elsewhere in this book for help in interpretation of the results.

   
   
   
   

   Time to Test

   
   

   For most accurate results, samples should be tested immediately after collection. Samples are suitable for analysis for a limited time and thus should be tested within the time limits specified by the laboratory’s standard operating procedures.

POC testing is typically performed in a primary care clinic, physician office, emergency room, operating room, or intensive care unit. It is usually performed by non-laboratory personnel. Certain self-testing can also be performed by the patient at home.

Table 2–2 lists the commonly used POC tests, many of which are CLIA waived (waived from regulatory procedures).

Advantages of POC testing include: