Table 3 Selected outcomes from applying 1- and 2-test diagnostic strategy models to three HBV epidemic scenarios. The examples here have been extracted from Additional file 1
Population: 10,000 | |||||||
|---|---|---|---|---|---|---|---|
Strategy | HBsAg Test Kit | True Positive | False Positive | False Negative | PPV | number of assay B tests | |
Scenario 1 Prevalence 10%: | 1-test | 1 | 980 | 90 | 20 | 0.916 | |
2-test | 1 → 6 | 960 | 1 | 40 | 0.999 | 1070 | |
1-test | 2 | 900 | 90 | 100 | 0.909 | ||
2-test | 2 → 5 | 810 | 1 | 190 | 0.999 | 990 | |
Scenario 2 Prevalence 2%: | 1-test | 1 | 196 | 98 | 4 | 0.667 | |
2-test | 1 → 6 | 192 | 1 | 8 | 0.995 | 294 | |
1-test | 2 | 180 | 98 | 20 | 0.647 | ||
2-test | 2 → 5 | 162 | 1 | 38 | 0.994 | 278 | |
Scenario 3 Prevalence 0.4% | 1-test | 1 | 39 | 100 | 1 | 0.282 | |
2-test | 1 → 6 | 38 | 1 | 2 | 0.975 | 139 | |
1-test | 2 | 36 | 100 | 4 | 0.265 | ||
2-test | 2 → 5 | 32 | 1 | 8 | 0.970 | 136 | |
Test Kit Performance Characteristics: | |||||||
Test Kits | Sensitivity | Specificity | |||||
1 and 6 | 98.0% | 99.0% | |||||
2 and 5 | 90.0% | 99.0% | |||||
Notes on Two-Test Strategies: | |||||||
Assay B performance is considered independent of Assay A | |||||||
Outcome of 2-test strategy: A + B+ = pos and A-, A + B- = neg (Fig. 2) | |||||||
2-test strategies overall performance: | Assay A | Assay B | Sensitivity | Specificity | |||
1 | 6 | 96.04% | 99.99% | ||||
2 | 5 | 81.00% | 99.99% | ||||