PRENATAL SERUM SCREENING FOR DOWNS-SYNDROME

With the aid of two commercially available analysis programmes we effected non-invasive assessment of the risk for Down's syndrome in 597 pregnancies with healthy fetuses and in 22 pregnancies with trisomie 21-affected fetuses, maternal age ranging between 18 and 45 years. Based on the women's serum levels, hormone concentrations of AFP, free estriol and beta-HCG were determined, a multiple of their median was combined with the age factor, and the result used as a parameter for overall risk estimation. A risk cut-off-level greater then 1:250 was considered to represent a positive risk. For patients younger than 35 years test sensitivity, at just over 50%, was found to be low. For those aged 35 years or greater, however, the Dermalog programme was able to detect 94,4% and the Alpha programme 88,2% of fetuses affected by trisomy 21, with a false-positive rate of 19,6 and 19,1%, respectively. If the test were to be applied to all pregnant womens beyond 35 years of age the detection rate of Down's syndrome could be nearly doubled compared to today's figure (only 50%, of women in this age group undergo amniocentesis). By the same token the rate of amniocentesis-induced abortion (approx. 1%) could be reduced to about one third.