Table 3.
The detection performance of STSS and NIPT for Down syndrome in different maternal age groups.
| Description of parameters | NIPT performance | STSS performance | ||||
|---|---|---|---|---|---|---|
| All | Maternal age < 35 years | Maternal age ≥ 35 years | All | Maternal age < 35 years | Maternal age ≥ 35 years | |
| TP | 163 | 100 | 63 | 83 | 33 | 50 |
| FP | 35 | 28 | 7 | 11,218 | 7,265 | 3,953 |
| TN | 140,062 | 120,522 | 19,540 | 128,879 | 113,285 | 15,594 |
| FN | 5 | 3 | 2 | 85 | 70 | 15 |
| Sensitivity (95% CI) |
97.02% (94.45–99.59%) |
97.09% (93.84–100%) |
96.92% (92.73–100%) |
49.41% (41.85–56.97%) |
32.04% (23.02–41.05%) |
76.92% (66.68–87.17%) |
| Specificity (95% CI) |
99.98% (99.97–99.98) |
99.98% (99.97–99.99%) |
99.96% (99.94–99.99%) |
91.99% (91.85–92.14%) |
93.97% (93.84–94.11%) |
79.78% (79.21–80.34%) |
| PPV (95% CI) |
82.32% (77.01–87.64%) |
78.13% (70.96–85.29%) |
90.00% (82.97–97.03%) |
0.73% (0.58–0.89%) |
0.45% (0.30–0.61%) |
1.25% (0.91–1.59%) |
| NPV (95% CI) |
99.99% (99.99–100%) |
99.99% (99.99–100%) |
99.99% (99.98–100%) |
99.93% (99.92–99.95%) |
99.94% (99.92–99.95%) |
99.90% (99.86–99.95%) |
| FPR | 0.03% | 0.02% | 0.04% | 8.01% | 6.03% | 20.22% |
| FNR | 2.98% | 2.91% | 3.08% | 50.60% | 67.96% | 23.08% |
CI, confidence interval; PPV, positive predictive value; NIPT, non-invasive prenatal testing; TP, true positives; NPV, negative predictive value; STSS, second-trimester serum screening; FP, false positives; FPR, false positive rate; TN, true negatives; FN, false negatives; FNR, false negative rate.