Race and ethnicity and the success of immune tolerance induction among people with severe haemophilia A in the United States

Introduction: Immune tolerance induction (ITI) is the only treatment to eradicate inhibitors in people with severe haemophilia A with inhibitors. Since the risk of inhibitor development is greater among Black and Hispanic persons, it has been hypothesized that race and ethnicity may influence ITI success. Limited studies have evaluated this hypothesis. Aim: To examine the success of ITI according to race and ethnicity. Methods: Participants who entered the Community Counts (CC) Registry between 2013 and 2017, were aged >= 3 years at study entry, and received ITI were included (n = 559). The proportion of participants with successful ITI was examined with adjusted prevalence ratios (aPRs) and corresponding 95% confidence intervals (95% CIs). Results: Among 559 participants, 56.9%, 19.1%, 18.1% and 4.3% were Non-Hispanic (NH) White, NH Black, Hispanic and Asian, respectively, and 1.7% were coded as other or missing. Approximately 80% of Hispanic, NH Black and NH White participants had good/very good prognosis, defined as having a pre-ITI peak inhibitor of < 200 Bethesda Units per millilitre. Nearly 60% of participants (59.7%) achieved successful ITI, 20.7% and 19.5% experienced partially successful or failed ITI, respectively. Successful ITI was non-significantly lower in NH Black (54.2%; aPR = 0.95, 95% CI 0.62-1.44) and Hispanic (55.4%; aPR = 0.89, 95% CI 0.71-1.13) relative to NH White participants (62.6%). Conclusion: In this study, 60% of participants in the CC Registry had successful ITI, consistent with previous studies. The proportion with successful ITI was generally comparable across racial and ethnic groups with similar prognosis. These findings do not support the hypothesis that ITI response varies according to race or ethnicity.