Does the addition of unconjugated estriol in maternal serum screening improve the detection of trisomy 21? A meta-analysis

At present there is controversy over the addition of unconjugated estriol to maternal serum screening for trisomy 21. To resolve the controversy, we posed the hypothesis that there is no difference in sensitivity or specificity between a triple screen (α-fetoprotein, human chorionic gonadotropin, and unconjugated estriol) and a double screen (α-fetoprotein and human chorionic gonadotropin) in detecting a fetus with Down's syndrome. To test the hypotheses we conducted an analysis of prospective studies in the available literature. This technique was used because the occurrence of trisomy 21 is a rare event in pregnancy, making it difficult to arrive at a definitive conclusion on the basis of a single study. Using the statistical technique of meta-analysis, we have determined that the addition of unconjugated estriol does improve the detection of trisomy 21.