OBJECTIVES: The Fetal Anomaly Screening Programme (FASP) will include NIPT for pregnant women whose first or second-trimester screen test for trisomy 21, 18 and 13 produces a “higher-chance” risk score (≥ 1:150). NIPT reduces invasive testing (IT) and procedure-related miscarriages and complications (PRMC), stimulating a debate on the cut-off score. This study compared the clinical and economic outcomes of adding NIPT to the current screening regimen with standard care (SC) from a UK NHS perspective. Scenario analysis evaluated the impact of different risk cut-offs and screening approaches.

METHODS: Decision analytic modelling was used to determine the short-term and five-year costs and outcomes of women with singleton pregnancies >10 weeks gestational age (n=800,561). Literature-based key assumptions included a 66% uptake of prenatal screening and a 72% uptake of IT after a positive prior screen. Sensitivity and specificity is trisomy and test-dependent but assumed 100% for IT.

RESULTS: Contingent on a risk score ≥ 1:150, adding NIPT reduces IT, and PRMC by 50% vs. SC, while saving £2078 per trisomy detected, despite a 3% increase in missed trisomies (due to NIPT’s slightly lower sensitivity for T18 and T13 vs. IT). Changing the threshold risk score to 1:300 or 1:1000 reduced missed trisomies by >45% compared with SC while reducing IT and PRMC by >45% and saving £4939 per trisomy detected (1:300) or increasing costs by £30 per woman screened (1:1000). Offering NIPT first-line (at 1:150 cut-off) was the only approach to reduce trisomy-affected births but significantly increased costs. Varying the NIPT false-positive rate from 0.1% to 1% increased IT, PRMC and costs.

CONCLUSIONS: Introducing second-line NIPT in higher-risk pregnancies produces the expected reductions in IT and PRMC. However, a risk cut-off of 1:300 or 1:1000 increases the total number of trisomies detected while reducing IT and PRMC.