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

BackgroundThe majority of tuberculosis in migrants to Canada occurs due to reactivation of latent TB infection. Risk of tuberculosis in those with latent tuberculosis infection can be significantly reduced with treatment. Presently, only 2.4% of new migrants are flagged for post-landing surveillance, which may include latent tuberculosis infection screening; no other migrants receive routine latent tuberculosis infection screening. To aid in reducing the tuberculosis burden in new migrants to Canada, we determined the cost-effectiveness of using different latent tuberculosis infection interventions in migrants under post-arrival surveillance and in all new migrants.MethodsA discrete event simulation model was developed that focused on a Canadian permanent resident cohort after arrival in Canada, utilizing a ten-year time horizon, healthcare system perspective, and 1.5% discount rate. Latent tuberculosis infection interventions were evaluated in the population under surveillance (N = 6100) and the total cohort (N = 260,600). In all evaluations, six different screening and treatment combinations were compared to the base case of tuberculin skin test screening followed by isoniazid treatment only in the population under surveillance. Quality adjusted life years, incident tuberculosis cases, and costs were recorded for each intervention and incremental cost-effectiveness ratios were calculated in relation to the base case.ResultsIn the population under surveillance (N = 6100), using an interferon-gamma release assay followed by rifampin was dominant compared to the base case, preventing 4.90 cases of tuberculosis, a 4.9% reduction, adding 4.0 quality adjusted life years, and saving $353,013 over the ensuing ten-years. Latent tuberculosis infection screening in the total population (N = 260,600) was not cost-effective when compared to the base case, however could potentially prevent 21.8% of incident tuberculosis cases.ConclusionsScreening new migrants under surveillance with an interferon-gamma release assay and treating with rifampin is cost saving, but will not significantly impact TB incidence. Universal latent tuberculosis infection screening and treatment is cost-prohibitive. Research into using risk factors to target screening post-landing may provide alternate solutions.

【背景】赴加拿大移民群体中的绝大多数肺结核病例，源于潜伏性结核感染（latent TB infection）的再激活。针对潜伏性结核感染者，通过治疗可显著降低其罹患肺结核的风险。目前，仅2.4%的新增移民会被纳入入境后监测范畴，该监测流程可能包含潜伏性结核感染筛查；其余移民均未接受常规潜伏性结核感染筛查。为减轻加拿大新增移民群体的肺结核疾病负担，本研究针对入境后监测人群及全体新增移民，评估了不同潜伏性结核感染干预措施的成本效果。【方法】本研究构建了离散事件模拟模型（discrete event simulation model），研究对象为抵达加拿大后的加拿大永久居民队列，研究时限为10年，采用卫生系统视角，贴现率设定为1.5%。研究分别对监测人群（N=6100）及全体队列人群（N=260600）的潜伏性结核感染干预措施进行评估。所有评估均以“仅对监测人群实施结核菌素皮肤试验筛查后给予异烟肼治疗”作为基准方案，将其与6种不同的筛查-治疗组合方案进行对比。记录各干预方案的质量调整生命年（quality adjusted life years）、新发肺结核病例数及相关成本，并计算相对于基准方案的增量成本效果比（incremental cost-effectiveness ratios）。【结果】在监测人群（N=6100）中，采用“γ-干扰素释放试验（interferon-gamma release assay）筛查后给予利福平治疗”的方案相较于基准方案具有绝对优势：可减少4.90例肺结核病例（降幅达4.9%），新增4.0个质量调整生命年，并在后续10年内节省353013加元。对全体队列人群（N=260600）实施潜伏性结核感染筛查的方案，相较于基准方案不具备成本效果，但理论上可减少21.8%的新发肺结核病例。【结论】对入境后监测人群实施γ-干扰素释放试验筛查并给予利福平治疗的方案可节省医疗成本，但无法显著降低肺结核发病率。全民潜伏性结核感染筛查与治疗方案的成本过于高昂，难以承担。未来可探索基于风险因素筛选入境后筛查人群的研究思路，以寻求替代解决方案。