Costs of four months of rifampin versus two months of double-dose rifampin for tuberculosis infection: post-hoc analysis of a phase 2b randomized trial

Background Cost is an important consideration when implementing tuberculosis preventive treatment regimens (TPT). We used data from a phase 2b randomized trial of TPT to estimate overall cost and key drivers of costs for two TPT regimens. Methods We did a post-hoc analysis of 915 participants aged ≥10 years who were randomized 1:1 to two rifampin-based regimens: a four-month daily regimen at 10mg/kg (4R10) and a two-month daily regimen at 20mg/kg (2R20; 461 participants). We collected country-specific costs for medications, evaluations, and medical follow-ups from the three participating countries (Canada, Indonesia, and Viet Nam), and converted all costs to 2024 Canadian dollars. We report overall costs of each regimen and cost drivers. Results Overall, 454 participants received 4R10 and 461 participants received 2R20. We found no difference in the cost of 2R20 versus 4R10, with a cost ratio of 0.93 (95%CI 0.79 to 1.07); this was consistent in analyses limited to only those who completed treatment and stratified by country. Costs for medications and the baseline visit accounted for 68%, 49%, and 55% of all costs in Canada, Indonesia, and Viet Nam, respectively. Corresponding costs of routine follow-up visits accounted for approximately 26%, 45%, and 42% of all costs. In all countries, a minority of costs (<10%) were due to additional visits or evaluations not specified in the protocol. Conclusion Most costs associated with TPT are due to medications and the baseline treatment initiation visit. TPT regimens requiring fewer follow-up visits may reduce overall cost, but the magnitude of this reduction varies by country.