[Application of long distance-PCR to hemophilia A carrier detection and prenatal diagnosis].

Objective To establish an effective laboratory examination system for carrier detection and prenatal diagnosis of haemophilia A (HA). Methods Twenty-five carriers of severe HA were directly detected by long-distance PCR(LD-PCR) in search of the factor Ⅷ(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. Results Eight out of 25 cases were diagnosed as having FⅧ gene inversion. 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. Conclusion LD-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.