Influence of test time on results of the impedance aggregometer Multiplate® analyser in dogs

The Multiplate® analyser is a relatively new impedance aggregometer designed for human medicine but was recently evaluated for canine blood. The aim of this study was to determine the influence of test time (i.e. measuring period) on reference values and the validity of measurement results in canine blood. Based on blood samples of 83 healthy dogs, reference values for different test times (6, 8, 10 and 12 min) were established for area under the curve (AUC) and maximum aggregation values for adenosine diphosphate (ADP)-, collagen- and arachidonic acid-induced aggregation. The results of 134 samples of 117 dogs with various diseases and eight samples with reduced platelet function owing to treatment with the platelet aggregation inhibitor clopidogrel were calculated for different test times and classified as decreased, normal or increased. Maximum aggregation and AUC values increased significantly with increasing test time. Chi square test did not show significant differences between the various test times with regard to the number of increased and decreased measurement results for any agonist. All samples of dogs treated with clopidogrel and measured with the agonist ADP revealed decreased AUC values at any time point. The results of our study indicate that test time significantly influences AUC and maximum aggregation values but has limited influence on sensitivity of measurement results of canine blood using the investigated instrument.