Incidence of tuberculosis infection and active tuberculosis among incarcerated individuals in Antananarivo, Madagascar

Abstract Background Tuberculosis significantly affects high-risk populations such as prisoners. This study investigated the incidence of tuberculosis infection (TBI) and its progression to active tuberculosis (TB) in the central prison in Antananarivo, Madagascar. Methods A prospective study was conducted among 297 inmates between September 2021 and July 2023. Baseline assessments included socio-demographic data, medical history, and TBI screening using QuantiFERON TB GOLD PLUS (QFT-G). Participants were categorized based on TBI status (QFT-G positive or negative and no signs of tuberculosis disease), followed for 12 months and monitored for active TB. The incidence of TBI and TB was calculated. Kaplan‒Meier curves were used to compare TB–free survival probabilities by TBI status. Cox regression models were fitted to analyse baseline characteristics associated with TB. Results The overall TB incidence rate was 50.8 cases per 1000 person-years, which is notably higher than the national average. Participants with TBI at baseline experienced a significantly higher incidence of active TB (74.8 cases per 1000 person-years) compared to those who tested negative (15.7 cases per 1000 person-years). Factors associated with TB were a history of TB treatment and abnormal body mass index (underweight and overweight). The incidence of TBI during follow-up was 572.4 cases per 1000 person-years. Conclusions In this high-TB-burden country, the incidence of TB was remarkably high among incarcerated individuals, particularly among those with TBI. TBI testing is desirable in prisons to identify the highest-risk individuals and to implement TB prevention measures.