Prevalent inhibitors in haemophilia B subjects enrolled in the Universal Data Collection database

Abstract

Several risk factors for inhibitors have recently been described for haemophilia A. It has been assumed that similar risk factors are also relevant for haemophilia B, but there is limited data to confirm this notion. The aim of this study was to determine the prevalence of and risk factors associated with inhibitors in haemophilia B. The database of the Universal Data Collection (UDC) project of the Centers for Disease Control for the years 1998-2011 was queried to determine the prevalence of inhibitors in haemophilia B subjects. In addition, disease severity, race/ethnicity, age, factor exposure and prophylaxis usage were evaluated to determine their impact on inhibitor prevalence. Of the 3785 male subjects with haemophilia B enrolled in the UDC database, 75 (2%) were determined to have an inhibitor at some point during the study period. Severe disease (OR 13.1, 95% CI 6.2-27.7), black race (OR 2.2, 95% CI 1.2-4.1), and age <11 years (OR 2.5, 95% CI 1.5-4.0) were found to be significantly associated with having an inhibitor. There was insufficient data to determine if type of factor used and prophylaxis were associated with inhibitors. Inhibitors in haemophilia B are much less prevalent than haemophilia A, especially in patients with mild disease. Similar factors associated with inhibitors in haemophilia A also seem to be present for haemophilia B. The information collected by this large surveillance project did not permit evaluation of potential risk factors related to treatment approaches and exposures, and additional studies will be required.

Keywords: Universal Data Collection; factor IX; haemophilia B; inhibitors; prevalence; race.

Figure 1

Identification of Hemophilia B Inhibitor Patients in the UDC Database Reveals how inhibitor subjects were identified. The initial screen of the database revealed 203 potential subjects with an inhibitor based on a titer of 0.5 Bu ml⁻¹ or greater. Of these 128 were shown not to have an inhibitor based on PI response to inquiries of their submitted data or UDC data alone for those subjects whose PI did not respond to inquiries. This left 75 subjects with an inhibitor. ITI= immune tolerance induction therapy; Bypass= use of a bypassing agent such as recombinant factor VIIa or an activate prothrombin complex concentrate