[Blood screening for Down's syndrome in women under 35 years of age with an age-independent index].

The need for alternatives to amniocentesis, beset by 1% abortion rate, has been increasingly voiced over the past years and also includes the under 35 age group. However, the known age-dependent screening programs such as Alpha program according to Wald (1988) and the Dermalog Program according to Norgaard-Pederson (1990) only yield a detection rate of 50 or, at best, 70% (Müller, 1992) for this age group. We tried to improve this result by index calculation. Compared to the tested age-dependent screening programs the Ulm Index achieves a 25 to 40% higher detection rate (85%). For pregnant women beyond 35 years the detection rate of Down's syndrome can even be raised to 95-100% by a combination of the Alpha or Dermalog program with the Ulm Index, without entailling an increase in the rate of false-positive results.