Inhibitors increase the burden of disease in nonsevere haemophilia A patients - treatment strategies to obtain hemostasis

Introduction and Objectives: Neutralizing antibodies (inhibitors) directed against the FVIII protein may increase the bleeding frequency and compromise the management of bleeding episodes in nonsevere haemophilia A patients. The median annual bleeding frequency in patients without inhibitors is described to be 0 (IQR 0-3) for mild haemophilia and 1 (IQR 0-13) for moderate haemophilia. The aim of this study was to evaluate the burden of bleeding and to describe the treatment strategies that are used for bleeding episodes in a large group of unselected inhibitor patients with nonsevere haemophilia A. Materials and Methods: We included all inhibitor patients from the INSIGHT study, an international multicentre cohort study including all 2709 nonsevere HA patients (FVIII:C 2-4 IU/dL) that received at least 1 exposure to FVIII concentrate between 1980-2011. Data of the 1st inhibitor period were analyzed. Results: We included 107 nonsevere HA inhibitor patients (median baseline FVIII:C 9 IU/dL (IQR 6-16); median age of 38 years (IQR 15-61)). A high titre inhibitor (> 5 BU/mL) was present in 57 (53%) patients. In 30 (28%) patients the FVIII:C level was decreased ≤1 IU/dL. Eighty-nine patients (83%) received treatment for bleeding episodes. Most patients had spontaneous bleeds (n = 49, 46%); a higher proportion of high titre patients had spontaneous bleeds compared to low titre patients (83% vs. 53%, relative risk (RR) 2.7, 95% confidence interval (CI) 1.3-5.8). The median number of bleeding episodes per inhibitor year was 2 (IQR 1-5); this did not differ between patients with FVIII:C ≤ 1 IU/dL and those with measurable FVIII levels (p = 0.5), patients with low titre and high titre inhibitors (p = 0.5) and patients receiving eradication treatment or not (p = 0.7). In order to treat bleedings, FVIII concentrate was used in 59 patients (55%), FVIII bypassing agents in 50 (47%) and desmopressin in 18 patients (17%). Desmopressin was used more often in patients with remaining circulating FVIII:C levels compared to patients with a FVIII:C ≤ 1 IU/dL and in patients without eradication treatment compared to patients with eradication treatment (25% vs. 3%; RR 7.4, CI 1.0-53.5 and 25% vs. 0%; RR 14.0, CI 0.9 - 224.6, respectively). Conclusion: Inhibitor development in nonsevere HA patients aggravates the burden of bleeding with the majority (83%) of the patients needing treatment for bleeding episodes, at a median of 2 bleeding episodes per year.