Table 3.
Sensitivity, Specificity, Positive predictive Value, Negative Predictive Value at different CAD4TB score thresholds among individuals tested using Xpert MTB/RIF, visiting TB diagnostic and treatment centers in Karachi, Pakistan (Q3–2013 to Q2–2015).
| CAD Score | Sensitivity | Specificity | PPV | NPV | Xpert tests saved | Total Xpert tests | TB Cases Missed | MTB+ | MTB Yield |
|---|---|---|---|---|---|---|---|---|---|
| No Triage Test | |||||||||
| — | — | — | — | — | — | 6,090 | — | 925 | 15.2% |
| Model 1: CAD4TB Only (AUC 0.79, 95% CI: 0.78–0.81) | |||||||||
| 50 | 97.3% | 30.3% | 20.0% | 98.4% | 1590 | 4500 | 25(2.7%) | 900(97.3%) | 20.0% |
| 80 | 91.0% | 50.7% | 24.9% | 96.9% | 2702 | 3388 | 83(9.0%) | 842(91.0%) | 24.9% |
| 90 | 85.0% | 65.8% | 30.8% | 96.1% | 3539 | 2551 | 139(15.0%) | 786(85.0%) | 30.8% |
| Model 2: CAD4TB, Symptoms (AUC 0.81, 95% CI: 0.79–0.82) | |||||||||
| 50 | 96.75% | 30.37% | 19.92% | 98.12% | 1601 | 4489 | 30 (3.2%) | 894(96.8%) | 19.9% |
| 80 | 87.45% | 61.40% | 28.85% | 96.47% | 3289 | 2801 | 116(12.5%) | 808(87.5%) | 28.8% |
| 90 | 73.05% | 75.75% | 35.03% | 94.01% | 4163 | 1927 | 249(26.9%) | 675(73.1%) | 35.0% |
| Model 3: CAD4TB, Age, Gender (AUC 0.83, 95% CI: 0.82–0.85) | |||||||||
| 50 | 96.3% | 34.8% | 20.9% | 98.1% | 1829 | 4261 | 34(3.7%) | 891(96.3%) | 20.9% |
| 80 | 82.3% | 66.9% | 30.8% | 95.5% | 3620 | 2470 | 164(17.7%) | 761(82.3%) | 30.8% |
| 90 | 65.8% | 82.5% | 40.2% | 93.1% | 4577 | 1513 | 316(34.2%) | 609(65.8%) | 40.2% |
| Model 4: CAD4TB, Age, Gender, Symptoms (AUC 0.84, 95% CI: 0.82–0.85) | |||||||||
| 50 | 95.8% | 37.5% | 21.5% | 98.0% | 1973 | 4117 | 39(4.2%) | 886(95.8%) | 21.5% |
| 80 | 82.8% | 68.5% | 32.0% | 95.7% | 3695 | 2395 | 159(17.2%) | 766(82.8%) | 32.0% |
| 90 | 69.1% | 80.9% | 39.3% | 93.6% | 4465 | 1625 | 286(30.9%) | 639(69.1%) | 39.3% |