Measurement of coagulation factor antibody levels is useful for diagnosis and determining therapeutic efficacy in hemorrhagic patients with autoantibodies to coagulation factor VIII and factor V: results from a single center in Japan.

Coagulation factor inhibitors (CFIs) sometimes cause fatal bleeding conditions. Determination of an inhibitor titer (INH-titer) using the Bethesda method is essential for diagnosing diseases associated with CFIs and examining the effects of immunosuppressive therapy. We reviewed 17 cases with CFIs (acquired hemophilia A, n = 11; FV inhibitor, n = 6) to examine the usefulness of determining quantities of an autoantibody to a coagulation factor (CF-IgG) by ELISA for diagnosis and therapeutic efficacy, as compared with INH-titer. One patient with an INH-titer and no evidence of CF-IgG was lupus anticoagulant (LA)-positive, and thus the positive INH-titer may have been a false positive caused by LA. Although INH-titer alone was insufficient to correctly identify patients with CFI, determination of CF-IgG appeared to be useful. In addition, even after INH-titer disappearance, hemorrhagic conditions recurred when CF-IgG was detected. These findings suggest that the presence of a clearance antibody against the coagulation factor might reduce the activity of that coagulation factor even after disappearance of the corresponding neutralizing antibody. Although the diagnosis and therapeutic efficacy can also be determined by INH-titer disappearance and improvement of corresponding coagulation factor activity, determination of CF-IgG by ELISA can improve the accuracy of these assessments.