Tuberculosis (TB) remains an important global cause of mortality and morbidity. In low‑incidence, high‑income settings such as Canada, much TB disease among migrants reflects progression of infections acquired before immigration. Most existing cost‑effectiveness analyses of systematic screening and TB preventive treatment (TPT) consider only acute TB outcomes during the treatment period and commonly omit longer‑term post‑TB health consequences.
Emerging evidence indicates that survivors of TB experience elevated healthcare utilization and higher long‑term risks of illness and death compared with those who never had TB. Global analyses suggest post‑TB consequences account for a substantial share of TB‑related health burden. Omitting these longer‑term outcomes could therefore underestimate the health gains and cost‑effectiveness of interventions that prevent TB disease.
This study models how incorporating post‑TB consequences influences estimates of effectiveness and cost‑effectiveness for an expanded postarrival TB infection screening program among persons recently immigrating to Canada.
The authors developed a Markov microsimulation model to simulate the health trajectories, costs, and outcomes for a cohort of persons immigrating to Canada in 2025. The model population was 400,000 persons (rounded from Canada’s 2025 immigration target of 395,000) and was structured by age and country of origin using distributions for new permanent residents in 2024.
Model outcomes included quality‑adjusted life years (QALYs), TB episodes, TB deaths, and TB‑related costs. The analysis used a 25‑year time horizon, discounted outcomes and costs at 1.5% per annum, and adopted a TB services perspective for costing.
Canada is a low TB incidence country; in 2024 it reported 2,508 persons with TB disease (incidence 6.1 per 100,000 population). Migrants account for the majority of TB in Canada—83% of TB cases were born outside Canada. Current immigration medical examinations focus on detecting active TB disease before entry; systematic postarrival screening and treatment for TB infection for all recent immigrants are not provided provincially or territorially, and only 0.5% of persons with clinical risk factors receive postarrival screening under current practice.
The model’s simplified health states and structure are described in the article appendix. Time to progression from infection to disease after immigration was parameterized using Public Health Agency of Canada data.
The comparator (status quo) represents current low postarrival screening levels (0.5%). The intervention is a scaled program in which all new permanent residents from countries with annual TB incidence >50 per 100,000 would be invited to postarrival TB infection screening. Screening in both strategies used the tuberculin skin test. Persons with a positive test in the intervention would be offered TPT, specified as 4 months of daily rifampin. The model assumed 68% uptake among those invited to screening, based on adherence evidence from other postarrival follow‑up programs for immigrants.
Where possible, parameter values and uncertainty distributions were sourced from systematic reviews, high‑quality randomized trials, and Canadian surveillance and costing studies. Most TB cost inputs derived from a pan‑Canada costing study and were expressed in 2023 Canadian dollars, inflated using consumer price indices. Acute QALY loss for TB (excluding death) was parameterized as an annualized loss of 0.057. Probabilities of age‑specific mortality during acute TB and other epidemiologic inputs used Canadian surveillance and published literature; additional parameter tables and model structure are provided in the appendix.
Primary outcomes were QALYs, TB episodes, TB deaths, and TB‑related costs over 25 years. Costs and outcomes were discounted at 1.5% per year, aligned with Canadian guidance. The analysis reported incremental outcomes and cost per QALY comparing the scaled screening and TPT intervention with status quo.
When the model included only acute TB consequences, estimated TB‑related QALYs lost were lower than when post‑TB consequences were included. Incorporating long‑term TB‑related death, illness, and healthcare costs increased estimated TB‑related QALYs lost by 2.1‑fold (95% uncertainty range 1.7–2.5‑fold).
Accounting for post‑TB consequences also increased the estimated health gains from the expanded screening program: QALYs gained from the intervention rose 2.4‑fold (95% uncertainty range 1.6–4.4‑fold) compared with analyses that omitted long‑term outcomes. Including post‑TB consequences reduced the estimated cost per QALY of expanded screening from CAD $235,088 to CAD $100,742.
These changes indicate that ignoring post‑TB morbidity and mortality materially underestimates both the health benefits and cost‑effectiveness of screening and TPT among recent immigrants.
In low‑incidence, high‑income settings where a large proportion of TB cases occur among persons born abroad, preventive interventions targeting recently arrived migrants may yield greater health benefits and be more cost‑effective than previously estimated if post‑TB consequences are considered. The findings support consideration of comprehensive cost‑effectiveness evaluations that include longer‑term TB sequelae when planning postarrival screening and TPT programs.
The study also highlights gaps in current practice: Canada’s postarrival screening coverage is currently very low (0.5%), and systematic programs for TB infection among recent immigrants are uncommon across provinces and territories.
This modeling analysis demonstrates that including long‑term post‑TB consequences substantially increases estimated QALYs lost to TB and the QALYs gained from preventive interventions, and markedly improves estimated cost‑effectiveness of expanded postarrival screening and TPT among new immigrants to Canada. The authors recommend that future economic evaluations of TB prevention should incorporate post‑TB health consequences because omitting them can lead to substantial underestimation of program benefits and value for money.