Table 5. Performance results of the proposed diagnostic algorithm with different ACR score thresholds, T, for HIV-infected (N = 128) patients only.
| ACR threshold T | Selected for Xpert (%) | Sensitivity (%) | Specificity (%) | PPV (%) | NPV (%) | CSS ($) | CNTBC ($) |
|---|---|---|---|---|---|---|---|
| 0 | 100 | 65.8 | 95.6 | 86.2 | 86.9 | 13.09 | 67.02 |
| 17 | 90 | 60.5 | 96.7 | 88.5 | 85.3 | 13.22 | 73.58 |
| 35 | 80 | 60.5 | 97.8 | 92.0 | 85.4 | 11.89 | 66.18 |
| 44 | 70 | 55.3 | 97.8 | 91.3 | 83.8 | 10.66 | 65.00 |
| 54 | 60 | 52.6* | 97.8 | 90.9 | 83.0 | 9.33 | 59.74 |
| 73 | 50 | 52.6* | 97.8 | 90.9 | 83.0 | 8.01 | 51.23 |
| 85 | 40 | 50.0* | 98.9 | 95.0 | 82.4 | 6.68 | 44.97 |
| 95 | 30 | 44.7* | 98.9 | 94.4 | 80.9 | 5.35 | 40.25 |
| 98 | 20 | 34.2* | 100.0 | 100.0 | 78.3 | 4.12 | 40.56 |
The first row matches a scenario where all subjects undergo Xpert and no ACR.
ACR, automated chest radiography; CNTBC, cost per notified TB case; CSS, cost per screened subject; NPV, negative predictive value; PPV, positive predictive value; Xpert, Xpert MTB/RIF.
*Sensitivity significantly different from Xpert standalone, T = 0. (p < 0.05 considered significant).