LAUSR

Inhibitor formation in non‐severe haemophilia A is a life‐long risk and associated with morbidity and mortality. There is a paucity of data to understand real‐world inhibitor screening practice. We evaluated the treatment burden, haemostatic strategies, F8 genotyping and inhibitor screening practices in non‐severe haemophilia A in seven London haemophilia centres. In the 2‐year study period, 44% (377/853) patients received at least one haemostatic treatment. Seventy‐nine percent of those treated (296/377) received factor VIII (FVIII) concentrate. F8 genotype was known in 88% (331/377) of individuals. Eighteen per cent (58/331) had ‘high‐risk’ F8 genotypes. In patients with ‘standard‐risk’ F8 genotypes treated on‐demand with FVIII concentrate, 51·3% episodes (243/474) were screened within 1 year. However, poor screening compliance was observed after ‘high‐risk’ treatment episodes. In patients with ‘standard‐risk’ F8 genotypes, 12·3% (28/227) of treatment episodes were screened in the subsequent 6 weeks after surgery or a bleed requiring ≥5 exposure days. Similarly, in the context of ‘high‐risk’ F8 genotypes after any FVIII exposure, only 13·6% (12/88) of episodes were screened within 6 weeks. Further study is required to assess optimal practice of inhibitor screening in non‐severe haemophilia A to inform subsequent clinical decisions and provide more robust prevalence data to further understand the underlying immunological mechanism.