A prospective comparative study on fluorescence in situ hybridization (FISH) of uncultured amniocytes and standard karyotype analysis.

Fluorescence in situ hybridization (FISH) on uncultured amniocytes and standard cytogenetic analysis after amniocentesis have been performed for 904 samples. The experience with the FISH method and its clinical relevance is described in a large clinical pilot study. Commercially available chromosome-specific DNA probes for chromosomes 13, 18, 21, X and Y were used. FISH assays were performed from 12 weeks of gestation to the third trimester. In 96 per cent of the cases, hybridization was performed successfully. At least 50 nuclei for all probes could be counted in 88 per cent of the cases and in 8 per cent between 10 and 49 nuclei were scored. All trisomies 13, 18 and 21 and all cases with gonosomal aberrations were detected by FISH analysis with the exception of one case of trisomy 21 in which hybridization failed due to technical problems. Neither false-positive nor false-negative results were obtained with the DNA probes, in complete agreement with standard cytogenetics. In our experience, FISH is a valuable and reliable method for rapid diagnosis. Consequences of FISH diagnosis are discussed.