First-trimester down screening gaining ground: nuchal translucency, serum markers.(Obstetrics)

Atlanta -- First-trimester screening for Down syndrome using nuchal translucency measurements and serum markers will soon be the standard of care, Dr. Ray O. Bahado-Singh predicted at a conference on high-risk obstetrics sponsored by Symposia Medicus.

"I anticipate that in a very short time in vasive testing for Down syndrome will be very much the exception rather than the rule. It is pretty clear, at least from preliminary data, that we will be able to identify well in excess of 90% of affected fetuses in the first trimester," he said.

The anticipated shift from second-to first-trimester screening for chromosomal abnormalities is expected to follow the release of U.S. data from the First and Second Trimester Evaluation of Risk (FASTER) trial in early 2004. Half of perinatologists are already doing first-trimester screening, Dr. Bahado-Singh said. "The reality is that even without the official designation of gold standard, [first-trimester screening] is already being widely used in the community," he said.

Compelling European data generated considerable controversy as to whether first-trimester screening should be adopted as the standard of care in the United States. "The American College of Obstetricians and Gynecologists weighed in on the issue in 1999, saying that nuchal translucency plus serum markers appears promising but the technique needs to be standardized, and that until further studies were done, particularly in the United States, it couldn't be recommended for routine use," he said.

In one large multicenter study in England, nuchal translucency screening alone in the first trimester had a sensitivity of 70% for detection of Down syndrome with a false-positive rate of 4.6% (Lancet 352[9125]:343-46, 1998).

"Compare this with the midtrimester triple screen plus maternal age, which has about a 60% sensitivity. ...