How to Prevent Lab Testing Artifacts

Interpretation of blood profiles presents challenges to practitioners. Important factors relevant to interpretation include species, age, sex, history, previous therapy, diet, exposures. Veterinary diagnostic labs frequently process samples which add another dimension to the interpretation challenge: artifacts.
Artifacts are caused primarily by errors in collection, processing, and shipping. In addition patient factors can cause spurious values. These artifacts can render a normal panel with markedly out of range values or mask out of range values.

Blood Samples-Hematology

Blood collection techniques should be used to minimize patient contact time and stress. Blood volumes which can be safely taken include up to 1% of patient's body weight, which usually far exceed sampling requirements. Avian patients do not possess contractible spleens however stress hemograms (leukocytosis, heterophilia) are seen in excitable, stressed birds. We not recommend anesthesia for blood collection.
A blood film should always be made at collection time as soon as the needle is withdrawn from the vein. An air-dried, thin smear provides superior cellular morphology compared to samples stored in EDTA or heparin.The coverslip smear has provided superior smears, with a lower incidence of smudge cells. Using, two clean 22 by 22 millimeter glass coverslips, a drop of blood is placed on the center of one. Then the second coverslip is dropped onto the first and immediately glided past, before the blood spreads out.

Blood Samples-Chemistry

Samples for chemistry analysis should be submitted as plasma. That means collecting into heparinized capillary tubes or green top separator tubes. Centrifuge and harvest the plasma immediately. Serum samples, particularly from avian patients- are often problematic, due to fibrin.
Unseparated, clotted, or hemolyzed samples are frequent causes of spurious lab values. Samples for clinical chemistry analysis should never be placed or submitted in containers with EDTA which will invalidate calcium assays.
Lipemia is a normal physiologic event in ovulating birds. Lipemia can severely affect most photometric analyses. Ultracentrifugation or chemical treatment can help in reducing or removing the fat, allowing a reasonably reproducible value. Lipemia is also observed in certain pathologic states. Fasting is not usually necessary before blood sampling a bird. Fasting a lipemic bird is not advised, particularly if it is obviously ill.
Creatine kinase (CK, CPK) can easily elevate physiologically in the excitable or roughly handled pet bird. In ratites, the normal act of exercise, capture and restraint can result in markedly elevated values. Injections can also increase CK, particularly large bore needles, irritating drugs, and steroids.

Microbiology Samples

Vigorously sample the culture site. Swabs for bacterial/fungal culture should immediately go into appropriate transport media, activating the transport media if necessary. Tissue or material shipped in a tube is NOT ACCEPTABLE for culture due to overgrowth and cell death during shipment.
If gram-staining is planned in-house OR for submission, we recommend rolling the primary culture swab onto autoclaved microslides.
It is important to note the source of the sample as the laboratory work up relies on this information.

Chlamydia & Polyoma Samples

Chlamydia Antigen ELISA, Chlamydia DNA PCR swabs, or Polyoma DNA PCR swabs should be packaged after sampling. While organism viability is not a concern for these tests, environmental cross-contamination of PCR samples dictates that the swab is submitted in a sterile transport (non-agar) medium.
Chlamydia serology- plasma is preferred.

Viral Blood (PBFD, Polyoma) & Sex Testing, Lead Samples


Whole, unclotted heparinzed blood is recommended.

Cytology

Because of the national nature of our service, we do not provide fluid analysis. Our cytodiagnosis services are limited to microscopic examination or submitted slides. Fluid should not be submitted for cytology. Air-dried slides should be prepared by the veterinarian at time of collection. Dilute aspirates should first be concentrated by gentle centrifugation or gravity.
If culture of aspirate fluid is desired, immediately swab the fluid and place the swab into transport medium.

Glass Tubes or Jars Are NOT RECOMMENDED For Samples

If you are compelled to send glass, it must be protected by crushproof packaging. Crushproof, means you could step on the packaging and the glass would remain intact.
Postal and air express shippers employ highly automated systems, subjecting packaging to severe stresses. The very important sample in glass should be treated like you are shipping champagne glasses!!