Table 1: Publicly funded prenatal screening tests in Ontario*1
Screening modalityTimingMarkers analyzedDetection rate, %False-positive rate, %
First-trimester combined screeningwk 11–13NT, PAPP-A, fbhCG835
Integrated prenatal screening1st phase: wk 11–13NT, PAPP-A871.9
2nd phase: wk 15–20AFP, hCG, uE3
Serum integrated prenatal screening1st phase: wk 11–13PAPP-A854.4†
2nd phase: wk 15–20AFP, hCG, uE3, DIA
Four-marker second-trimester serum screening (QUAD)wk 15–20AFP, hCG, uE3, DIA775.2

Note: AFP = α-fetoprotein, DIA = dimeric inhibin-A, fbhCG = free-β subunit of human chorionic gonadotropin, hCG = human chorionic gonadotropin, NT = nuchal translucency, PAPP-A = pregnancy-associated plasma protein A, uE3 = unconjugated estriol.
*Other available tests are AFP only for open neural tube defect, NT only for multiple pregnancies, and PAPP-A plus second-trimester QUAD test when NT is not available (i.e., in remote areas) in the first trimester. Noninvasive prenatal testing is available free of charge to women who have a high-risk pregnancy and for a fee to women who do not have a high-risk pregnancy.
†The false-positive rate is an estimate, given the small volume of uptake of this screening test in the province.1