Diagnosis and Management of Acquired Hemophilia A

Diagnostic Criteria

Prolonged aPTT with failed mixing study correction is a hallmark finding that distinguishes acquired hemophilia A from congenital hemophilia, indicating the presence of an inhibitor rather than a factor deficiency, as stated by the European Hematology Association 1, 2
The mixing test failure indicates an inhibitory substance (autoantibody) rather than simple factor deficiency, as factor deficiencies would correct when mixed with normal plasma, according to the International Society on Thrombosis and Haemostasis 3, 4
Normal platelet count and normal PT exclude platelet disorders and extrinsic pathway defects, as noted by the American Society of Hematology 5

Factor VIII activity level measurement will be reduced in acquired hemophilia A, as recommended by the British Committee for Standards in Haematology 7, 3, 6
Bethesda assay to quantify the factor VIII inhibitor titer, though it may underestimate autoantibody potency due to type 2 kinetics, as stated by the European Hematology Association 2, 3
Factor VIII antibody ELISA if results are ambiguous or to distinguish from lupus anticoagulant, as suggested by the International Society on Thrombosis and Haemostasis 4
Lupus anticoagulant testing to exclude this alternative cause of non-correcting mixing studies, as recommended by the American College of Rheumatology 3, 4, 6

Immediate hemostatic control is the priority using bypassing agents (recombinant activated factor VII or activated prothrombin complex concentrate), as stated by the European Hematology Association 2, 8
Immunosuppressive therapy should be initiated immediately upon diagnosis to eradicate autoantibodies, as recommended by the International Society on Thrombosis and Haemostasis 2, 8, 4