Patterns of factor prophylaxis in the Canadian hemophilia A population

Abstract number: P1624

Blanchette^* P., Stain^* A. M., Rivard† R., Israels‡ S., Robinson§ S., Ali¶ K., Walker†† I., Blanchette^* V.

‡Cancer Care Manitoba, Canada; †Hôpital Ste-Justine, Canada; ††Hamilton Health Sciences, Canada ^*Hospital for Sick Children, Canada; §QEII Health Sciences, Canada; ¶Saskatoon Cancer Center, Canada;

High-dose factor prophylaxis [25–40 factor units (u) alternate days, minimum × 3/week] started at age 1–2 years of life in boys with severe hemophilia prevents the development of significant arthropathy. However, programs of prophylaxis are very expensive and venous access is a challenge. To ascertain patterns of prophylaxis, defined as the regular administration of factor VIII at least once weekly, in the Canadian hemophilia A population a survey was conducted. The response rate to the survey was 90%, and the survey identified 247 inhibitor-negative individuals on prophylaxis in 14 hemophilia treatment centers. Hemophilia was severe in 95% (235/247), and moderate in the remaining cases. The annual factor VIII use in the 247 individuals was 44.3 million units (all cases received recombinant factor VIII), representing 39% of factor VIII used in Canada in the one year period of this study. The mean factor VIII dose infusion was 28 U kg^-1 (median 26 U kg^-1, range 4–101 U kg^-1). The frequency of infusion was as follows:

High-dose factor prophylaxis, defined as infusion of factor VIII? × 3/week, was used most frequently in subjects <5 years of age (23/28 cases, 82%) as compared to 56% (56/100), 66% (40/61) and 62% (36/58) of subjects ages 5–12, 13–18 and >18 years. The mean infusion dose of factor VIII in these four age groups as follows: <5 years – 42.5; 5–12 years – 29.8; 13–18 years – 24.4; and > 18 years – 29.8 units kg^-1. These data are useful for planning the ongoing need for factor VIII and reflect a shifting emphasis on primary prophylaxis started at a young age in boys with severe hemophilia in order to prevent arthropathy.