[Maternal serum alpha-fetoprotein as a screening test for fetal Down syndrome]

An association between a low maternal serum alpha-fetoprotein (MSAFP) level and an increased incidence of Down syndrome is well documented. This study was undertaken to elucidate the diagnostic efficacy of MSAFP as a screening test for Down syndrome in 711 Japanese women who underwent genetic amniocentesis between 14 and 20 gestational weeks of age in Hyogo Medical College Hospital. The mean value for the multiple of the median (MoM) of the MSAFP level in 11 pregnancies associated with Down syndrome was 0.78 +/- 0.47 and 1.12 +/- 0.67, respectively. A cut-off value of < 0.45, < 0.50, < 0.55 and < 0.60 MoM yielded negative predictive values of 98.6%, 98.5%, 99.0% and 99.2%, positive predictive values of 6.3%, 4.0%, 9.1% and 8.6%, a sensitivity of 9.1%, 9.1%, 36.4% and 54.5%, and false positive rates of 2.1%, 3.4%, 5.7% and 9.1%, respectively. The combining of MSAFP and maternal age improves the expected results of a strategy for Down syndrome.