Validation of storage and shipping of feline blood samples for analysis on the Platelet Function Analyzer‐200 for determining the effect of clopidogrel

BACKGROUND: The Platelet function analyzer-200 (PFA-200) can determine the effect of clopidogrel in cats, but analysis traditionally must be performed at point-of-care (POC). The ability to ship samples of blood to a laboratory would allow widespread access. OBJECTIVES: We aimed to validate the shipping of blood samples for PFA-200 analysis in cats to determine the effect of clopidogrel. METHODS: Twenty healthy cats and 10 cats receiving clopidogrel were recruited. Blood was collected from cats and aliquoted into two samples, one was analyzed at POC within 2 hours using the PFA-200, and the other was packaged and transported to a location 4 km away, stored, and transported back to the lab for analysis the following day. RESULTS: Median closure times (CTs) with the collagen/adenosine diphosphate (COL/ADP) cartridge in healthy cats were 51.5 seconds (POC) and 78.8 seconds (shipped), which were significantly different (P < 0.001), and for cats on clopidogrel, median CTs were 147.5 seconds (POC) and 190 seconds (shipped), which were not significantly different (P = 0.131). Median CTs with the P2Y cartridge in healthy cats were 50.5 seconds (POC) and 64.9 seconds (shipped), which were significantly different (P = 0.03), and in cats receiving clopidogrel, median CTs were 300 seconds (POC) and 300 seconds (shipped) which were not significantly different (P = 1.000). Reference intervals for CTs differed for COL/ADP at POC (19.8-89.7 seconds) and shipped (50.9-161.6 seconds) and for P2Y at POC (35.5-118.8 seconds) and shipped (35.1-108.9 seconds). Receiver operating characteristics showed similar areas under the curve (AUCROCs) regarding the effect of clopidogrel for COL/ADP at POC (0.994 seconds) and shipped (0.932) and for P2Y at POC (0.904 seconds) and shipped (0.975 seconds). When classifying for the presence of clopidogrel effects, Cohen's Kappa was 0.62 for COL/ADP and 1.00 for P2Y. CONCLUSIONS: Shipping blood samples for PFA analysis are feasible with similar performance to POC analyses for determining the effect of clopidogrel in cats.