Inhibitor incidence after intensive FVIII replacement for surgery in mild and moderate haemophilia A: a prospective national study in the Netherlands

Summary Inhibitor development is currently the most severe complication in mild/moderate haemophilia A patients, causing increased bleeding tendency, hospitalization and mortality. It has been suggested that receiving high doses of factor VIII (FVIII) concentrates for surgical procedures is an important risk factor for inhibitor development in these patients. The current multicentre study aimed to determine prospectively the incidence of inhibitor development after intensive FVIII replacement therapy for surgical procedures in patients with mild/moderate haemophilia A. All consecutive patients with mild/moderate haemophilia A were included when they required at least 10 000 iu of FVIII concentrates (or 250 iu/kg) for 5 or more days for a surgical procedure. Potential clinical risk factors for inhibitor development and results of inhibitor tests were collected. Forty‐six patients with a median age of 54 years (interquartile range, 40–59 years) were included in the study. F8 genotyping revealed 20 different missense mutations. Patients received either recombinant (65%) or plasma‐derived FVIII concentrates (35%) by intermittent bolus injections (41%) or continuous infusion (57%). Two patients developed a low titre inhibitor post‐operatively. The incidence of inhibitor development following intensive treatment for surgery in this unselected prospective cohort of mild/moderate haemophilia A patients was 4% (95% confidence interval, 0·5–14·8).