Detection of aneuploidy in chromosomes X, Y, 13, 18 and 21 by QF-PCR in 662 selected pregnancies at risk

A quantitative fluorescent-polymerase chain reaction (QF-PCR) test system w ith different short tandem repeat (STR) markers of the X chromosome (SBMA, DXS8377 and DXS1283E) together with the amelogenin locus (AMXY) was develop ed for the rapid detection of sex chromosome aneuploidies on uncultured amn iotic fluids. The samples (n = 662) were also tested with STRs specific for chromosomes 13, 18 or 21, with two STRs used for each chromosome. In uninf ormative cases, an additional STR marker was applied. The QF-PCR data were compared with the results of conventional cytogenetics. One dark red staine d specimen showed an artificial PCR pattern, probably due to maternal conta mination. Six sex chromosome aberrations (four 45,X, one 47,XXY, one mosaic 47,XXY/46,XX) were identified as aneuploid by STRs specific for chromosome X and AMXY. One pregnancy with a mosaic 45,X/46,XX karyotype was not detec ted by the assay. In all, 12 cases with a numerical aberration involving ei ther chromosome 18 or 21 or with a triploidy were correctly diagnosed by QF -PCR. No information was obtained in one fetal sample with a trisomy 18 due to an uncertain result for two of the three applied STRs specific for chro mosome 18 and an uninformative third STR marker. Two samples with an unbala nced Robertsonian translocation could be identified by QF-PCR as trisomic f or chromosomes 13 and 21 respectively. The results show an excellent agreem ent between QF-PCR and cytogenetics with regard to sex chromosome and autos omal aneuploidy detection in prenatal diagnosis.