Systematic TB screening using WHO radiograph categorisation and care outcomes

BACKGROUND: An appropriate screening approach and quality care are crucial for TB programmes in prisons. This study assessed crude TB prevalence, accuracy of the screening methods and treatment outcomes in a Thai prison. METHOD: This was a retrospective analysis of findings from a mass CXR screening conducted among incarcerated people in July 2017. Digital radiographs were forwarded to a chest physician to read and classify in six categories using WHO categorisation. CXR with significant Categories 3 (no active TB), 4 (not TB), 5 (TB) and 6 (unclassified) abnormalities were eligible for sputum microscopy and Xpert testing. A screening questionnaire locally known as TB-P1 was used for case management. Patients with TB received care in the prison. RESULTS: Of 2,382 prisoners screened, 6.3% had CXR Categories 3-6. Crude prevalence of bacteriologically confirmed TB was 1,133/100,000 (95% CI 748.3-1644.9). The screening´s sensitivity was 96.3% based on CXR Category 5 and 22.2% using TB-P1. Treatment success rates in drug-susceptible and drug-resistant TB patients were respectively 66.7% and 33.3%. CONCLUSION: The WHO radiograph categorisation could be used to screen for TB in the field and may be applied in artificial intelligence for interpreting CXR; screening questionnaires are not effective in prison environments. Nonetheless, low treatment success rates remained a challenge.