Effect of age, sex, breed and venipuncture site on platelet count and clumping in feline blood samples

Objectives To evaluate the associations between sex, age, breed and collection site on platelet count and platelet clumping in feline blood samples.Methods Cats presenting to a primary care feline hospital from January 2016 to January 2017 were recruited. Any cat undergoing blood collection for a complete blood count was eligible. Cats were excluded if they were receiving clopidogrel or aspirin, had a disease known to affect platelet function, or if they required sedation for phlebotomy. All cats had their sex, age, site of venipuncture, platelet count, degree of platelet clumping and platelet morphology recorded.Results In total, 649 cats were prospectively recruited. Of these, 579 (89%) cats had no clumping observed on blood smears. A significant association (P = 0.025) was found between sex and platelet count, with females having lower platelet counts. No significant association was found between sex and degree of platelet clumping (P = 0.323). Age did not have a statistically significant association with platelet clumping (P = 0.959); however, it did have a small significant (P = 0.003) positive correlation with platelet count. There was no significant effect of purebred status on platelet count (P = 0.457); however, the domestic group had a higher rate of platelet clumping (P = 0.009). No association was found between platelet count (P = 0.322) or degree of platelet clumping (P = 0.793) and collection site. When considering platelet clumping as a binary outcome, no association was found with sex (P = 0.292), age (P = 0.681), site of collection (P = 0.809) or breed (P = 0.264).Conclusions and relevance The lack of effect of collection site/technique suggests that multiple sites of collection are valid when accurate platelet counts are important. The finding of lower platelet counts in younger and female cats may highlight the need to recognize age and sex when considering the management and monitoring of platelet counts and platelet disorders. Additional studies are needed to understand breed variation.