This survey provides new information on the severity of factor IX deficiencies among patients being treated for haemophilia B and on the prevalence of factor IX inhibitors in this population. A questionnaire was sent to 150 haemophilia treatment centres in the United States and Canada. 82 centres responded and provided data on 1967 patients with haemophilia B. 37% of these patients had severe haemophilia B (< 1% of the normal level of factor IX), 33% had moderate haemophilia B (1-5% of the normal level of factor IX), and 30% had mild haemophilia B (> 5% of the normal level of factor IX). Only 29 (1.5%) of the patients had factor IX inhibitors; 28 of these patients (96.6%) had severe haemophilia B, and one of these patients (3.4%) had moderate haemophilia B. Factor IX inhibitor titres were 0.6-1 Bethesda unit (BU) in seven patients, > 1-5 BU in four patients, > 5-10 BU in one patient, and > 10 BU in 17 patients. Factor IX inhibitors are much less common in patients with haemophilia B than in patients with haemophilia A.
CITATION STYLE
Katz, J. (1996). Prevalence of factor IX inhibitors among patients with haemophilia B: Results of a large-scale North American survey. Haemophilia, 2(1), 28–31. https://doi.org/10.1111/j.1365-2516.1996.tb00006.x
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