Carrier detection and feasibility of prenatal diagnosis of hemophilia B by multiplex polymerase chain reaction

Since direct diagnosis based on detection of factor IX mutations by direct sequencing is currently performed in a few laboratories only, restriction fragment length polymorphisms are still useful for carrier detection and prenatal diagnosis of hemophilia B. We analyzed 29 women from 20 families at risk of hemophilia B with three intragenic (MnlI, DdeI, TaqI) and two extragenic (HhaI, BamHI) restriction fragment length polymorphisms, all by the polymerase chain reaction. This analysis confirmed 10 possible carriers and excluded 16 as carriers. The diagnosis was made in 17 of the 20 families (85%). The combination of three polymorphisms indicated that MnlI/DdeI/HhaI and TaqI/DdeI/HhaI were the most informative (15/20 families, 75% and 14/20 families, 70%). For carrier detection with the most useful polymorphism combination (TaqI/DdeI/HhaI) we devised a multiplex polymerase chain reaction that uses two or three sets of primers, allowing carrier diagnosis in one step with 99% reliability. Our results indicate that the combination of five restriction fragment length polymorphisms makes carrier detection and prenatal diagnosis possible for 85% of families at risk of hemophilia B, with 99% reliability. With multiplex polymerase chain reaction such diagnoses can be obtained faster.