Rapid direct diagnosis of deletions carriers of Duchenne and Becker muscular dystrophies

13 families and 34 women at risk of being carriers of Duchenne and Becker muscular dystrophies were analysed blind by restriction fragment length polymorphisms (RFLPs) and a new, non-radioactive direct test based on competitive polymerase-chain reaction (PCR) amplification. All obligate carriers were correctly diagnosed by RFLPs and competitive PCR, and 7 women with a 99% risk of being carriers were also diagnosed carriers by competitive PCR. There were no false positives or false negatives. Only 1 PCR result was noninformative. Our test allows rapid, precise, and direct carrier diagnosis of women whose relatives have a known deletion of the dystrophin gene.