Screening for Asymptomatic Tuberculosis among Adults with Household Exposure to a Patient with Pulmonary Tuberculosis.

Background: More than half of tuberculosis (TB) detected by community prevalence surveys is classified as asymptomatic. We evaluated yield of symptom and chest radiograph (CXR) screening of TB-exposed household contacts (HHC) in South Africa. Methods: Adult volunteers (≥18 years) with household exposure to pulmonary TB patients were enrolled at three sites. Systematic screening of TB symptoms (any duration), CXR (any abnormality), and sputum microscopy, Xpert Ultra, and liquid culture were performed. Serum C-reactive protein (CRP) was measured by multiplex bead array. Prevalent TB was microbiologically-confirmed (Xpert Ultra or culture). Symptomatic and asymptomatic TB were defined as prevalent TB with and without reported symptoms, respectively. Results: Between March 2021 - December 2022, 979 HHC were enrolled; 185 (18.9%) living with HIV and 187 (19.1%) with previous TB. Prevalent TB occurred in 51 (5.2%) and was asymptomatic in 42/51 (82.4%). Only 13/42 (31.0%) asymptomatic TB cases were smear-positive [8/13 (61.5%) graded scanty or 1+]. CRP did not discriminate healthy HHC from those with asymptomatic TB (AUC 0.60; 95%CI 0.47-0.73). An abnormal CXR was observed in 23/41 asymptomatic (sensitivity 56.1%, 95%CI 41.0-70.1%) versus 8/9 symptomatic (sensitivity 88.9%, 95%CI 56.5-98.0%) TB cases. Sensitivity of CXR in combination with symptom screening was 64.0% (32/50, 95%CI 50.1-75.9%) for all prevalent TB. Conclusions: More than 80% of confirmed TB cases among HHC were asymptomatic. CXR screening missed more than 40% of these asymptomatic cases. Community prevalence surveys reliant on symptom- and CXR-based approaches may significantly underestimate the prevalence of asymptomatic TB in endemic countries. Funding: Supported by RePORT South Africa through funding from the U.S. National Institutes of Health, CRDF Global, and the South African Medical Research Council. RESEARCH IN CONTEXT: