Triple-Marker Screening of Serum for Down's Syndrome

To the Editor: Haddow et al. (April 21 issue) 1 report that among pregnant women 35 years of age or older, screening serum for three substances (alpha-fetoprotein, human chorionic gonadotropin, and estriol) can identify 89 percent of fetuses with Down's syndrome, with a false positive rate of 25 percent. We must distinguish how these results relate to individual women (i.e., the effect on patient care) from their effect in larger populations (i.e., the implications for public policy). The authors seem to suggest that preference should be given to the latter. The practicing physician is concerned with individual pregnant women. The challenge . . .