Nuchal translucency, serum testing: trial backs early screening for Down syndrome; Results may lead to shift in standard of care for those desiring an early, noninvasive test.(News)

NEW ORLEANS -- First-trimester Down syndrome screening was at least as effective as second-trimester screening in a major U.S. trial expected to pave the way for a shift in the standard of care for pregnant women who desire an early, noninvasive method to assess fetal risk of the disorder.

The First and Second Trimester Evaluation of Risk (FASTER) trial involved about 38,000 pregnant women at 15 centers who underwent combined first-trimester screening with nuchal translucency measurement and serum testing for the biochemical markers pregnancy-associated plasma protein A (PAPP-A) and free [beta]-HCG. The women also underwent second-trimester quad screening; second-trimester screening is the current standard of care.

A total of 84 babies were born with Down syndrome in this study. The detection rate for combined first-trimester screening was 83% with a false-positive rate of 5.6%, and the detection rate for second-trimester screening was 85% with a false-positive rate of 8.5%; these differences were not statistically significant. The best results were achieved using both first- and second-trimester testing, which yielded a 94% detection rate and 11% false positive rate, Dr. Fergal D. Malone reported at the annual meeting of the Society for Maternal-Fetal Medicine.

First-trimester screening was conducted between 10 3/7 weeks' and 13 6/7 weeks' gestation, although the optimal time for testing was 11 weeks, because nuchal translucency was shown to deteriorate rapidly as a marker between 11 and 13 weeks. Second-trimester screening was conducted between 15 and 18 weeks' gestation. Participants with any positive screen were offered genetic counseling and amniocentesis, said Dr. Malone of Columbia University, New York.

"The FASTER trial shows that both first-trimester combined screening and second-trimester quad screening are similarly effective for Down syndrome. Additionally, integrated screening across both the first and second trimester is the most efficient test in cases when [chorionic villi sampling] is either not desired or not readily available," he said, noting that these and other findings from ...