Cost-Effectiveness of LTBI Treatment for TB Contacts in British Columbia

Abstract

Background Contacts of patients with active tuberculosis (“TB contacts”) with a tuberculin skin test (TST) size ≥5 mm are currently recommended treatment for latent TB infection (LTBI). Knowing the cost-effectiveness of LTBI therapy for specific TB contact subpopulations may improve the use of limited resources by reducing the treatment of persons at low TB risk. Objective To evaluate the cost-effectiveness of LTBI therapy for different TB contact populations defined by important risk factors, and to propose an optimal policy based on different recommendation for each subgroup of contacts. Methods A 6-year Markov decision analytic model simulating the quality-adjusted life years (QALYs), number of active TB cases prevented, and costs for hypothetical cohorts of Canadian TB contacts defined by TST size, age group (<10 y/o or above), ethnicity, closeness of contact, and Bacillus Calmette-Guérin (BCG) vaccination status. Results For the majority of subgroups, the current policy of preventive therapy in those with positive TST was the most cost-effective. Nevertheless, our analysis determined that LTBI treatment is not cost-effective in nonhousehold Canadian-born (nonaboriginal) or foreign-born contacts age ≥10 y/o. On the other hand, empirical treatment without screening of all non-BCG-vaccinated household contacts age <10 y/o appeared cost-effective. Such an optimal approach would result in an incremental net monetary benefit of $25 for each contact investigated for a willingness-to-pay of $50,000/QALY. Results were robust to several alternative assumptions considered in sensitivity analyses. Conclusions The current practice of LTBI treatment for TB contacts with a TST size ≥5 mm is cost-effective. A customized approach based on excluding low risk groups from screening and providing treatment to high risk contacts without screening could improve the performance of the program.