Combined serum and nuchal translucency screening in the first trimester achieves 85% to 90% detection rate for Down and Edward syndromes

Abstract

Question How accurate is combined screening, based on maternal age, using serum and nuchal translucency measurements in first trimester screening for Down and Edward syndromes? Study design Cohort study. Main results Combined screening identified 85.2% (95% CI 73.8 to 93.0%) of babies with Down syndrome with a false positive rate of 9.4% (95% CI 8.8 to 10.1%). In women over 35 years, 89.8% cases were identified and the false positive rate increased to 15.2%. Combined screening identified 90.9% (95% CI 58.7 to 99.8%) of babies with Edward syndrome (trisomy 18) with a false positive rate of 2% (95% CI 1.7 to 2.3). All cases of trisomy 18 were identified among women over 35 years ( n=8). Combined screening was significantly better than use of serum markers alone ( p=0.002) but no more accurate than use of nuchal translucency alone ( p=0.28). Authors’ conclusions Combined screening for Edward and Down syndromes during the first trimester achieved detection rates of 90% and 85%, respectively, with acceptable false positive rates.