Handling and Transportation of Samples
Samples for complete blood cell counts (CBCs) should be submitted in ethylenediaminetetraacetic acid (EDTA) tubes, filled to the proper amount indicated on the container, and inverted several times to ensure proper mixing of the blood with the anticoagulant.
Too little blood may result in a falsely decreased packed cell volume (PCV) caused by shrinkage of red blood cells (RBCs). When collecting for both a CBC and serum biochemical profile, blood should first be put in an EDTA tube and then in a serum tube that does not contain anticoagulant. Care must be taken to avoid contaminating the blood remaining in the syringe with retrograde flow of EDTA blood because this can alter calcium and potassium values on the serum biochemistry.1 Samples for coagulation testing (prothrombin time and activated partial thromboplastin time) should be placed in a sodium citrate tube at a proportion of 1:9 with blood. Concurrently sending blood from a clinically healthy animal can serve as a control to help assess artifacts if there is a delay in sample transit. Samples for plasma fibrinogen concentration can be submitted as whole blood in either EDTA tubes or in sodium citrate tubes.3 Consultation with the reference laboratory is advised because the technique used by a specific laboratory will dictate how the sample should be submitted.Blood smears for microscopic evaluation should be made immediately to minimize artifacts from deterioration of cells. Blood smears should also routinely be made for manual differential counting, to check for platelet clumps that may be artificially decreasing the platelet count and to evaluate for hemoparasites and atypical cells that would otherwise not be detected. Hematologic results are affected by the ambient storage temperature and the time interval between collection and evaluation. If samples cannot be run immediately on a hematology analyzer, they should be refrigerated. In cattle and goats, if blood samples are handled appropriately, hemoglobin concentration, RBC count, and total white blood cell (WBC) count are stable for the first 24 hours after collection. PCV is stable for up to 12 hours with mild increases at 24 hours.4 Blood should not be frozen because this will rupture the cells.1 Shipping and packaging of samples for hematologic and cytologic evaluation should follow guidelines from the reference laboratory.