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A NEW SCREENING STRATEGY FOR DOWN'S SYNDROME.

Pregnant women in the U.S. are generally offered amniocentesis or chorionic villus sampling starting at age 35, when the risk of Down's syndrome roughly equals the risk of amniocentesis-related fetal loss. This study compared routine amniocentesis with a screening strategy using maternal serum markers to estimate the risk of Down's syndrome.

About 5400 pregnant women aged 35 years or older underwent amniocentesis and three serum tests (alpha-fetoprotein, unconjugated estriol, and human chorionic gonadotropin). There were 54 cases of Down's syndrome diagnosed by amniocentesis.

When the cutoffs for abnormal serum tests were adjusted to correspond with a risk of 1 in 200, the serum markers identified 89 percent of Down's cases with a 25 percent false positive rate. If only the women with "abnormal" serum tests had received amniocentesis, 48 of the 54 Down's cases would have been identified, 75 percent of the 5400 women would have avoided amniocentesis, and there would have been about 20 fewer amniocentesis-related miscarriages.

Comment: This study clearly shows that screening with serum testing could markedly reduce amniocentesis, at the price of missing a small number of Down's cases. But as two editorialists point out, the acceptance of this strategy depends on patients' values and assumes that 35 is the appropriate age to start screening.

— AS Brett

Published in Journal Watch General Medicine April 29, 1994

Citation(s):

Pauker SP; Pauker SG. Prenatal diagnosis--why is 35 a magic number. N Engl J Med 1994 Apr 21 330 1151-1152.

• Original article (Subscription may be required)
• Medline abstract (Free)

Haddow JE et al. Reducing the need for amniocentesis in women 35 years of age or older with serum markers for screening. N Engl J Med 1994 Apr 21 330 1114-1118.

• Original article (Subscription may be required)
• Medline abstract (Free)