[Tuberculosis Risk and Efficacy of Latent Tuberculosis Infection Treatment among Participants of National Latent...

The study aim was to investigate the natural history of latent tuberculosis infection (LTBI) and the efficacy of LTBI treatment among participants in the national LTBI screening program. Individuals who underwent an interferon-gamma release assay (IGRA) between 2017 and 2020 were included, and tuberculosis (TB) development was investigated until April 2021. Cox proportional hazards models were used to investigate the risk factors affecting TB incidence among IGRA-negative and IGRA-positive individuals who did not undergo treatment. Additionally, the numbers needed to treat (NNT), stratified by age and interferon levels, were calculated among IGRA-positive individuals who did not undergo treatment and those who completed treatment. A comparison with contacts enrolled within the same period was performed. A total of 1,120,948 participants were included and 798 TB cases were identified. After adjusting for age, sex, history of TB exposure, and high-risk TB conditions, higher interferon levels were associated with a higher risk of TB incidence. This trend was particularly prominent in younger age groups; it was not observed in older age groups. The tendency toward a lower NNT among younger IGRA-positive individuals with higher interferon levels was observed among participants of the national screening program and contacts. Overall, a higher NNT was observed among participants of the national screening program than among contacts. However, among study participants with higher interferon levels who were under the age of 35 years, an NNT comparable to that of contacts was observed. Stratifying TB risk according to age and interferon levels could lead to more efficient LTBI screening and treatment on a national scale. Further research is warranted to validate this strategy.