Test result | Prevalence PET (%) | Probability of PET after testing positive (%) | Risk of PET after treatment* | Probability of PET after treatment | NNTest1 | NNTreat2 |
---|---|---|---|---|---|---|
No test, no treatment3 | 3.0 | 3.0 | - | 3.0 | - | - |
 | 10.0 | 10.0 |  | 10.0 |  |  |
No test, treat all3 | 3.0 | - | 0.9 | 2.8 | - | 323 |
 | 10.0 | - | 0.9 | 9.0 | - | 90 |
Alpha feto-protein>2.0MoM: Sensitivity 7%; Specificity 96% | ||||||
Test all, treat test positives | 3.0 | 7.3 | 0.9 | 6.1 | 4762 | 147 |
 | 10.0 | 26.2 | 0.9 | 18.6 | 1429 | 48 |
Human chorionic gonadotrophin>2.0MoM, second trimester: Sensitivity 19%; Specificity 93% | ||||||
Test all, treat test positives | 3.0 | 7.5 | 0.9 | 6.3 | 1754 | 142 |
 | 10.0 | 27.2 | 0.9 | 19.3 | 526 | 47 |
Unconjugated estriol<0.5MoM: Sensitvity 6%; Specifcitiy 96% | ||||||
Test all, treat test positives | 3.0 | 4.6 | 0.9 | 4.0 | 5556 | 226 |
 | 10.0 | 16.7 | 0.9 | 12.8 | 1667 | 70 |
Pregnancy associated plasma protein A (PAPP-A)<5th centile: Sensitivity 9%; Specificity 95% | ||||||
Test all, treat test positives | 3.0 | 6.5 | 0.9 | 5.5 | 3704 | 167 |
 | 10.0 | 23.3 | 0.9 | 17.0 | 1111 | 53 |
Inhibin A>2.79MoM: Sensitivity 71%; Specificity 96%. | ||||||
Test all, treat test positives | 3.0 | 6.0 | 0.9 | 3.4 | 469 | 27 |
 | 10.0 | 216.9 | 0.9 | 61.2 | 141 | 15 |