Correlation between titers of FVIII-specific IgG4 and titers of FVIII-specific IgG1 in hemophilia A patients with inhibitors (HA-INH). The correlation between titers of FVIII-specific IgG4 and titers of FVIII-specific IgG1 in hemophilia A patients with inhibitors was determined using the 2-tailed nonparametric correlation according to Spearman, and calculated using GraphPad Prism 5 software. The correlation coefficient (r) and the 95% confidence intervals (in parentheses) are indicated. The correlation is significant (*P ≤ .05).