Correlation between FVIII activities measured in OS and CS assays. FVIII activity data from OS and CS assays in BMN 270 clinical trials 270-201 (A), 270-301 (B), and in 20 healthy donors (C) were correlated using linear regression. Each data point represents FVIII activity data from 1 visit; multiple visits for the same participant are represented by the same colored symbol. The slope of the regression curve reflects the constant rate of change between the OS and CS activity measurements.