First-trimester screening for Down syndrome using nuchal translucency measurement with free beta-hCG and PAPP-A between 10 and 13 weeks of pregnancy--the combined test.
In a population of 1467 women attending the 'G. Gaslini' Institute for antenatal care, we evaluated first-trimester risk screening for Down syndrome using the 'combined test' based on ultrasound measurement of nuchal translucency (NT), maternal serum pregnancy-associated plasma protein A (PAPP-A) and free beta-hCG, and maternal age. No clinical action was taken on these results. The gestational age, determined by scan measurement of crown rump length, ranged from 10 weeks to 13 weeks 6 days. The median maternal age was 31 years 8 months. There were 13 Down syndrome pregnancies. The risk of having an affected pregnancy was estimated from a multivariate Gaussian distribution, using commercially available software. With a risk cut-off of 1 in 350, 11 affected pregnancies were detected (detection rate 85 per cent, 95 per cent confidence interval: 56-100 per cent) with a 3.3 per cent false-positive rate. The odds of being affected given a positive result were 1 in 30. Further data are needed to determine, with greater statistical reliability, the relative performance of the combined test with current second-trimester screening.
D000328:Adult; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D004314:Down Syndrome / Q000097:blood / Q000175:diagnosis* / Q000000981:diagnostic imaging; D005260:Female; D005865:Gestational Age; D006801:Humans; D008423:Maternal Age; D009333:Neck / Q000000981:diagnostic imaging*; D011247:Pregnancy; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis*; D012307:Risk Factors; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal