Molecular genetic testing of hemophilia A.

Genetic testing in hemophilia A continues to diversify. This article describes recent advances in several aspects of genetic analysis and its interpretation and reporting. The intron 1 and 22 inversions responsible for 50% of severe hemophilia A cases can be sought using long and inverse polymerase chain reaction (PCR) techniques. Point mutations are analyzed in remaining patients by PCR amplification of the F8 protein-coding region followed by either mutation screening to identify the mutated amplicon and subsequent DNA sequencing or by directly sequencing amplified DNA. Many technique modifications and sequence analysis software packages are available to reduce time and effort required to identify a mutation. Dosage analysis and gap PCR have been described to identify carriers of large F8 deletions. Noninvasive prenatal fetal sex determination and preimplantation genetic diagnosis extend the reproductive options available to hemophilia carriers. Guidelines on undertaking and reporting the testing plus external quality assessment are now available to help ensure that genetic analysis yields accurate and well-interpreted results.