OBJECTIVEInversions of intron 1 (Inv1) or intron 22 (Inv22) of the coagulation factor VIII gene (F8) may be found in 40%-50% of patients with severe hemophilia A. Such inversions cannot be detected by conventional sequencing. Due to homologous recombination, family-based linkage analysis may yield false positive or false negative results. In this study, Inverse-shifting PCR (IS-PCR) was used to detect potential inversions in two families affected with hemophilia A.

METHODSPeripheral venous blood, fetal amniotic fluid and fetal chorionic cells were harvested for genome DNA extraction. IS-PCR was used to detect Inv1 or Inv22 detection or its subtypes.

RESULTSIS-PCR has accurately detected Inv22 and Inv1 in both families and verified the subtypes of Inv22.

CONCLUSIONCarriers of Inv22 or Inv1 may be precisely detected with IS-PCR. The results have provided valuable information for genetic counseling and prenatal diagnosis for the affected families.