A new method for active tuberculosis case finding

点击翻译按钮获取中文摘要

PROJECT SUMMARY A critical component of the 2035 End TB Strategy is development of improved methods for Active Case Finding (ACF) of previously undiagnosed TB disease. Most ACF conducted by national tuberculosis control programs is based on testing household contacts (HCs) of remotely-acquired but newly-diagnosed cases of TB disease. This approach typically detects previously undiagnosed TB disease in 2-4% of HCs. We propose to test an entirely new method of ACF based on testing HCs of adolescents with recently-acquired and newly-diagnosed TB infection. This innovative method of ACF has the advantage that, since infections were recently acquired, the source cases are likely still among the close contacts of the new IGRA convertor. For this reason, we hypothesize that a source case will be found for as many as 50% of these new convertors. This approach is based on results of our recent 3-year study of serial testing for TB infection among 650 adolescent schoolchildren in Tanzania. The study was based on annual testing for TB infection using an interferon gamma release assay (IGRA). We showed that such testing was feasible and detected a 2.9% annual rate of infection. In the proposed new 5-year study we will perform baseline IGRA testing on 1200 Tanzanian adolescents followed by Q4 month IGRA testing x4 on the estimated 1020 who are IGRA negative at baseline. We anticipate detecting new TB infection (IGRA conversion to positive) in 50 participants. We will then test 200 of their household and other close contacts (collectively, their close contacts, CC) and predict that we will identify a source case of previously undiagnosed TB in a minimum of 25 or 50% of these 50 new adolescent infections. The predicted rate of new TB disease detection among CCs is therefore 25/200 or 12.5%, which is 3-6 times higher than the current approach for testing HCs of patients with TB disease. Cost-effectiveness will be analyzed and compared to the current approach used by the National Program on Tuberculosis and Leprosy. Successful completion of the proposed study with the hypothesized outcomes has the potential for a major impact on global tuberculosis outcomes. It is expected that the numerous new point-of-care IGRA tests under development will make serial testing feasible and economical at a programmatic level in low income countries. The research study will be conducted with the comprehensive DarDar Research Program, a 20-year research collaboration between Muhimbili University of Health and Allied Sciences (MUHAS, Tanzania) and the Geisel School of Medicine at Dartmouth (USA) and will include two consultant epidemiologists with extensive experience in evaluating TB control programs (Horsburgh, Whalen).