Risk factors for coagulation inhibitor development in children with severe hemophilia A

Aim of the study: to examine the role of potential risk factors in inhibitor development in previously untreated patients (PUPs) (or minimally treated patients) with severe hemophilia A. The study was approved by the Independent Ethics Committee and the Scientific Council of the Belarusian Research Center for Pediatric Oncology, Hematology and Immunology (the Republic of Belarus). The study included 89 boys who underwent regular follow-up for severe hemophilia A at the Belarusian Research Center for Pediatric Oncology, Hematology and Immunology (the Republic of Belarus) from 1998 to 2022. The median age (10th–90th percentile) at diagnosis of hemophilia was 8.0 (1.0–21.0) months, the baseline factor VIII activity was 0.7% (0.4–0.95%). Age at first exposure to factor VIII concentrate was 11.0 (1.0–31.0) months. Out of 89 patients, 23 children had severe hemophilia A with inhibitors. The cumulative incidence of inhibitors in the whole group of PUPs was 31.0 ± 5.6%. The cumulative incidence of hemophilia A with inhibitors was higher in the patients with null mutations (37.0 ± 6.9%) than in the patients with non-null mutations (6.5 ± 6.0%) (the log-rank test, p = 0.041). The use of plasma-derived FVIII concentrate (approved for use in neonates and for prophylaxis) from one manufacturer was associated (c2 = 8.53; p = 0.004) with a lower incidence of factor VIII inhibitors (up to 21.3 ± 8.5%) compared with the incidence in the group of patients treated with FVIII concentrates from different manufacturers (45.2 ± 7.8%). Age ( 1 year old or 1 year old) at first exposure to FVIII had no effect on the formation of inhibitors (the log-rank test, p = 0.746). Such factors as age at diagnosis of hemophilia (odds ratio (OR) 0.99; 95% confidence interval (CI) 0.93–1.024; p = 0.991) and baseline factor VIII activity (OR 0.99; 95% CI 0.8–1.06; p = 0.09) were not associated with inhibitor development. The first measurements of activated partial thromboplastin time (APTT) ratio (patient APTT value over the APTT reference value) (OR 1.89; 95% CI 0.72–5.09; p = 0.21) and FVIII recovery in vivo (OR 0.74; 95% CI 0.27–2.01; p = 0.55) were not associated with inhibitor development either. We have confirmed that one of the main risk factors for FVIII inhibitor development is F8 gene mutations. The incidence of inhibitors among the patients who received plasma-derived FVIII concentrates (recommended for use in PUPs in the neonatal period) from one manufacturer was lower than among those who received FVIII from different manufacturers.