Effectiveness of factor VIII infusions in haemophilia A patients with high responding inhibitors.

We report here the efficacy of factor VIII (FVIII) infusions in two haemophiliacs with inhibitors using clot waveform analysis on the MDA II system, which was possible to detect very low levels of FVIII activity < 1.0 U dL(-1). In the presence of type 1 inhibitors at the level of 6.2 (patient 1) and 14.4 (patient 2) Bethesda Units mL(-1), 3.2 and 6.5 U dL(-1) of FVIII:C remained 30 min after the infusion of FVIII (100 U kg(-1)), respectively. Moreover, 0.9 U dL(-1) of FVIII:C remained 24 h after infusion in patient 2. In both cases, these changes were reflected by qualitative improvement in the aPTT clot waveform and quantitative changes in the minimum value of the second derivative of the aPTT waveform (Min2) that reflects clot acceleration. These results suggest that FVIII infusion may be continued with clinical benefit in some haemophiliacs with high responding inhibitors. Furthermore, the haemostatic response may be monitored accurately and efficiently by clot waveform analysis.