Impact of replacing or adding placental growth factor on Down syndrome screening: A prospective cohort study

Objectives: To assess whether adding placental growth factor (PlGF) or replacing pregnancy-associated plasma protein-A (PAPP-A) improves the first trimester combined test performance for trisomy 21. Methods: A total of 11,518 women with a singleton pregnancy who underwent the first trimester combined test between December 2016 and December 2019 were included. PlGF was measured and estimated term risk for trisomy 21 was calculated by (1) adding PlGF to the combined test and (2) replacing PAPP-A with PlGF. Results: Twenty-nine pregnancies had trisomy 21. The combined tests detection rate (DR), false positive rate (FPR) and screen positive rate (SPR) were 89.7%, 5.7% and 6% respectively. DR when adding PlGF to the combined test or replacing PAPP-A remained unchanged. Replacing PAPP-A by PlGF increased FPR and SPR to 6.2% and 6.4% respectively. Adding PlGF to the combined test gave FPR and SPR rates of 5.5% and 5.7% respectively. Change in FPR and SPR was not significant (p > 0.1 for all). Conclusion: Adding PlGF to the combined test or replacing PAPP-A with PlGF did not improve trisomy 21 DR and resulted in a non-significant marginal change in FPR and SPR.