Flow cytometric parameters for characterizing platelet activation by measuring P-selectin (CD62) expression: Theoretical consideration and evaluationin thrombin-treated platelet populations

Two flow cytometric parameters are generally used to quantify platelet acti vation as measured by P-selectin (CD62) expression: percentage and mean cha nnel fluorescence of CD62-positive platelets (%(+) and MCF+, respectively). We describe a method for calculation of indices of platelet activation for positive (IPA(+)) and total (IPA(Sigma)) platelets, which reflect integrat ed amounts of CD62 expressed in these populations; IPA(+) is calculated as the product of %(+) and MCF+, whereas IPA(Sigma) is exclusively determined by mean fluorescence of the total platelet population (MCFSigma) and does n ot depend on %(+). We use these parameters to characterize human platelet a ctivation in whole blood samples treated with varying human alpha-thrombin concentrations, mimicking the variations in platelet activation in a number of clinical settings. Multiparameter analysis of CD62 expression may be us eful for selective diagnosis of disorders with systemic or localized platel et activation and for monitoring the clinical course of the disease and eff ect of therapeutic interventions. (C) 2000 Academic Press.