ACQUIRED HEMOPHILIA-A - ERRORS IN THE DIAGNOSIS

The distinction between a specific factor inactivator and a non-specif ic inhibitor is important when confronted by a patient with a history of bleeding and abnormal in-vitro coagulation tests. We report on two patients who presented with bleeding and a prolonged activated partial thromboplastin time. Initial factor assays suggested combined deficie ncy of factors VIII and IX as a result of the presence of inactivators . The use of dilution studies, chromogenic assays, a novel in-house en zyme-linked-immunosorbent-assay-based technique and phospholipid neutr alization, demonstrated that Case 1 had a genuine factor VIII inactiva tor resulting in factor VIII levels of less than 1 IU/dl but no factor IX deficiency. Case 2 had normal levels of factor VIII on further tes ting and no specific inactivator to either factor VIII or IX but a pot ent antiphospholipid antibody which had interfered with the phospholip id-dependent in-vitro assays. Care must be taken in the interpretation of laboratory assays in the presence of antiphospholipid antibodies t o ensure that the correct diagnosis is made and inappropriate treatmen t avoided. (C) 1998 Lippincott Williams & Wilkins.