Evaluation of Collagen-Induced Platelet Aggregation Level Score Using an Automated Coagulation Analyzer

Light-transmission aggregometry is the gold standard for assessing platelet function. The scoring system, designed based on the results obtained using two different concentrations of agonists on semi-automated analyzers, is commonly used to confirm the effects of antiplatelet drugs in Japan. Given the time-intensive and laborious nature of LTA, along with the lack of standardization across laboratories and devices, automated and consistent methods to monitor platelet function are imperative. Recently, we developed a new parameter and equipped an automated coagulation analyzer with it. In this study, a new parameter, "collagen-induced platelet aggregation level (CPAL)," was developed, and its basic performance was evaluated and compared with the maximum aggregation rate of 1.0 mM arachidonic acid (AA-MA) and the result of the VerifyNow aspirin assay, ex-pressed in aspirin reaction units (ARU), performed on patients on antiplatelet therapy.

An automated coagulation analyzer was equipped with CPAL. CPAL is calculated as a score from 0.0 to 10.0 based on platelet aggregation patterns with 1.0 and 5.0 µg/mL collagen. Within-run precision was calculated by conducting five replicate analyses of the platelet-rich plasma (PRP) from healthy volunteers and 1.0 mM aspirin-spiked PRP. The dose-response effect of aspirin was evaluated using several concentrations of aspirin and PRP obtained from healthy volunteers. A comparative study was conducted using 62 PRP samples obtained from patients receiving antiplatelet therapy.

The coefficient of variation in within-run precision was within 5% for CPAL. Aspirin treatment affected CPAL expression in a concentration-dependent manner. A significant correlation was observed between CPAL and AA-MA (r = 0.70, p < 0.001). However, a very weak or no correlation was observed between CPAL and ARU (r = 0.17, p = 0.179).

CPAL exhibits acceptable performance. It showed good correlation with AA-MA but not with the ARU of VerifyNow, which changed with slight differences in aspirin concentration. CPAL is a new platelet aggregation scoring system that may be used to monitor the effects of aspirin using an automated coagulation analyzer.