Thrombin generation in 20210A carriers. Thrombin generation during clot lysis was determined in 10 prothrombin 20210A carriers (prothrombin activity, 130% ± 19.5%) and in 10 control donors (prothrombin activity, 95% ± 15.4%). Thrombin activity was measured by clotting assay on aliquots taken from the clot lysis mixture at the indicated intervals. Results are the mean ± SD. * indicates P < .05; †, P < .01. Times to peak were 5.9 and 4.5 minutes in 20210A carriers and control donors, respectively (P < .025).