DNA Blood Test Could Rule Out Down Syndrome

Maternal plasma DNA sequencing could help rule out Down syndrome in high-risk pregnancies, according to a BMJ study.

Researchers recruited pregnant women at high risk and also examined archived maternal plasma samples of women in whom chorionic villus sampling or amniocentesis were clinically indicated. Some 750 maternal plasma samples then underwent sequencing to detect fetal DNA concentration of chromosome 21.

Compared with the gold standard of full karyotyping from chorionic villus samples or amniocentesis, maternal plasma DNA sequencing achieved 100% sensitivity and 97.9% specificity.

The authors, who have filed patent applications for detection of fetal nucleic acids in maternal plasma, say that 98% of invasive diagnostic procedures could be eliminated if referrals for these procedures were based on sequencing results. They predict that the test could eventually become a first-tier screening tool, even for women at low risk for trisomy 21. However, the test is currently expensive.