Approximately 15% of patients with hemophilia A develop inhibitors to Factor VIII. These inhibitors have a high degree of specificity for Factor VIII procoagulant activity. Inhibitor patients seem to fall into 2 groups: roughly 3/4 are “strong” responders, whose Factor VIII antibody titer rises substantially after exposure to Factor VIII, while the remainder are “weak” responders, whose antibody level remains below 3-5 Bethesda units/ml despite exposure to Factor VIII. The latter group can be treated successfully with Factor VIII, although the dose required may be greater than in non-inhibitor patients. The “strong” responders can be treated with Factor VIII if their antibody titer is very low, although anamnesis will ensue within 3-4 days, reaching a maximum in 10-20 days. When antibody titers are high, treatment can be extremely difficult. Use of Factor VIII may still be possible, when combined with massive plasmapheresis; otherwise treatment with vitamin K-dependent factor concentrates may be attempted. A variety of such concentrates is available, both “non-activated” and “activated”. The former type of product may have become less useful for the treatment of inhibitor patients in recent years. The NTH Cooperative Study of Factor VIII Inhibitors in Hemophilia A has recently conducted a double-blind study of Konyne and Proplex in the treatment of Inhibitor patients. These results will be presented.
Autoplex versus proplex: a controlled, double-blind study of effectiveness in acute hemarthroses in hemophiliacs with inhibitors to factor VIII
