Background
Methods
Overview of RNTCP services
The modelling framework
Indicator | Calibration target |
---|---|
Incidence in 2015 | 217 (112–355) per 100,000 population |
Prevalence in 2015 | 253 (195–312) per 100,000 population |
Proportion MDR | 3.1% (2.6–3.7) (averaged over new and retreatment cases) |
Cumulative notifications to public sector (1997–2015) | 19.61 million (17.65–21.57 million) (allowing for 10% error) |
Out of the above, cumulative MDR notifications (2007–2015) | 92,753 (83,478–102,028) (allowing for 10% error) |
Transmission model structure
Parameter name | Symbol | Value | Note/source |
---|---|---|---|
Average number of infections per drug-susceptible (DS) TB case per year |
β
| 10.7 [5.8–13.6] | Estimated |
Average number of infections per MDR-TB case per year |
β
mdr
| 2.00 [1.62–2.62] | Estimated |
Per care seeking attempt, probability of seeking care in the public sector (following RNTCP scale-up) |
p
max
| 0.34 [0.25–0.58] | Estimated to get reported notifications from 1997–2015 |
Proportion of MDR-TB cases whose drug resistance is recognized at the point of TB diagnosis and who start appropriate treatment |
q
max
| 0.07 [0.06–0.09] | Estimated to get reported notifications from 2007–2015 |
Reduction in force of infection owing to previous infection |
C
| 0.5 | Assumed |
Proportion of infections undergoing ‘rapid’ progression |
k
| 0.15 | Vynnycky and Fine, 1997 [42] |
Rate of breakdown from remote infection to active disease |
h
| 0.001 y-1
| Horsburgh et al., 2010 [43] |
Rate corresponding to the delay from the start of symptoms to the initiation of treatment (whether in public or private sector) |
r
| 3.29 y-1 [0.83–5.70] | Estimated |
Mean duration of first-line treatment |
\( {\uptau}_{\mathrm{FL}} \)
| 2 y-1
| Corresponding to 6 months of treatment duration |
Rate of default from non-RNTCP treatment |
d
RNTCP
| 1.06 y-1
| Uplekar et al. 1998 [29] |
Rate of default from RNTCP treatment |
d
non-RNTCP
| 0.049 y-1
| Corresponds to 4.8% default in RNTCP (TB India, 2015 [34]) (averaged over smear-positive, smear-negative and extrapulmonary TB) |
Rate of repeat care seeking after recurrence or failure |
w
| 4 y-1
| Corresponds to 3 months of delay period |
Annual recurrence rate |
\( \uprho \)
| 0.003 y-1
| Corresponds to lifetime recurrence risk of 17% (Sun et al., 2013 [44]) |
Rate of primary MDR acquisition from patient treated under RNTCP |
m
| 0.02 y-1
| TB India, 2015 [34] |
Mean duration of second-line treatment |
\( {\uptau}_{\mathrm{SL}} \)
| 0.5 y-1
| Corresponding to 2 years of treatment duration |
Spontaneous cure rate |
\( \upsigma \)
| 0.166 y-1
| Corresponds to 50% spontaneous cure in 3 years alongside with TB mortality (Tiemersma et al., 2011 [26]) |
Proportion cure of drug-susceptible (DS)-TB in RNTCP after first-line treatment |
α
pub
| 0.87 | TB India, 2015 [34] |
Proportion cure of DS-TB in non-RNTCP after first-line treatment |
α
prv
| 0.51 | Uplekar et al., 1998 [29] |
Proportion cure of MDR-TB in RNTCP after first-line treatment (excluding self-cure) |
α’
pub
| 0.24 | TB India, 2015 [34] |
Proportion cure of MDR-TB in non-RNTCP after first-line treatment |
α’
prv
| 0 | Assumed |
Proportion cure of MDR-TB with second-line treatment (excluding self-cure) |
α’
pub2
| 0.48 | TB India, 2014 [45] |
Per-capita mortality hazard before diagnosis |
μ
UTB
| 0.086 (95% CI 0.075–0.11) y-1
| See Additional file 1
|
Mortality hazard during RNTCP treatment |
μ
RNTCP
| 0.076 (95% CI 0.069–0.095) y-1
| See Additional file 1
|
Mortality hazard during non-RNTCP treatment |
μ
non-RNTCP
| 0.27 (95% CI 0.22–0.33) y-1
| See Additional file 1
|
Mortality hazard following default and treatment failure |
μ
B
| 0.28 (95% CI 0.22–0.36) y-1
| See Additional file 1
|
Capturing scale-up of RNTCP services
Epidemiological data
Mortality hazards
Estimating lives saved
Results
Direct effects | Indirect effects | Total lives saved | |
---|---|---|---|
DS-TB lives saved | 3.53 million (95% CrI* 2.86–4.11 million) | 2.57 million lives (95% CrI 1.80–3.09 million) | 6.25 million lives (95% CrI 4.96–7.14 million) |
MDR-TB lives saved | 0.71 million (95% CrI 0.61–0.79 million) | 0.76 million (95% CrI 0.60–0.96 million) | 1.50 million lives (95% CrI 1.22–1.74 million) |
Total lives saved | 4.23 million lives (95% CrI 3.52–4.89 million) | 3.28 million lives (95% CrI 2.58–4.02 million) | 7.75 million lives (95% CrI 6.29–8.82 million) |