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 with different short tandem repeat (STR) markers of the X chromosome (SBMA, DXS8377 and DXS1283E) together with the amelogenin locus (AMXY) was developed for the rapid detection of sex chromosome aneuploidies on uncultured amniotic 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 uninformative cases, an additional STR marker was applied. The QF-PCR data were compared with the results of conventional cytogenetics. One dark red stained specimen showed an artificial PCR pattern, probably due to maternal contamination. 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 detected by the assay. In all, 12 cases with a numerical aberration involving either 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 chromosome 18 and an uninformative third STR marker. Two samples with an unbalanced Robertsonian translocation could be identified by QF-PCR as trisomic for chromosomes 13 and 21 respectively. The results show an excellent agreement between QF-PCR and cytogenetics with regard to sex chromosome and autosomal aneuploidy detection in prenatal diagnosis.