The limitation of factor IX coagulant activity determination in the diagnosis of hemophilia B carriers.

A preliminary study of factor IX coagulant activity (FIX:C) for determining hemophilia B carriers was conducted at the Department of Pediatrics, Faculty of Medicine Ramathibodi Hospital in Bangkok. Twenty-eight females (8 obligate, 20 potential carriers) from 17 hemophilia B families were enrolled in the study. Additionally, 25 normal females were included. They were not pregnant and not using oral contraceptives. Then, three cut-off levels of FIX:C including 50 per cent which was the commonly used level; 57 per cent which was the mean-2 SD of normal females and 75 per cent which was the level reported by Knobe and Ljung in 1999 were used for the diagnosis of hemophilia B carriers. The sensitivities of these three cut-off levels were 12.5 per cent (1/8) for 50 per cent, 37.5 per cent (3/8) for 57 per cent and 50 per cent (4/8) for 75 per cent. Also, the specificities were 100 per cent (25/25) for both 50 and 57 per cent, and 96 per cent (24/25) for 75 per cent. Although the low cut-off levels of 50 per cent and 57 per cent had low sensitivities, they yielded a high specificity (100%) compared to the higher level of 75 per cent. In the present study, the sensitivity of the cut-off level at 75 per cent was much lower than that of the study by Knobe and Ljung (93%) since the presented sample size of obligate carriers was rather small. So, enrollment of more subjects should be further carried out. In conclusion, FIX:C determination alone showed a limitation in the diagnosis of hemophilia B carriers. The addition of genetic analysis of linkage analysis or mutation detection is required for a definite diagnosis.

Factor VIII, factor IX and fibrinogen content in cryoprecipitate, fresh plasma and cryoprecipitate-removed plasma.

In order to provide accurate information for physicians, factor VIII, factor IX and fibrinogen content were determined in 40 bags of cryoprecipitate, fresh plasma and cryoprecipitate-removed plasma. A cryoprecipitate bag with a volume of 21.8 +/- 5.3 ml contained 139.5 +/- 42.9 units of factor VIII and 200.0 +/- 80.0 mg of fibrinogen. Fresh plasma with a volume of 208.0 +/- 22.5 ml contained 180.9 +/- 45.3 of factor IX, significantly higher than in cryoprecipitate-removed plasma. It was also found in this study that group O blood showed a significantly lower level of factor VIII.

Protocolo para el estudio de las hemofilias A y B en Medellín / Protocol for the study of hemophilia A and B in Medellín

Se informan los resultados de un protocolo para el estudio de las hemofilias A y B. Se cuantifica el nivel de FVIII: C y FIX: C por la prueba de una etapa y con base en ello se establece la severidad de la enfermedad en 26 pacientes hemofílicos previamente conocidos como tales con base en las pruebas de coagulación más sencillas. Se discute la utilidad de nuestro perfil biológico en el estudio de pacientes con historia sugestiva de estas coagulopatías hereditarias