Maternal serum placental growth factor and α-fetoprotein testing in first trimester screening for Down syndrome

Objective The aim of this research was to evaluate the addition of first trimester maternal serum placental growth factor (PlGF) and -fetoprotein (AFP) to the combined test for Down syndrome and a serum only protocol of PlGF, AFP, free -human chorionic gonadotropin and pregnancy-associated plasma protein-A. Methods Samples were from 92 Down syndrome cases with 552 matched controls. All women had a combined test at 1114weeks gestation. PlGF and AFP were measured and expressed in multiples of the gestation-specific median (MoM), adjusting for maternal weight and smoking status. Multivariate Gaussian modeling was used to predict detection and false-positive rates. Results The median PlGF level in the cases was 0.694 MoM and controls 1.000 MoM (p=<0.0001). The corresponding values for AFP were 0.764 MoM and 0.990 MoM (p<0.0001). Statistical modeling predicted that for a given false-positive rate, the addition of PlGF to the combined test increases the detection rate by 47%. For a given detection rate, the false-positive rate could be almost halved. When both PlGF and AFP are used, the detection rate increase is 58%. A serum only protocol had a predicted a detection rate of 71% for a false-positive rate of 5%. Conclusions Results suggest a substantial benefit of adding PlGF to the combined test. (c) 2013 John Wiley & Sons, Ltd.