Inhibitor development in previously untreated patients with severe haemophilia: A comparison of included patients and outcomes between a clinical study and a registry-based study.

In the registry-based study, patient numbers and completeness of follow-up were higher. The risk of developing an inhibitor to a single product was comparable. Although the sample size of this study was too small to conclude on differences in high- or low-titre inhibitors, this suggests that a registry could serve as a more suitable source for evaluation of high-titre inhibitors in the setting of factor VIII deficiency.