OBJECTIVETo establish an effective laboratory examination system for carrier detection and prenatal diagnosis of haemophilia A (HA).

METHODSTwenty-five carriers of severe HA were directly detected by long-distance PCR (LD-PCR) in search of the factor FVIII (FVIII) gene inversion. Prenatal diagnosis was carried out using pregnant woman's venous blood sample, husband's venous blood sample and fetal navel venous sample at 20-24 weeks of gestation. The plasma coagulation factor VIII activity (FVIII:C) was detected by one-stage method. The concentration of von Willbrand factor (Vwf) was assayed by ELISA. Prenatal diagnosis was finally made by LD-PCR. The results of LD-PCR were proved by DNA sequencing.

RESULTSEight out of 25 cases were diagnosed as having FVIII geneinversion. Four of these 8 carriers underwent the LD-PCR for prenatal diagnosis, and 2 of them had to terminate pregnancy because their fetuses were diagnosed as having HA. The other two carriers were finally diagnosed to have normal fetuses by combined use of LD-PCR with plasma FVIII:C, vWF in pregnant woman's venous blood, husband's venous blood and fetal navel venous blood, and the one-year follow-up study demonstrated that the babies were normal and living well.

CONCLUSIONLD-PCR technique was adopted in this study to detect the factor VIII gene inversion; it could accurately and rapidly diagnose the severe cases of HA and could be used for the HA carriers in need of pregnant diagnosis.