Rapid detection of chromosome aneuploidies by quantitative fluorescence PCR: first application on 247 chorionic villus samples

We report the results of the first major study of applying quantitative flu orescence polymerase chain reaction (QF-PCR) assays for the detection of ma jor chromosome numerical disorders. The QF-PCR tests were performed on a to tal of 247 chorionic villus samples, which were analysed blind, without any knowledge of the results obtained using conventional cytogenetic analysis. The aims of this investigation were to evaluate the detection power and acc uracy of this approach by testing a large number of fetal samples and to as sess the diagnostic value of each of the chromosome specific small tandem r epeat (STR) markers used. In addition, we introduced three more markers spe cific for chromosomes 13, 18, and X to allow an accurate analysis of sample s homozygous for a particular STR. Fluorescent labelled primers were used t o amplify 12 STRs specific for chromosomes 21, 18, 13, X, and the amylogeni n-like DNA sequence AMXY expressed on the X and Y chromosomes. In this blin d study of 247 fetal samples, 222 were correctly diagnosed by QF-PCR as nor mal for each of the five chromosomes investigated; 20 were diagnosed by QF- PCR as trisomic for chromosomes 21, 18, or 13, in agreement with the cytoge netic tests. Only one false negative result was observed, probably owing to the mishandling of the sample, which had been transferred through three la boratories before being analysed by QF-PCR. The 247 samples also included f our cases of mosaicism or translocation; one case of mosaic trisomy 21 was detected by QF-PCR and the other cases were not identified by QF-PCR. The results of this investigation provide clear evidence that the QF-PCR as says are powerful adjuncts to conventional cytogenetic techniques and can b e applied for the rapid and accurate prenatal diagnosis of the most frequen t aneuploidies.