First-trimester screening proves 'accurate, reliable': (Detection rate for trisomy 21 is 85.2% with a false-positive rate of 9.4%. (Nuchal Translucency, Biochemistry, Age).

NEW ORLEANS -- First trimester aneuploid screening using maternal age, biochemistry, and nuchal translucency measurement is "possible, accurate, and reliable," and should be more widely adopted, Dr. Ronald Wapner said at the annual meeting of the Society for Maternal-Fetal Medicine.

He based that comment on results of a multicenter study involving 8,215 women who underwent first-trimester screening using this approach. The detection rate for trisomy 21 was 85.2% with a false-positive rate of 9.4%. "A false-positive cutoff of 5% still gave us a detection rate of 78.7%, and at a 1% false-positive rate we still maintained a 64% detection rate for trisomy 21," said Dr. Wapner, who conducted the study along with his colleagues in the Biochemistry Ultrasound, and Nuchal Translucency Study Group.

The study demonstrated better performance than second trimester screening in allowing patients to have earlier diagnosis and therefore additional reproductive options, said Dr. Wapner of MCP-Hahnemann School of Medicine, Philadelphia.

With second-trimester screening, a diagnosis of aneuploidy may be delayed until late in the second trimester, making termination more difficult both medically and emotionally.

The study, which was sponsored by the National Institute of Child Health and Human Development, involved participants from 12 North American centers. They underwent biochemistry screening for pregnancy-associated plasma protein-A and free [beta]-hCG, as well as ultrasound for nuchal translucency measurement, between weeks 10 and 14 of gestation.

With these techniques, a total of 61 cases of trisomy 21 were identified during the first trimester. "With our maternal age distribution we would have anticipated 48.5 cases," Dr. Wapner said.

Preliminary reports have demonstrated a potential detection rate as high as 90% for trisomy 21 with false-positive rates between 5% and 7.5% for first-trimester screening.