Fig. 4. Linear regression analysis of the transfusion rate with the use of aprotinin or tranexamic acid according to the underlying transfusion rate. All studies included in the meta-analysis are represented by a circle . The size of each circle is proportional to the size of the trials. Event rates: proportion of patients transfused with allogeneic erythrocyte according to a transfusion protocol. The solid lines are calculated linear regressions weighted by the number of patients included in each study. The dashed lines are 95% confidence intervals of the regression lines. R 2is the coefficient of linear correlation; P is the probability that the slope of regression differs significantly from zero. The dotted lines represent equivalence. Studies below these dotted lines are in favor of the efficacy of the antifibrinolytic.