Feline platelet counting with prostaglandin E1 on the Sysmex XT‐2000iV

Background: The large size of many feline platelets and the high frequency of platelet aggregation often results in falsely low platelet counts in this species. A combination of optical platelet counting to detect even large platelets and the use of prostaglandin E1 (PGE1) to inhibit platelet clumping may increase the accuracy of feline platelet counting. Objective: The objective of this study was to compare platelet counts in feline whole blood samples with and without the addition of PGE1 and using different analytical methods in a clinical setting. Methods: Platelet counts were determined in 10 feline patients in a referral veterinary hospital using 2 sample types (EDTA, EDTA with PGE1) and 2 methods of analysis (optical counting PLT‐O] and impedance counting PLT‐I]) on the Sysmex XT 2000 iV analyzer. Results: All PGE1–PLT‐O samples had platelet counts of >200 × 10⁹/L. Mean platelet count using PGE1–PLT‐O (410,256±178 × 10⁹/L) was significantly higher (P<.03) compared with PGE1–PLT‐I (256±113 × 10⁹/L), EDTA–PLT‐O (238±107 × 10⁹/L), and EDTA–PLT‐I (142±84 × 10⁹/L) methods. Depending on the method, platelet counts in 2 to 7 of 10 cats were <200 × 10⁹/L when PGE1‐PLT‐O was not used. A slightly increased platelet count in response to treatment of a feline patient with thrombocytopenia would have been missed without use of PGE1–PLT‐O. Conclusions: Using PLT‐O analysis on EDTA samples containing PGE1 provides higher, and therefore likely more accurate, feline platelet counts in a clinical setting.