Prenatal detection of aneuploidy by directly labeled multicolored probes and interphase fluorescence in situ hybridization.

OBJECTIVE

To detect aneuploidy of chromosomes 13, 18, 21, X, and Y with use of new, directly labeled, multicolored, commercially available DNA probes from interphase cells of amniotic fluid (AF).

MATERIAL AND METHODS

The hybridization sites of the five probes were validated by metaphase analysis. The fluorescence in situ hybridization (FISH) normal range was determined from a series of normal AF specimens and tested on a series of normal and abnormal specimens.

RESULTS

The hybridization efficiencies of the five probes were 100%. The mean AF interphase disomic signal patterns for chromosomes 13, 18, 21, XX, and XY were 95.9%, 89.1%, 94.3%, 94.7%, and 98.7%, respectively. Of a total of 508 cases analyzed, 211 were aneuploid. All cases were correctly identified and no false results occurred (in comparison with karyotypic analysis), although maternal cell contamination was relatively common.

CONCLUSION

Clinical screening for aneuploidy of chromosomes 13, 18, 21, X, and Y from interphase AF cells is possible with use of these probes and FISH. Cases of maternal cell contamination and mosaicism necessitate cautious interpretation. The FISH procedure is recommended for screening of common aneuploidies, followed by a complete chromosome analysis to detect anomalies.