Impact of preheparinization and sample volume on routine hematology findings in healthy cats

It can be challenging to collect sufficient blood from feline patients for both a biochemical profile and a complete blood count (CBC). The ability to generate accurate hematologic and biochemical data from a single, small (<2 ml) sample could reduce patient stress and improve clinical efficiency. The objective of this study was to determine the impact of preheparinization and/or sample size on routine hematology findings in cats.

Blood was collected from 20 healthy cats; measured aliquots were placed directly into tubes containing either EDTA or lithium-heparin (Hep). Within 2 mins, specific volumes were removed from the Hep tubes and placed in additional EDTA tubes. Four distinct sample sizes/types were created from each cat: (1) 1.3 ml EDTA (criterion standard); (2) 0.5 ml EDTA; (3) 1.3 ml Hep + EDTA; and (4) 0.5 ml Hep + EDTA. Three CBCs were performed on each sample using an automated bench-top hematology analyzer. Drops of blood were contemporaneously used to create three air-dried stained slides from each tube. Triplicate results were averaged for statistical analysis; results were compared across all sample types and against the criterion standard. Significance was set at P <0.05.

Preheparinization did not significantly impact determinations of erythrocyte number, hematocrit, hemoglobin concentration, mean cell volume and neutrophil count. Platelet counts for the non-traditional samples correlated poorly with the criterion standard, although numbers could be effectively estimated using stained slides. Cell morphology was well preserved across all sample types.

These results indicate that a 0.5 ml preheparinized EDTA blood sample can generate clinically useful hematologic data (excluding platelet count) in cats, using a bench-top analyzer. Our findings support the collection of a single small (<2 ml) sample that can be used for both biochemical and hematologic analyses. Further studies are needed to verify these findings using other hematology machines and in diseased cats.