Symptom and digital chest X-ray TB screening in South African prisons: Yield and cost-effectiveness

Background : Correctional inmates are at a high risk of tuberculosis (TB). The optimal approach to screening this population is unclear. Methods : We retrospectively reviewed records from TB screening in 64 correctional facilities in South Africa between January 2015 and July 2016. Inmates received symptom screening (any of cough, fever, weight loss, or night sweats) combined with digital chest X-ray (CXR), when available. CXRs were assessed as 'abnormal' or with no abnormalities. Inmates with either a symptom or an 'abnormal' CXR were asked to provide a single spot sputum for Xpert® MTB/RIF testing. We estimated the incremental cost-effectiveness ratio (ICER) per additional TB case detected using CXR screening among asymptomatic inmates. Results : Of 61 580 inmates, CXR screening was available for 41 852. Of these, 19 711 (47.1%) had TB symptoms. Among 22 141 inmates without symptoms, 1939/19 783 (9.8%) had an abnormal CXR, and 8 (1.2%) were Xpert-positive among those with Xpert tests done. Of 14 942 who received symptom screening only and had symptoms, 84% (12 616) had an Xpert result, and 105 (0.8%) were positive. The ICER for CXR screening was US$22 278. Conclusion : Having CXR in addition to symptom screening increased yield but added considerable cost. A major limitation of screening was the low specificity of the symptom screen.