Routine active case finding in Nigerian penitentiary institutions: comparing yields from digital X-ray with CAD4TB and WHO 4-symptom screening

Correctional centers, including prisons and other penitentiary facilities, are recognized as high-risk environments for tuberculosis (TB) transmission due to overcrowding and limited access to healthcare. In Nigeria, the situation is worsened by infrastructural inadequacies and delays in the judicial process, which contribute to structural risk factors. These conditions heighten the vulnerability of incarcerated individuals to TB and position prisons as potential reservoirs for active transmission. This study compared the screening efficiency and tuberculosis case yield of two screening approaches (digital chest X-ray with computer-aided detection (CAD4TB) and the WHO-recommended four-symptom screen (W4SS)) implemented in penitentiary institutions, with the aim of informing their broader application in similar high-risk settings. TB Screening was carried out in 17 adult correctional centers across 11 states in Nigeria under the USAID-funded TB LON 1&2 project implemented by KNCV Nigeria. With the successful engagement of prison authorities and relevant approvals obtained, healthcare personnel within the facilities received training to support TB screening efforts. Screening procedures were structured through an orderly and stepwise workflow to cover all cells within each institution. Incarcerated individuals were screened using either digital chest X-ray with computer-aided detection (CAD4TB) or the WHO-recommended four-symptom screen (W4SS). Individuals identified as presumptive TB cases had their sputum samples collected and tested. Confirmed TB patients were promptly linked to treatment. Data analysis was done with the TB Screening efficiency cascade and SPSS version 27.0. A total of 26,615 incarcerated individuals were screened between January and August 2022. Among them, 4,162 were identified as presumptive TB (16% yield), and 4,158 underwent evaluation (99.9% evaluation rate). Of the number evaluated, a total of 468 TB cases were confirmed, reflecting an overall TB yield of 11%. Within the intervention period, 456 confirmed TB cases were successfully initiated on treatment (97.4% treatment enrolment rate). Screening with digital X-ray with CAD4TB gave a higher TB yield (17%) compared to W4SS (5%). This was statistically significant. The high yield of TB cases reaffirms the elevated TB burden within correctional settings. The lower Number Needed to Test (NNT) and higher TB yield from digital chest X-ray with CAD4TB underscore its efficiency and effectiveness as a screening tool for such high-burden settings. We recommend routine biannual TB screening in Nigerian penitentiary facilities, utilizing Chest X-ray with CAD4TB.