Interferon gamma release assay and sputum GeneXpert positivity for tuberculosis burden detection in people deprived of liberty in Brazil: a cross-sectional study.

BACKGROUND

Globally tuberculosis disease (TB) poses a significant public health challenge. People deprived of liberty (PDL) are one of the most affected. This study aims to evaluate the positivity of interferon gamma release assay (IGRA) and molecular sputum testing for TB through a multicenter survey of Brazilian prisons and evaluate factors associated with IGRA positivity.

METHODS

We performed a cross-sectional study among PDL in six male and two female prisons within 6 cities in Brazil in 2025. Eligible participants included consenting adults over 18 years. We randomized 130 individuals per site using prison census for evaluation with a sociodemographic questionnaire, blood testing with QuantiFERON-TB Gold Plus® (IGRA) and sputum testing with GeneXpert Ultra® (Xpert). We included individuals with complete data and valid IGRA results for analysis. Multivariable logistical regression was performed to evaluate factors associated with IGRA positivity stratified by gender.

RESULTS

Among 1040 PDL randomized, 884 were included. The overall IGRA positivity was 53.6% (95% confidence interval [CI] 50.3-56.9) varying between 29.2% (21.6-38.2) and 84.0% (75.3-90.1) among prisons sites, male and female individuals had a positivity of 61.9% (58.1-65.5) and 30.3% (24.7-36.5), respectively. In the multivariable analysis, IGRA positivity was associated with lower education (adjusted odds ratio [aOR] 1.46, 95% CI 1.03-2.07, p = 0.034), previous incarceration (aOR 2.81, 1.85-4.25, p < 0.001), previous TB history (aOR 2.99, 1.39-6.42, p < 0.001) and incarceration time (< 1 year as reference, 3-4 years: aOR 2.15, 1.18-3.92, p = 0.012; 5 years or above: aOR 2.85, 1.66-4.90, p < 0.001) for males. In females, IGRA positivity was associated with previous TB history (aOR 5.93, 1.97-20.2, p = 0.002). One prison could not collect sputum samples; at the remaining sites we detected 20 individuals (2.5%, 20/770) with positive Xpert.

CONCLUSION

Despite variations among prisons and gender, IGRA and Xpert positivity were elevated across sites evaluated in Brazil. These findings underscore the urgent need for systematic and comprehensive tuberculosis screening, prevention, and control strategies in prisons, including the potential evaluation of new preventative technologies such as new TB vaccines.