APCR in FXa generation assays. (A) Effects of FV levels on the APCsr in the FV_Nara plasma. Normal plasma (open circles) and the patient’s plasma (closed circles) were mixed with FV-deficient plasma in various proportions, and FXa generation was measured with COATEST SP FVIII after the simultaneous addition of APC (40 nM) as described in “Materials and methods.” The APCsrs were expressed as ratios of the amount of generated FXa in the absence of APC divided by that in its presence. All experiments were performed at least 3 separate times, and the average values are shown. (B) APCR of FV-deficient plasma mixed with recombinant FV-W1920R. Various concentrations of FV (WT, open circles; W1920R, closed circles; R506Q, open squares) were mixed with diluted FV-deficient plasma, and FXa generation was measured with COATEST SP FVIII after the simultaneous addition of APC (40 nM), as described in “Materials and methods.” The APCsrs were expressed as ratios of the amount of generated FXa in the absence of APC divided by that in its presence. All experiments were performed at least 3 separate times, and the average and/or standard deviation values are shown.