Influence of plasma coagulation proteins on the pSR. pSRs were plotted as a function of the concentration of prothrombin (▴), factor V (•), factor VII (○), factor VIII (▾), factor IX (▿), factor X (▪), or antithrombin (□). Coagulation factor–depleted plasmas were mixed with normal pooled plasma. Each data point represents the mean ± SD of at least 3 measurements. Purified human prothrombin was added to normal pooled plasma to obtain plasma with 133% prothrombin.