Descriptive analysis of bleeding symptoms in haemophilia carriers enrolled in the ATHNdataset

Several studies have reported that haemophilia carriers have a bleeding tendency independent of factor activity. However, investigations have been fraught with methodological concerns. The ATHNdataset houses the largest data set of haemophilia carriers in the world. We undertook an analysis of haemophilia carriers in this data set using methodologies that characterize bleeding symptoms in carriers.

Determine the proportion of haemophilia carriers who have a normal bleeding score (BLS) and factors that affect the BLS.

The ATHNdataset was queried for haemophilia carriers with a documented BLS. Collected data included demographics, ISTH-BAT score, factor activity level, type of haemophilia (A or B), genotype and geographic residence.

Nine hundred twenty-two haemophilia carriers in the ATHNdataset reported a BLS. When adjusted for age, 74% reported a normal score. Logistic regression identified age, factor activity level, ethnicity and region of residence as risk factors for an abnormal score.

The majority of haemophilia carriers (74%) in the ATHNdataset had a normal BLS, including the majority (59%) with factor activity levels < 40 IU/dl. Conversely, 24% of haemophilia carriers with a factor activity level $$ 40 IU/dl reported an abnormal BLS. These results are consistent with previous studies of haemophilia carriers. Additional investigation is needed to determine why a majority of haemophilia carriers with low factor activity levels report normal BLSs while a significant minority of haemophilia carriers with normal activity levels report abnormal BLSs.