Background
Methods
Model overview
Dynamic model
Decision analysis model
Data inputs for the decision analysis model
TB pathogenetic and epidemiologic parameters
Estimates | Reference | |
---|---|---|
Probabilities | Probability (%)* | |
•Probability of diagnosing LTBI | 25 | Assumption |
•Probability of completing LTBI treatment among those who start it | 70.8 | [69] |
•Probability of reactivation of longstanding LTBI to TB disease (non-smokers) | 0.05/year | |
•Probability of rapid progression following TB infection (non-smokers)** | 4.5/year for 2 years | Dynamic model# |
•Probability of diagnosing active disease | 90 | Assumption |
•Probability of spontaneous resolution of untreated TB disease | 25 | [16] |
•Probability of relapse following spontaneously resolved TB | 2.5 | |
•Probability of dying from untreated TB | 19/year | |
•Probability of relapse after treated TB disease in first year | 1.5 | [76] |
•Protective immunity from previous TB disease | 55 | Dynamic model# |
QALYs for LTBI and active TB | Value (range) | |
•Utility score for individual with active disease (treated) | 0.85 (0.70–0.90) | [40] |
•Utility score for individual with active disease (untreated) | 0.68 (0.65–0.72) | [39] |
•Utility score for individual with latent infection, during treatment | 0.97 (0.95–1.00) | [40] |
•Utility score for individual with latent infection (untreated) | 1 | Assumption† |
Tobacco use as a risk factor for TB
Tobacco reduction strategies
Scenario name | Brief description of strategy | Expected reduction in smoking prevalence* | Duration of intervention and its effect | Reference |
---|---|---|---|---|
Pharmacotherapy and counselling | Pharmacotherapy intervention to stop smoking comprised of 12 weeks nicotine replacement therapy (NRT) and varenicline medication. Group and individual counselling was offered to participants to enhance odds of quitting. Content and duration of counselling sessions were obtained from a meta-analysis of smoking cessation interventions with individuals undergoing treatment or recovery and dosage of varenicline and NRT prescriptions were modelled as per Inuit and Canadian standards. | 1.5% per year for 3 years | One time opportunity for smokers to join pharmacotherapy and counselling programs. Benefit was assumed to last for 3 years (i.e., smoking prevalence falls at an annual rate of 1.5% for 3 consecutive years). Beyond this period the prevalence declines at the background rate of 0.8% annually. | |
Pharmacotherapy, counselling and mass media | Pharmacotherapy and counselling components of this strategy were similar to the above strategy. We used pooled risk ratios for cessation from two randomized trials involving Indigenous people in Australian communities receiving national tobacco campaigns supplemented by other Indigenous specific campaigns such as “Break the chain”. | 1.9% per year for 3 years | One time opportunity for smokers to join pharmacotherapy and counselling programs accompanied by a mass media campaign. Benefit was assumed to last for 3 years (i.e., smoking prevalence falls at an annual rate of 1.9% for 3 consecutive years). Beyond this period the prevalence declines at the background rate of 0.8% annually. | [49] |
Increased taxation on commercial cigarettes | A legislative approach to commercial tobacco control through increased taxation which has no associated costs from the perspective of the healthcare system. To measure the impact of this policy change vis-à-vis commercial cigarette demand; we used reported price elasticity of demand (i.e., the extent to which cigarette use falls or rises after increases or decreases in price) | 7% after 3 years increasing to 14% after 10 years† | One time 25% increase in tobacco taxation was assumed to have greater immediate effect in the first 3 years and the effect would then decline over time (i.e., smoking prevalence decreases by 7% over 3 years, and after 10 years it decreases by a total of 14%). Beyond this period the prevalence declines at the background rate of 0.8% annually. | |
All strategies (Taxation + mass media + pharmacotherapy + Counselling) | Multifaceted strategy combining all the above strategies: the measure of effect of reduction in smoking prevalence is derived from the effect of increased taxation multiplied by 3-year effect (risk ratio) of pharmacotherapy combined with mass media | 5.6% annually for 3 years and 2.6% annually for subsequent 7 years | 5.6% annual reduction in smoking prevalence for the first 3 years followed by 2.6% annual reduction up to year 10 after one-time interventions. Beyond this period the prevalence declines at the background rate of 0.8% annually. |
Health utilities
Costs
Value | Range | Reference | |
---|---|---|---|
Health system costs (including material and health care worker time/salary) | |||
•Tuberculin skin test | $18.22 | [82] | |
•INH (9-month regimen) | $182.01 | [83] | |
•Major adverse reaction to Isoniazid | $14,937 | [82] | |
•Chest X-ray | $68.00 | [84] | |
•Three sputum samples analysis (when results are negative) | $29.34 | Dynacare | |
•Three sputum samples analysis (when results are positive) | $80.79 | Dynacare | |
•Spontaneous sputum production | $3.52 | (2.65–4.41) | [41] |
•Sputum induction | $96.84 | [42] | |
•Xpert® MTB/RIF test for one individual (1 sample) | $134.40 | [41] | |
•Standard 6 month TB medication regimen* | $640.84 | [83] |
Costs associated with specific tobacco reduction scenarios | Component cost | Per person cost of intervention | Reference |
---|---|---|---|
1) Increased taxation† | $0 | ||
2) Pharmacotherapy and counselling | |||
a. Unit cost of NRT chewing gum | $0.25 | [83] | |
b. Number of doses of NRT chewing gum (N) | 1008 | [45] | |
c. Cost of treatment with NRT chewing gum (a*b) | $254.32 | ||
d. Unit cost of a nicotine patch | $2.68 | [83] | |
e. Number of doses of nicotine patch (N) | 84 | [45] | |
f. Cost of treatment with nicotine patch (d*e) | $225.00 | ||
g. Cost of one varenicline 0.5 mg pill | $1.72 | [83] | |
h. Number of doses of varenicline (N) | 317 | ||
i. Cost of treatment with varenicline (g*h) | $544.29 | ||
j. Number of counselling cessions | 12 | [46] | |
k. Duration of each counselling session | 42 min | [46] | |
l. Hourly Nurse wage | $81.39 | [41] | |
m. Cost for complete counselling sessions (j*k*l) | $683.68 | ||
n. Total cost of Pharmacotherapy and counselling (c + f + i + m) per person | $1707.29 | ||
o. Proportion of smokers who made a quit attempt | 14.14% | ||
Pro-rated mean cost of pharmacotherapy and counselling per smoker (n*o: applied to all smokers in the model cohort) | $241.41 | ||
3) Pharmacotherapy, counselling and mass media | |||
a. Total cost of pharmacotherapy and counselling | $1707.29 | ||
b. Proportion of smokers who made a quit attempt | 19.8% | ||
c. Recommended per capita expenditure on mass media campaigns | $2.05 | [47] | |
Prorated mean cost of pharmacotherapy and counselling per smoker (a*b + c): added to all smokers | $339.78 | ||
4) Multifaceted strategy—pharmacotherapy, counselling, mass media, and taxation | $339.78 |
Sensitivity analysis
One and two-way analyses
Results
Base case
Outcomes per 1000 persons | Cost (95% UR) | TB incidence (95% UR) | TB deaths (95% UR) | QALYs (95% UR) |
Status quo | $816,588 ($589,629–$1,144,728) | 18.88 (14.81–23.92) | 1.83 (1.12–3.30) | 14,963.00 (14,935.98–14,966.22) |
Increased taxation | $800,890 ($579,868–$1,120,755) | 18.43 (14.53–23.30) | 1.76 (1.11–3.16) | 14,963.66 (14,937.19–14,966.72) |
Pharmacotherapy and counselling | $955,921 ($726,763–$1,279,070) | 18.71 (14.71–23.68) | 1.80 (1.12–3.25) | 14,963.25 (14,936.45–14,966.41) |
Pharmacotherapy, counselling, and mass media | $1,012,812 ($782,975–$1,333,469) | 18.62 (14.65–23.56) | 1.79 (1.11–3.22) | 14,963.40 (14,936.71–14,966.52) |
All [taxation + mass media + pharmacotherapy + counselling] | $981,366 ($764,325–$1,283,894) | 17.72 (14.06–22.32) | 1.64 (1.03–2.93) | 14,964.76 (14,939.14–14,967.55) |
Costs per person and ICERs—status quo as comparator | Incr. cost vs status quo | Incr. cost per TB case averted | Incr. cost per TB death averted | Incr. cost per QALY gained |
Status quo [comparator] | – | – | – | – |
Increased taxation | Saves $16 ($8 - $26) | Dominant | Dominant | Dominant |
Pharmacotherapy and counselling | $142 ($125–$146) | $837,464 ($527,624–$1,462,565) | $4,990,117 ($2,495,571–$8,928,090) | $542,594 ($259,691–$812,827) |
Pharmacotherapy, counselling, and mass media | $200 ($175–$206) | $760,387 ($478,141–$1,330,478) | $4,530,453 ($2,264,728–$8,115,767) | $492,482 ($235,705–$738,813) |
All [taxation + mass media + pharmacotherapy + counselling] | $181 ($157–$196) | $142,907 ($78,263–$271,386) | $852,009 ($398,407–$1,594,941) | $93,717 ($41,304–$147,677) |
ICERs per person—increased taxation as a comparator | Incr. cost vs Increased taxation | Incr. cost per TB case averted | Incr. cost per TB death averted | Incr. cost per QALY gained |
Status quo | $16 ($8–$26) | Dominated | Dominated | Dominated |
Increased taxation [comparator] | – | – | – | – |
Pharmacotherapy and counselling | $155 ($139–$164) | Dominated | Dominated | Dominated |
Pharmacotherapy, counselling, and mass media | $212 ($192–$222) | Dominated | Dominated | Dominated |
All [taxation + mass media + pharmacotherapy + counselling] | $180 ($154–$195) | $256,022 ($151,962–$465,895) | $1,522,952 ($740,992–$2,789,202) | $164,369 ($76,252–$252,203) |
Outcomes per 1000 persons | Total cost | TB-related health system cost | Smoking intervention cost |
---|---|---|---|
Status quo | $816,588 | $816,588 | – |
Increased taxation | $800,890 | $800,890 | – |
Pharmacotherapy and counselling | $955,921 | $810,731 | $145,190 |
Pharmacotherapy, counselling, and mass media | $1,012,812 | $807,503 | $205,309 |
All [taxation + mass media + pharmacotherapy + counselling] | $981,366 | $776,057 | $205,309 |
Sensitivity analyses
Strategy | Cost | TB incidence | TB deaths | QALYs accrued |
---|---|---|---|---|
Pharmacotherapy interventions’ effectiveness lasts 5 years | ||||
Status quo—no new intervention | $816,588 | 18.88 | 1.83 | 14,963.00 |
Increased taxation | $800,890 | 18.43 | 1.76 | 14,963.66 |
Pharmacotherapy and counselling | $953,746 | 18.65 | 1.79 | 14,963.33 |
Pharmacotherapy, counselling, and mass media campaign | $1,009,480 | 18.52 | 1.77 | 14,963.52 |
Combination of all strategies | $977,469 | 17.61 | 1.62 | 14,964.90 |
Taxation (one time increase), pharmacotherapy, and mass media continued for 20 years | ||||
Status quo—no new intervention | $816,588 | 18.88 | 1.83 | 14,963.00 |
Increased Taxation | $800,890 | 18.43 | 1.76 | 14,963.66 |
Pharmacotherapy and counselling | $2,732,610 | 18.48 | 1.77 | 14,963.48 |
Pharmacotherapy, counselling, and mass media campaign | $3,444,542 | 18.27 | 1.73 | 14,963.73 |
Combination of all strategies | $3,047,175 | 17.36 | 1.58 | 14,965.13 |
Scenario where 50% of smokers attempt quitting and use pharmacotherapy services | ||||
Status quo—no new intervention | $816,588 | 18.88 | 1.83 | 14,963.00 |
Increased taxation | $800,890 | 18.43 | 1.76 | 14,963.66 |
Pharmacotherapy and counselling | $1,293,929 | 17.83 | 1.66 | 14,964.42 |
Pharmacotherapy, counselling, and mass media campaign | $1,288,847 | 17.63 | 1.62 | 14,964.74 |
Combination of all strategies | $1,226,645 | 15.87 | 1.33 | 14,967.53 |
Scenario where 75% of smokers attempt quitting and use pharmacotherapy services | ||||
Status quo—no new intervention | $816,588 | 18.88 | 1.83 | 14,963.00 |
Increased taxation | $800,890 | 18.43 | 1.76 | 14,963.66 |
Pharmacotherapy and counselling | $1,521,195 | 16.97 | 1.52 | 14,965.59 |
Pharmacotherapy, counselling, and mass media campaign | $1,512,916 | 16.68 | 1.47 | 14,966.07 |
Combination of all strategies | $1,433,675 | 14.46 | 1.09 | 14,969.78 |