Table 3. Performance of non-invasive prenatal testing according to the pregnancy trimester.
| Aneuploidies | 1st trimester (n = 462) | 2nd trimester (n = 593) | ||||||
|---|---|---|---|---|---|---|---|---|
| Sensitivity, % | Specificity, % | PPV, % | NPV, % | Sensitivity, % | Specificity, % | PPV, % | NPV, % | |
| Trisomy 21 | 100 | 100 | 100 | 100 | 100 | 99.8 | 94.7 | 100 |
| (39/39) | (423/423) | (39/39) | (423/423) | (18/18) | (574/575) | (18/19) | (574/574) | |
| Trisomy 18 | 92.3 | 100 | 100 | 99.3 | 100 | 100 | 100 | 100 |
| (36/39) | (423/423) | (36/36) | (423/426) | (3/3) | (590/590) | (3/3) | (590/590) | |
| Trisomy 13 | 100 | 100 | 100 | 100 | 100 | 99.8 | 50.0 | 100 |
| (8/8) | (454/454) | (8/8) | (454/454) | (1/1) | (591/592) | (1/2) | (591/591) | |
| Total | 96.5 | 100 | 100 | 99.2 | 100 | 99.6 | 91.7 | 100 |
| (83/86) | (376/376) | (83/83) | (376/379) | (22/22) | (569/571) | (22/24) | (569/569) | |
PPV = positive predictive value, NPV = negative predictive value.