Specimen Sampling
To ensure quality testing, it is important to adhere to the following general guidelines when preparing a specimen for testing. Once a specimen is collected properly, it must be processed, stored, and transported correctly or results may be compromised. If you are sending specimens to our laboratory for analysis, make certain that your specimen collection, handling, and transportation procedures meet the guidelines set by our laboratory.
Whole Blood
Whole blood is drawn into tubes that contain anticoagulant. After the tube is filled, it must be inverted at least 5-6 times to ensure adequate mixing and prevent coagulation. The entire tube must be submitted for testing, do not split specimens. The following are some of the tubes used for whole blood:
Blue top: sodium citrate (suggested concentration is 3.2%)Purple/lavender top: EDTA
Green top: heparin
Yellow top: SPS (for microbiology fluids and blood)
Yellow top: ACD Solution B (for genetic and chromosome analysis, flow cytometry)
Navy blue top: EDTA (for lead)
Gray top: potassium oxalate sodium fluoride
Be sure to distinguish between yellow top tubes used for genetic testing and those for microbiology, as they are not interchangeable. There are also several types of heparin tubes that may also contain sodium, lithium, or a gel separator. Navy blue EDTA tubes should not be confused with navy blue top tubes that contain no additives. Sodium citrate tubes used primarily for coagulation testing must be filled to the required volume of the tube in order to maintain the appropriate concentration of citrate anticoagulant in the plasma to be tested. Occasionally a red top tube is required for a whole blood specimen, in these cases do not use tubes containing gels or serum separators. Always consult our reference manual or on-line test catalog when in doubt of what type of tube is required for testing.
Plasma
Specimens are drawn into tubes that contain anticoagulant. The plasma is obtained by drawing a whole blood specimen with subsequent centrifugation to separate the plasma. After drawing the specified tube, invert 5-6 times to ensure adequate mixing and prevent coagulation. Some specimens may require immediate centrifugation, separation, and freezing. Others may need to be double centrifuged to completely remove platelets. Centrifuge 10 minutes at 3000 rpm. Transfer the plasma into a plastic transport tube. Clearly label specimens as "plasma " when the plasma has been separated prior to transport. It is important to distinguish between plasma and serum, as plasma contains clotting factors. Consult our reference manual or on-line test catalog for collection instructions of specific tests.
Serum
Specimens are drawn into tubes that contain no additives or anticoagulants. Serum is obtained by drawing the blood into a red top or serum separator tube, allowing it to clot, and centrifuging to separate the serum. Centrifuge for 10 minutes at 3000 rpm. Transfer the serum into a plastic transport tube. Do not use gel or serum separator tubes for drug levels as the drug may be absorbed into the gel. Hemolyzed, lipemic, or icteric specimens may cause erroneous results. Consult our reference manual before sending these specimens.
Urine
Urine specimens for routine urinalysis require 15 ml of urine in a screw-capped, plastic urine container, or collection kit supplied by UPHSM. Keep specimen refrigerated. 24-hour urines should be returned in the original collection container without aliquoting. Secure caps tightly to prevent leakage. Consult our reference manual for specimen volume and storage requirements for testing of random urines and urine aliquots.
Body Fluid - Fluid Count / Crystal Analysis
Sterile plastic CSF tubes are used for CSF fluids. There should be no delay in getting the specimen to the laboratory for testing, as RBC's will begin lysing in 1-2 hours and give inaccurate results for the presence of xanthochromia and for the RBC count. Likewise, WBC lysis also occurs and will give a false impression of the number of WBC's present.
All other types of fluids should be put into a green-top sodium heparin vacutainer tube. A bloody fluid that is put into a plain tube that contains no anticoagulant will most surely clot and result in inaccurate counts.
If crystals are ordered on a joint fluid, the specimen must be put into a green-top sodium heparin vacutainer tube. No other type of tube should be used. EDTA, lithium heparin, and oxalate can all produce crystalline structures resembling monosodium urate crystals.
Slides
Blood films must be labeled with the patient name and date using a pencil. Do not use stickers, ink pens, or markers to label slides. Send two unstained slides in a cardboard or plastic slide holder that is closed securely. Label the outside of the slide holder with the date, patient name, and date of birth or other identification number. Store and transport slides at ambient temperature.
Microbiology Specimens
Send microbiology specimens in the appropriate sterile container or transport device. Consult our reference manual about special transport media's and preservatives that may be necessary to enhance the recovery of certain organisms. Some microbiology tests require special specimen collection and transport conditions. When in doubt, please contact the Microbiology department with any questions you may have at 906-225-7795.
Aerobic routine cultures:
Body fluids, aspirates, washes, tissues, sputum: send specimen in a sterile screw-capped container. Forward promptly at ambient temperature.
Bronchial brush: place bronchial brush in brush wrapper and secure with tape. Forward promptly at ambient temperature.
Swab specimens: place swab in a Culturette transport tube and forward promptly at ambient temperature.
Urine: send 10 ml of urine in a sterile screw-capped container or urine culture transport tube with preservative. Keep specimen refrigerated.
Anaerobic cultures:
Body fluids or aspirates: send in a Cary Blair gel transport tube.
Tissues: send in a sterile screw-capped container.
Forward promptly at ambient temperature.
Stool specimens:
Inpatient specimens can be sent in a sterile screw-capped container. Reference lab and outpatient specimens must be sent as follows:
Stool culture: send 10ml of liquid stool or walnut-size stool specimen collected in a sterile screw-capped container with Cary Blair transport media. Forward at ambient temperature.
Ova and parasites: send stool in a screw-capped container with 10% formalin. Specimens suspected of containing parasite trophozoites, or requiring a trichrome slide should be sent in a PVA preservative also. Forward at ambient temperature.
Clostridium difficile Toxin A: send specimen in sterile screw-capped container with no preservative. Keep specimen refrigerated. If transport time will exceed 72 hours, specimen must be frozen.
Fungal cultures:
Send specimen in a sterile screw-capped container. Specimen can be refrigerated or stored at ambient temperature. Do not freeze. (Swab specimens are considered suboptimal for this type of culture.)
Mycobacterial cultures:
Send specimen in a sterile screw-capped container. Specimen can be stored at ambient temperature, refrigerated, or frozen. (Swab specimens are considered suboptimal for this type of culture.)
Viruses
Viral culture: send swab or fluid in a viral transport tube such as Bartels Viral Transport or MicroTest M4, supplied by our lab. Tissue can be sent in a sterile screw-capped container. CSF must be sent in a sterile screw capped container, do not transfer to viral media.
RSV antigen: swabs can be sent in a Culturette transport tube or in a viral transport tube. Aspirates and washes can be sent in a sterile screw-capped container or in a viral transport tube.
Influenza A/B: send swab in a Culturette transport tube. Send sputum in a sterile screw-capped container. Keep specimen refrigerated.
Send a separate specimen for each test. Rapid antigen swab specimens cannot be used for culture also.
Specimen labeling
Specimens must be labeled with the patient name, date of birth or medical record number, time and date of collection, and phlebotomist ID. The label on the specimen must match the information on the requisition. A specimen may be rejected due to improper labeling.
Storage and Transport Temperature
Specimens must be stored and transported at the temperature indicated in our reference manual. When ordering more than one test on a frozen sample, separate aliquots should be submitted for each test. Please indicate special temperature requirements to your courier to ensure that specimen integrity is maintained during transport.
Standard Order of Draw
Blood collection tubes must be drawn in a specific order to avoid cross-contamination of additives between tubes and to maintain sterility when blood cultures are drawn. The recommended order is as follows:
- Blood culture tube
- Non-additive tube
- Coagulation tube*
- Additive tubes in this order:
- Gel separator
- Heparin
- EDTA
- Oxalate / fluoride
*If only a coagulation tube is to be drawn for routine coagulation testing (PT and PTT), the first tube drawn may be used for testing. For special coagulation testing (e.g. Factor VIII) a non-additive tube should be drawn first.
Specimen Quality
Specimen quality is extremely important for accurate results. The following is a summary of specimen quality issues that must be taken into consideration when drawing, storing, and transporting blood specimens.
Hemolysis
Serum tubes should be centrifuged and separated promptly. Analytes such as glucose, potassium, LDH, Cholesterol, Creatinine, Iron, Phosphorous, Calcium, and most enzymes are affected by hemolysis and/or prolonged contact with the clot.
Hemolyzed specimens are not suitable for hematologic and coagulation testing.
Inadequate Draw – QNS
Hematology and coagulation tests require a full tube of blood. The ratio of anticoagulant is specific for the volume of specimen. Coagulation tests will not be performed on short-draws. Short draw hematology tubes will result in RBC crenation, reduced MCV and hematocrit, and possible changes in WBC morphology, platelet and total WBC count.
Clotted Specimens
All hematology and coagulation testing utilizes anticoagulated blood. Clots, large or small, will lead to erroneous results for these tests.
Lipemia
Lipemia can falsely elevate SGPT and SGOT. It can also affect the results for CBC’s. Be sure a patient has adequately fasted prior to collection, if needed.
Poor Preservation / Old Specimens
Hematology specimens need to be tested within 24 hours. Old specimens will yield unreliable cell counts and distorted cell morphology. Coagulation plasma should be centrifuged, separated, and stored appropriately until testing can be performed.
