Table 2. Parameter estimates used in the model.
| Parameter | Base Value | Range for Sensitivity Analysis | Reference |
| TB dynamicsa | |||
| Probability of death, untreated smear-positive TB | 0.70 | 0.5–0.95 | [4] |
| Probability of death, untreated smear-negative TB | 0.20 | 0.15–0.25 | [4] |
| Secondary TB infections per year, smear-positive TB | 10 | 8–12 | [24] |
| Relative infectiousness of smear-negative TB | 0.22 | 0.16–0.28 | [37] |
| Fraction of new TB cases that are smear-positive | 0.53 | 0.4–0.66 | [4] |
| Characteristics of TB diagnosis | |||
| Prevalence of active TB among persons with suspected active TB | 0.14 | 0.11–0.18 | [19] |
| Sensitivity of clinician diagnosisb | 0.53 | 0.40–0.67 | [26] |
| Sensitivity for smear-positive TB, serology (anda-TB) | 0.76 | 0.63–0.87 | [14] |
| Sensitivity for smear-negative TB | |||
| MGIT TB culture (single specimen) | 0.73 | 0.55–0.91 | [23] |
| Serology | 0.59 | 0.40–0.85 | [14] |
| Specificity for active TB | |||
| Clinician diagnosisb | 0.94 | 0.75–1.0 | [3] |
| Sputum smear microscopy (two smears) | 0.97 | 0.9–1.0 | [6] |
| MGIT TB culture | 0.99 | 0.95–1.0 | [23] |
| Serology | 0.87 | 0.74–0.98 | [14] c |
| Time to TB diagnosis | |||
| MGIT TB culture | 8 wk | 1–4 mo | [20] |
| Sputum smear, serology | 1 wk | 3–14 d | [38],[39] |
| Loss to follow-up | |||
| MGIT TB culture | 0.25 | 0.19–0.31 | Estimated |
| Sputum smear, serology | 0.15 | 0.11–0.19 | [40],[41] |
| Characteristics of TB treatment | |||
| Proportion of treated TB patients who die | 0.045 | 0.033–0.056 | [26] |
| Proportion of treated HIV/TB patients who die | 0.090 | 0.068–0.114 | [26] |
| Proportion of treated TB patients infectious at 1 y | 0.045 | 0.033–0.056 | [26] |
| HIV/TB | |||
| HIV prevalence, general population | 0.3% | 0.225%–0.4% | [18] |
| HIV prevalence, patients with TB | 5.3% | 4.0%–6.6% | [26] |
| Proportion of HIV-infected patients with ART access | 0.10 | 0.075–0.125 | [18] |
| Costs and effectiveness, US$ | |||
| Unit cost, independent laboratory | |||
| Sputum smear microscopy (two smears) | US$3.62 | US$1–US$5 | [19] |
| TB culture (MGIT) | US$20 | US$10–US$30 | [21] |
| Serology | US$20 | US$10–US$30 | [19] |
| Mean cost of treating one case of TB | US$82.40 | US$60–US$100 | [26] |
| DALY weightsa | |||
| Active TB | 0.264 | 0.198–0.330 | [42] |
| TB treatment | 0.132 | 0.099–0.165 | Estimated |
| Life expectancy after TB cure (y) | 40 | 30–50 | [43],[44] |
a
Parameter values for HIV-positive patients are excluded from this table owing to low HIV prevalence but were incorporated into the model and can be found in reference [17].
b
In the absence of any TB-specific microbiological test.
c
Excludes studies not performed in developing countries.
ART, antiretroviral therapy.