Disse inhibitorer er uden undtagelse IgG immunoglobuliner rettet mod faktor VIII’ s prokoagulante aktivitet som kvantificeres i Modificerede Bethesda Enheder (BE) pr. ml plasma. ###>These inhibitors are invariably IgG immunoglobulins directed against the factor VIII procoagulant activity, which are quantified in Modified Bethesda Units (BU) per ml of plasma.