Microarrays beat karyotyping in prenatal diagnosis

In a head-to-head trial, chromosomal microarray analysis was shown to be more effective than traditional karyotyping in prenatal diagnosis. Results of the study-which is the largest of its kind and which received support from the National Institutes of Child Health and Human Development-reflect the accuracy, efficacy, and incremental yield of the technologies.

Contemporary OB/GYN editorial board member Joe Leigh Simpson, MD, is a coauthor of the study.

In the study, samples from 4406 women undergoing prenatal diagnosis at 29 centers were sent to a central karyotyping laboratory. Each sample was split in 2, with standard karyotyping performed on 1 portion and chromosomal microarray analysis performed on the second portion by 1 of 4 laboratories. The microarray platform and technology were in keeping with standards for 2007, when the research began; the analysis was not changed during the study.

The indication for prenatal diagnosis was advanced maternal age in 46.6% of the women, an abnormal result on Down syndrome screening in 18.8%, structural anomalies on ultrasound in 25.2%, and other indications in 9.4% of the women. Microarray analysis was successful in 98.8% of the fetal samples and identified all aneuploidies and unbalanced rearrangements seen on karyotyping but not balanced translocations and fetal triploidy. In samples with a normal karyotype, microarray analysis revealed clinically relevant deletions or duplications in 6% with a structural anomaly and in 1.7% for which the indication for screening was advanced maternal age or positive screening results.

The researchers concluded that when used for prenatal diagnosis, chromosomal microarray analysis identified more cytogenetic information that was clinically significant than did karyotyping. It was just as efficacious, they said, in identifying aneuploidies and unbalanced rearrangements but did not identify balanced translocations and triploidies.