Table 3.
Empirical results
| 1 in 100 | 1 in 250 | |||
|---|---|---|---|---|
| FPR (95% CI) |
DR (95% CI) |
FPR (95% CI) |
DR (95% CI) |
|
| (i) maternal age, PAPP-A & free B-hCG | 2.9 (1.5, 4.2) |
72.2 (65.7, 78.7) |
9.4 (7.0, 11.8) |
86.2 (79.0, 93.3) |
| (ii) maternal age, PAPP-A, free B-hCG & ADAM12-S | 2.6 (1.3, 3.9) |
73.7 (67.7, 79.6) |
9.3 (7.0, 11.7) |
87.3 (80.4, 94.2) |
| (iii) maternal age, PAPP-A, free B-hCG & NT | 0.6 (0.1, 1.2) |
71.1 (61.8, 80.5) |
2.8 (1.5, 4.1) |
83.7 (75.7, 91.8) |
| (iv) maternal age, PAPP-A, free B-hCG, NT & ADAM12-S | 0.7 (0.1, 1.3) |
71.1 (61.8, 80.5) |
2.6 (1.4, 3.8) |
87.7 (80.4, 94.9) |
| (v) maternal age, PAPP-A & ADAM12-S | 2.5 (1.4, 3.7) |
56.8 (50.1, 63.5) |
9.2 (6.9, 11.4) |
73.7 (63.6, 83.8) |
| (vi) maternal age, PAPPA, ADAM12-S & NT | 1.4 (0.6, 2.3) |
75.1 (67.2, 83.1) |
3.5 (2.2, 4.9) |
81.4 (75.3, 87.6) |
Results for a screening test including maternal age, PAPP-A and ADAM12-S, with and without NT. These results are empirical values, standardised to a reference maternal age population (UK 2000 to 2002). Detection rates and false-positive rates for fetal trisomy 21 at fixed risk cut-offs of 1 in 100 and 1 in 250 are given. Figures in brackets are 95% confidence intervals. Substantial decrease in DR when first trimester free B-hCG in (i) is replaced with ADAM12-S to give (v), with a negligible decrease in FPR.
Substituting free B-hCG in the combined test (iii) for ADAM12-S to give (vi), gives a slightly higher DR and FPR at a risk cut-off of 1 in 100, and a slightly lower DR and higher FPR at a risk cut-off of 1 in 250.