Comparison of platelet clumping and complete blood count results with Sysmex XT-2000iV in feline blood sampled on EDTA or EDTA plus CTAD (citrate, theophylline, adenosine and dipyridamole)

False thrombocytopenia may result from platelet aggregation, especially in feline ethylenediamine tetra-acetic acid (EDTA) blood specimens. Citrate, theophylline, adenosine and dipyridamole (CTAD) was added to 46 feline EDTA specimens to test its anti-aggregation action. Platelet aggregation was estimated from blood films and a complete blood count was performed with a Sysmex XT-2000iV analyser. Platelet aggregation score was >2 in 11/46 EDTA tubes and only in one EDTA + CTAD specimen. The platelet count was higher in all CTAD-supplemented tubes except one, medians measured by cytometry being 225.5 × 109/l and 249.0 × 109/l in EDTA and EDTA + CTAD, respectively (P = 0.007). Adding CTAD had statistically and analytically significant but moderate effects on other blood variables, the most intense variations being observed for reticulocytes (about 3% higher in EDTA specimens) and reticulocyte indexes. Addition of CTAD to EDTA when sampling feline blood is a useful option to reduce platelet clumping.