Evaluation of an ultra-portable X-ray system with automated interpretation for tuberculosis active case finding in carceral settings: a diagnostic test accuracy study

Abstract Background The World Health Organization recommends systematic active case finding for tuberculosis (TB) among high-risk populations, including incarcerated individuals; however, many prisons lack screening capacity. In this study, we aimed to evaluate the diagnostic performance of an ultra-portable digital chest radiography system paired with LunitTB, an automated interpretation algorithm, to detect TB disease. Methods We conducted a diagnostic test accuracy study using data collected during a prospective active TB case finding effort TB in a Brazilian prison from February 2023 through May 2024. Eligible individuals included adults (≥18 years) without a history of TB in the past two years. A Fujifilm Digital Radiography (FDR) Xair paired with LunitTB algorithm (version v3.1.5.1) system was used to screen consented individuals for TB disease, irrespective of their TB symptoms. Area under curves (AUC) and 95% confidence intervals (CI) were estimated to determine the accuracy of FDR Xair and LunitTB interpretation when compared to a rigorous microbiologic reference standard. Results We screened a total of 3409 individuals for TB disease as part of our active TB case finding study, and 3399 (99.7%) met our eligibility criteria for the diagnostic test accuracy study. TB prevalence was 4.1% (139/3399, 95%CI: 3.5–4.8%). The AUC for FDR Xair and LunitTB interpretation was 0.89 (95%CI: 0.86–0.93). The accuracy of FDR Xair and LunitTB interpretation among those with any TB symptoms was significantly higher (AUC = 0.93, 95%CI: 0.90–0.97) compared to those without TB symptoms (AUC = 0.87, 95%CI: 0.81–0.92) (DeLong p = 0.033). Conclusions The FDR Xair and LunitTB interpretation enabled us to screen persons deprived of liberty rapidly, with a high diagnostic accuracy particularly among those who reported any TB symptoms.