Multiple screening for fetal Down's syndrome with the classic triple test,dimeric inhibin A and ultrasound

The aim of the study was to determine whether inhibin combined with ultraso und improves the classic second trimester triple test. Eighteen Down's synd rome and 200 euploid pregnancies were included. Maternal serum ci-fetoprote in (AFP), human chorionic gonadotrophin (hCG), and estriol (E-3), measured between 15 and 20 weeks' gestation by radioimmunoassay, were retrieved. Inh ibin A was tested with a specific two-monoclonal-antibody ELISA. Ultrasound was performed between 15 and 25 weeks' gestation: femur length, nuchal thi ckness and morphological abnormalities were assessed. Statistical analysis used a multivariate discriminant analysis. Except for the classic triple te st parameters, only inhibin and the standard deviation score (SDS) for femu r length allowed us to make a statistically significant distinction between euploid and Down's syndrome pregnancies. For a 5% false-positive rate, the classic triple test sensitivity was 61%. When E-3 was replaced with inhibi n A, the sensitivity increased to 77.8% and to 66.7% with SDS femur length. Combining hCG, AFP, SDS femur length and inhibin A gave a sensitivity of 6 6.7% for a false-positive rate of 2.5%. In conclusion, the classic triple t est can be more significantly improved by replacing E-3 with inhibin than b y including ultrasound. However, a combination of ultrasound and inhibin en hances both the sensitivity and specificity of the test. In Down's syndrome screening, the biological parameters improve sensitivity while ultrasound is a better indication of specificity. Copyright (C) 2000 S. Karger AG, Bas el.