Impact of Early Factor VIII Exposure, Prophylaxis and Prenatal/Perinatal Events on Inhibitor Risk in Children with Hemophilia A: A Case-Control Study.

In a multicenter case-control study we investigated the impact of prenatal/perinatal events and early FVIII exposure on the inhibitor risk in hemophiliacs. Patients: 102 children (age:13–196 months) with hemophilia A (FVIII≤2%) exclusively treated with recombinant FVIII and evaluated for inhibitors every 3 months were included. Forty-seven patients who developed inhibitors at the median age of 26 months (4–80) after a median of 16 exposure days (ED, 5–150), 37 high-responders (6–500 BU/mL) and 10 low-responders (<5 BU/mL), were compared with 55 children who did not develop inhibitors after at least 20 ED (5<50, 4<100, 10<200 and 36>200 ED). Results: by univariate analysis, family history of inhibitors, intron 22 inversion and prophylaxis started after the first 20 ED were significantly associated with an increased risk of inhibitor development (OR 9.5, 95%CI 1.1–79.9; OR 2.7, 95%CI 1.1–6.6; OR 3.7, 95%CI 1.1–12.1, respectively). No statistically significant differences were found for variables such as villocentesis/amniocentesis, premature/caesarian birth, breast-feeding, surgery, central venous devices and FVIII infusions associated with infections/vaccinations. By multivariate analysis, the inhibitor risk was 2.8-folds (95%CI 1.1–7.3) in children with intron 22 inversion and 4.5-folds (95%CI 1.1–17.5) in patients who started prophylaxis after the first 20 ED. By univariate and multivariate analysis, there was not a linear trend in the inhibitor development according to the age at first FVIII exposure (≤6, 7–12, 13–18, 19–24, >24 months). Conclusions: this study showed that starting prophylaxis within the first 20 ED had a favourable impact on the inhibitor risk independently from the age at first FVIII exposure.