Cost-effectiveness of post-landing latent tuberculosis infection control strategies in new migrants to Canada

The prevalence of tuberculosis infection among foreign-born Canadians: a modelling study

BACKGROUND

The prevalence of tuberculosis infection is critical to the design of tuberculosis prevention strategies, yet is unknown in Canada. We estimated the prevalence of tuberculosis infection among Canadian residents born abroad.

METHODS

We estimated the prevalence of tuberculosis infection by age and year of migration to Canada for people from each of 168 countries by constructing country-specific and calendar year-specific trends for annual risk of infection using a previously developed model. We combined country-specific prevalence estimates with Canadian Census data from 2001, 2006, 2011, 2016 and 2021 to estimate the overall prevalence of tuberculosis infection among foreign-born Canadian residents.

RESULTS

The estimated overall prevalence of tuberculosis infection among foreign-born people in Canada was 25% (95% uncertainty interval [UI] 20%-35%) for census year 2001, 24% (95% UI 20%-33%) for 2006, 23% (95% UI 19%-30%) for 2011, 22% (95% UI 19%-28%) for 2016 and 22% (95% UI 19%-27%) for 2021. The prevalence increased with age at migration and incidence of tuberculosis in the country of origin. In 2021, the estimated prevalence of infection among foreign-born residents was lowest in Quebec (19%, 95% UI 16%-24%) and highest in Alberta (24%, 95% UI 21%-28%) and British Columbia (24%, 95% UI 20%-30%). Among all foreign-born Canadian residents with tuberculosis infection in 2021, we estimated that only 1 in 488 (95% UI 185-1039) had become infected within the 2 preceding years.

INTERPRETATION

About 1 in 4 foreign-born Canadian residents has tuberculosis infection, but very few were infected within the 2 preceding years (the highest risk period for progression to tuberculosis disease). These data may inform future tuberculosis infection screening policies.

Tuberculosis related barriers and facilitators among immigrants in Atlantic Canada: A qualitative study

Tuberculosis (TB) is a disease caused by the bacterium Mycobacterium tuberculosis and affects approximately one-quarter of the world's population. Immigrant populations in Canada are disproportionately affected by TB. Canada's immigration medical examinations include screening for active TB but not latent TB infection (LTBI). In LTBI, the bacterium remains dormant within the host but can reactivate and cause disease. Once active, TB can be transmitted to close contacts sharing confined spaces leading to the possibility of outbreaks in the broader community. This study aimed to 1) assess the current TB knowledge, perceived risk, and risk behaviors of immigrants in Atlantic Canada as well as 2) identify barriers and facilitators to testing and treatment of TB among this population. Three focus group discussions were conducted with a total of 14 non-Canadian born residents of New Brunswick aged 19 years and older. Data were analyzed using inductive thematic analysis. Four themes were identified from the data relating to barriers to testing and treatment of LTBI: 1) Need for education, 2) stigma, 3) fear of testing, treatment, and healthcare system, and 4) complacency. Results included reasons individuals would not receive TB testing, treatment, or seek help, as well as facilitators to testing and treatment. These findings may inform the implemention of an LTBI screening program in Atlantic Canada and more broadly across the country.

Screening for Tuberculosis Infection among Migrants: A Cost-Effectiveness Analysis in the Italian Context

BACKGROUND

Screening of tuberculosis infection (TBI) among migrants from high-incidence countries is a cornerstone of tuberculosis control in low-incidence countries. However, the optimal screening strategy has not been defined yet.

METHODS

A quasi-experimental study involving migrants residing in the province of Brescia was carried out that aimed at assessing the completion rate, time to completion, preventive treatment initiation rate, and cost-effectiveness of two strategies for TBI screening. They underwent TBI screening with the IGRA-only strategy (arm 1) or with the sequential strategy (tuberculin skin test, TST, followed by IGRA in case of a positive result-arm 2). The two strategies were compared in terms of screening completion, time to complete the screening process, therapy initiation, and cost-effectiveness.

RESULTS

Between May 2019 and May 2022, 657 migrants were evaluated, and 599 subjects were included in the study, with 358 assigned to arm 1 and 237 to arm 2. Screening strategy was the only factor associated with screening completion in a multivariable analysis, with the subjects assigned to the IGRA-only strategy more likely to complete the screening cascade (n = 328, 91.6% vs. n = 202, 85.2%, IRR 1.08, 95% CI (1.01-1.14), p = 0.019). The time to complete the screening process was significantly longer for patients assigned to the sequential strategy arm (74 days vs. 46 days, p = 0.002). Therapy initiation did not significantly differ between the two arms, and cost-effectiveness was higher for the sequential strategy.

CONCLUSION

Sequential strategy implementation for TBI screening among migrants may be justified by its higher cost-effectiveness in spite of the lower completion of the screening cascade.

A cost-effectiveness evaluation of latent tuberculosis infection screening of a migrant population in Malaysia

To estimate the costs and benefits of screening for latent tuberculosis infection (LTBI) in a migrant population in Malaysia. An economic model was developed from a Malaysian healthcare perspective to compare QuantiFERON-TB Gold Plus (QuantiFERON) with the tuberculin skin test (TST). A decision tree was used to capture outcomes relating to LTBI screening followed by a Markov model that simulated the lifetime costs and benefits of the patient cohort. The Markov model did not capture the impact of secondary infections. The model included an R shiny interactive interface to allow adaptation to other scenarios and settings. QuantiFERON is both more effective and less costly than TST (dominant). Compared with QuantiFERON, the lifetime risk of developing active TB increases by approximately 40% for TST due to missed LTBI cases during screening (i.e. a higher number of false negative cases for TST). For a migrant population in Malaysia, QuantiFERON is cost-effective when compared with TST. Further research should consider targeted LTBI screening for migrants in Malaysia based on common risk factors.

A systematic review of cost-utility analyses of screening methods in latent tuberculosis infection in high-risk populations

Background

The World Health Organisation (WHO) recommends that testing and treatment for latent tuberculosis infection (LTBI) should be undertaken in high-risk groups using either interferon gamma release assays (IGRAs) or a tuberculin skin test (TST). As IGRAs are more expensive than TST, an assessment of the cost-effectiveness of IGRAs can guide decision makers on the most appropriate choice of test for different high-risk populations. This current review aimed to provide the most up to date evidence on the cost-effectiveness evidence on LTBI testing in high-risk groups—specifically evidence reporting the costs per QALY of different testing strategies.

Methods

A comprehensive search of databases including MEDLINE, EMBASE and NHS-EED was undertaken from 2011 up to March 2021. Studies were screened and extracted by two independent reviewers. The study quality was assessed using the Bias in Economic Evaluation Checklist (ECOBIAS). A narrative synthesis of the included studies was undertaken.

Results

Thirty-two studies reported in thirty-three documents were included in this review. Quality of included studies was generally high, although there was a weakness across all studies referencing sources correctly and/or justifying choices of parameter values chosen or assumptions where parameter values were not available. Inclusions of IGRAs in testing strategies was consistently found across studies to be cost-effective but this result was sensitive to underlying LTBI prevalence rates.

Conclusion

While some concerns remain about uncertainty in parameter values used across included studies, the evidence base since 2010 has grown with modelling approaches addressing the weakness pointed out in previous reviews but still reaching the same conclusion that IGRAs are likely to be cost-effective in high-income countries for high-risk populations. Evidence is also required on the cost-effectiveness of different strategies in low to middle income countries and countries with high TB burden.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-02149-x.

Modeling the Cost-Effectiveness of Latent Tuberculosis Screening and Treatment Strategies in Recent Migrants to a Low-Incidence Setting

Many tuberculosis (TB) cases in low-incidence settings are attributed to reactivation of latent TB infection (LTBI) acquired overseas. We assessed the cost-effectiveness of community-based LTBI screening and treatment strategies in recent migrants to a low-incidence setting (Australia). A decision-analytical Markov model was developed that cycled 1 migrant cohort (≥11-year-olds) annually over a lifetime from 2020. Postmigration/onshore and offshore (screening during visa application) strategies were compared with existing policy (chest x-ray during visa application). Outcomes included TB cases averted and discounted cost per quality-adjusted life-year (QALY) gained from a health-sector perspective. Most recent migrants are young adults and cost-effectiveness is limited by their relatively low LTBI prevalence, low TB mortality risks, and high emigration probability. Onshore strategies cost at least $203,188 (Australian) per QALY gained, preventing approximately 2.3%-7.0% of TB cases in the cohort. Offshore strategies (screening costs incurred by migrants) cost at least $13,907 per QALY gained, preventing 5.5%-16.9% of cases. Findings were most sensitive to the LTBI treatment quality-of-life decrement (further to severe adverse events); with a minimal decrement, all strategies caused more ill health than they prevented. Additional LTBI strategies in recent migrants could only marginally contribute to TB elimination and are unlikely to be cost-effective unless screening costs are borne by migrants and potential LTBI treatment quality-of-life decrements are ignored.

Invited Commentary: The Role of Tuberculosis Screening Among Migrants to Low-Incidence Settings in (Not) Achieving Elimination

The cost-effectiveness of migrant tuberculosis prevention programs is highly relevant to many countries with low tuberculosis incidence as they attempt to eliminate the disease. Dale et al. (Am J Epidemiol. 2022;191(2):255-270) evaluated strategies for tuberculosis infection screening and treatment among new migrants to Australia. Screening for infection before migration, and then administering preventive treatment after arrival, was more cost-effective than performing both screening and treatment after arrival. From the Australian health payer perspective, the improved cost-effectiveness of premigration screening partly reflected the shift of screening costs to migrants, which may raise ethical concerns. Key sensitivity analyses highlighted the influence of health disutility associated with tuberculosis preventive treatment, and of posttreatment sequelae of tuberculosis disease. Both considerations warrant greater attention in future research. For all strategies, the impact on tuberculosis incidence among migrants was modest (<15%), suggesting enhanced migrant screening will not achieve tuberculosis elimination in low-incidence settings. This emphasizes the need to increase investment and effort in global tuberculosis prevention and care, which will ultimately reduce the prevalence of tuberculosis infection and therefore the risk of tuberculosis disease among migrants. Such efforts will benefit high and low tuberculosis incidence countries alike, and advance all countries further toward tuberculosis elimination.

Targeting screening and treatment for latent tuberculosis infection towards asylum seekers from high-incidence countries - a model-based cost-effectiveness analysis

Background

Enhancing tuberculosis (TB) prevention and care in a post-COVID-19-pandemic phase will be essential to ensure progress towards global TB elimination. In low-burden countries, asylum seekers constitute an important high-risk group. TB frequently arises post-immigration due to the reactivation of latent TB infection (LTBI). Upon-entry screening for LTBI and TB preventive treatment (TPT) are considered worthwhile if targeted to asylum seekers from high-incidence countries who usually present with higher rates of LTBI. However, there is insufficient knowledge about optimal incidence thresholds above which introduction could be cost-effective. We aimed to estimate, among asylum seekers in Germany, the health impact and costs of upon-entry LTBI screening/TPT introduced at different thresholds of country-of-origin TB incidence.

Methods

We sampled hypothetical cohorts of 30–45 thousand asylum seekers aged 15 to 34 years expected to arrive in Germany in 2022 from cohorts of first-time applicants observed in 2017–2019. We modelled LTBI prevalence as a function of country-of-origin TB incidence fitted to data from observational studies. We then used a probabilistic decision-analytic model to estimate health-system costs and quality-adjusted life years (QALYs) under interferon gamma release assay (IGRA)-based screening for LTBI and rifampicin-based TPT (daily, 4 months). Incremental cost-effectiveness ratios (ICERs) were calculated for scenarios of introducing LTBI screening/TPT at different incidence thresholds.

Results

We estimated that among 15- to 34-year-old asylum seekers arriving in Germany in 2022, 17.5% (95% uncertainty interval: 14.2–21.6%) will be latently infected. Introducing LTBI screening/TPT above 250 per 100,000 country-of-origin TB incidence would gain 7.3 (2.7–14.8) QALYs at a cost of €51,000 (€18,000–€114,100) per QALY. Lowering the threshold to ≥200 would cost an incremental €53,300 (€19,100–€122,500) per additional QALY gained relative to the ≥250 threshold scenario; ICERs for the ≥150 and ≥ 100 thresholds were €55,900 (€20,200–€128,200) and €62,000 (€23,200–€142,000), respectively, using the next higher threshold as a reference, and considerably higher at thresholds below 100.

Conclusions

LTBI screening and TPT among 15- to 34-year-old asylum seekers arriving in Germany could produce health benefits at reasonable additional cost (with respect to international benchmarks) if introduced at incidence thresholds ≥100. Empirical trials are needed to investigate the feasibility and effectiveness of this approach.

Cross-sectional study of prevalence and risk factors, and a cost-effectiveness evaluation of screening and preventive treatment strategies for latent tuberculosis among migrants in Singapore

OBJECTIVES

WHO recommends that low burden countries consider systematic screening and treatment of latent tuberculosis infection (LTBI) in migrants from high incidence countries. We aimed to determine LTBI prevalence and risk factors and evaluate cost-effectiveness of screening and treating LTBI in migrants to Singapore from a government payer perspective.

DESIGN

Cross-sectional study and cost-effectiveness analysis.

SETTING

Migrants in Singapore.

PARTICIPANTS

3618 migrants who were between 20 and 50 years old, have not worked in Singapore previously and stayed in Singapore for less than a year were recruited.

PRIMARY AND SECONDARY OUTCOME MEASURES

Costs, quality-adjusted life-years (QALYs), threshold length of stay, incremental cost-effectiveness ratios (ICERs), cost per active TB case averted.

RESULTS

Of 3584 migrants surveyed, 20.4% had positive interferon-gamma release assay (IGRA) results, with the highest positivity in Filipinos (33.2%). Higher LTBI prevalence was significantly associated with age, marital status and past TB exposure. The cost-effectiveness model projected an ICER of S$57 116 per QALY and S$12 422 per active TB case averted for screening and treating LTBI with 3 months once weekly isoniazid and rifapentine combination regimen treatment compared with no screening over a 50-year time horizon. ICER was most sensitive to the cohort's length of stay in Singapore, yearly disease progression rates from LTBI to active TB, followed by the cost of IGRA testing.

CONCLUSIONS

For LTBI screening and treatment of migrants to be cost-effective, migrants from high burden countries would have to stay in Singapore for ~50 years. Risk-stratified approaches based on projected length of stay and country of origin and/or age group can be considered.

Cost-effectiveness of Latent Tuberculosis Infection Screening before Immigration to Low-Incidence Countries

Prospective migrants to countries where the incidence of tuberculosis (TB) is low (low-incidence countries) receive TB screening; however, screening for latent TB infection (LTBI) before immigration is rare. We evaluated the cost-effectiveness of mandated and sponsored preimmigration LTBI screening for migrants to low-incidence countries. We used discrete event simulation to model preimmigration LTBI screening coupled with postarrival follow-up and treatment for those who test positive. Preimmigration interferon-gamma release assay screening and postarrival rifampin treatment was preferred in deterministic analysis. We calculated cost per quality-adjusted life-year gained for migrants from countries with different TB incidences. Our analysis provides evidence of the cost-effectiveness of preimmigration LTBI screening for migrants to low-incidence countries. Coupled with research on sustainability, acceptability, and program implementation, these results can inform policy decisions.

Using a quality improvement approach to improve care for latent tuberculosis infection

INTRODUCTION

Latent tuberculosis infection (LTBI) management is recognized as a key component of the World Health Organization End Tuberculosis Strategy. The term 'cascade of care in LTBI' has recently been used to refer to the process of LTBI management from identification of persons who may have LTBI to completion of treatment. Large gaps throughout the LTBI cascade of care have been identified. Areas covered: We have reviewed quality improvement (QI) as a potential approach for systematically improving gaps within the LTBI cascade of care. QI principles and approaches were reviewed, as well as the determinants of losses and evidence for solutions (interventions) within the LTBI cascade of care. An example of QI application in LTBI management is described. Expert commentary: Improving LTBI care at the magnitude required to reach the End TB Strategy goals will require systematic and context specific improvements at all steps in the cascade of care in LTBI. A continuous QI approach based on systems thinking, use of locally gathered data, and an iterative learning process can facilitate the process required to make the necessary improvements.

Screening for Latent Tuberculosis Infection in Migrants With CKD: A Cost-effectiveness Analysis

RATIONALE & OBJECTIVE

In countries with a low tuberculosis (TB) incidence, TB disproportionately affects populations born abroad. TB persists in these populations through reactivation of latent TB infection (LTBI) acquired before immigration. Those with chronic kidney disease (CKD) are at increased risk for reactivation and may benefit from LTBI screening and treatment.

STUDY DESIGN

Health administrative data from British Columbia, Canada, were used to inform a cost-effectiveness analysis evaluating LTBI screening in those diagnosed with stage 4 or 5 CKD not requiring dialysis (late-stage CKD) and those who began dialysis therapy.

SETTING & POPULATION

Permanent residents establishing residency in British Columbia, Canada, between 1985 and 2012 who had late-stage CKD diagnosed or began dialysis therapy.

INTERVENTIONS

Screening with the tuberculin skin test or interferon-gamma release assay (IGRA) compared to no LTBI screening at the time of late-stage CKD diagnosis and time of dialysis therapy initiation. Treatment for those who tested positive was isoniazid for 9 months.

OUTCOMES

Costs (2016 Can $), TB cases, and quality-adjusted life-years (QALYs). The incremental cost-effectiveness ratio for QALYs gained was calculated.

MODEL, PERSPECTIVE, & TIMEFRAME

Discrete event simulation model using a health care system perspective, 1.5% discount rate, and 5-year time horizon.

RESULTS

Screening with IGRA was superior to the tuberculin skin test in all situations. Screening with IGRA was less expensive and resulted in better outcomes compared to no screening in those initiating dialysis therapy from countries with an elevated TB incidence. In individuals with late-stage CKD, screening with IGRA was only cost-effective in those 60 years or older (cost per QALY gained, <$48,000) from countries with an elevated TB incidence.

LIMITATIONS

This study has limitations in generalizability to different epidemiologic settings and in modeling complicated clinical decisions.

CONCLUSIONS

LTBI screening should be considered in non-Canadian-born residents initiating dialysis therapy and those with late stage CKD who are older.