Clinical evaluation of platelet function analyzer PFA-100 in dogs

The platelet-function-analyzer PFA-100 (Fa. Dade Behring, Liederbach) proofs the capillary in vitro bleeding time by the blood flow through a capillary. The membrane at the end of the capillary is a membrane with a layer of an inductor of the platelet aggregation (collagen/ADP or collagen/epinephrine). The closure time and optional the blood volume flowing out of the capillary can be determined. To find out the applicability of the analyzer for canine blood samples several examinations were carried out in this study. Eased on 45 blood samples of clinically healthy dogs a reference range (2.5%- and 97.5% quantile) was defined. Using the collagen/ADP test cartridge the reference range for the closure time was 47-81 s and for the blood volume 223-303 mu l. Using the collagen/epinephrine test cartridge the reference range for the closure time was 67-210 s and for the blood volume 269-611 mu l. In addition, blood samples (n = 19) of dogs with different degrees of thrombocytopenia were examined. Hereby, in contrast to the collagen/epinephrine cartridge, the collagen/ADP cartridge showed a high sensitivity regarding the closure time (n = 18) as well as the blood volume (n = 17). Regarding the results of the healthy dogs and dogs with thrombocytopenia a moderate close correlation was calculated between the in vitro bleeding time and the capillary in vivo bleeding time (r(s) = 0.590). After intravenous injection of 20 mg/kg acetylsalicylic acid the closure time measured with the collagen/ADP cartridge was 1.3fold prolonged. The reference range was not exceeded in every case; With artificial variation of the haematocrit a clear prolongation of the closure time at haematocrit values less than or equal to 25% was demonstrated. These results indicate that clinical usability of the platelet function analyzer in dogs is restricted despite its sensitivity to disorders of primary haemostasis.