A LONGITUDINAL study conducted in Kampala, Uganda, has revealed that individuals with trace-positive sputum (PWTS) on Xpert Ultra testing face a substantial risk of developing active tuberculosis over 2 years.
Community Screening Reveals Hidden Tuberculosis Risk
From February 2021 to April 2024, researchers screened 31,505 people aged 15 years and older using community events and door-to-door outreach. Participants included 128 PWTS, 139 age- and sex-matched Ultra-negative controls, and 110 more-than-trace positive participants for cross-sectional comparison.
All participants underwent a detailed baseline evaluation, including clinical assessment, repeated sputum testing, and chest x-ray. PWTS and negative-control participants were followed for up to 24 months, with ongoing testing to detect incident TB. Researchers examined the cumulative hazard of TB using both clinician-defined and strictly microbiological criteria, while evaluating whether baseline symptoms or imaging abnormalities predicted disease progression.
High Tuberculosis Risk Despite Minimal Symptoms
Among untreated PWTS participants, the cumulative hazard of tuberculosis was 24% at 1 year and 33% at 2 years, compared with only 3% in negative-control participants. When strict microbiological definitions were applied, the 2-year risk rose to 36% versus 2% in controls. Notably, baseline symptoms, including cough, fever, night sweats, or weight loss, were not predictive of TB development. In contrast, atypical findings on chest x-ray were strongly associated with disease progression, with a hazard ratio of 14.6 (95% CI: 3.3–63.8).
The study highlights that trace-positive sputum results, even when initial evaluations are unremarkable, mark a high-risk group. Patients with both trace-positive sputum and abnormal chest imaging may benefit from early treatment or close monitoring to prevent progression to active TB. These findings support the use of Xpert Ultra as a sensitive tool in community TB screening programmes, enabling targeted interventions for those at greatest risk.
Reference
Sung J et al. Long-term risk of tuberculosis among individuals with Xpert Ultra trace screening results in Uganda: a longitudinal follow-up study. Lancet Respir Med. 2025; DOI:10.1016/S1473-3099(25)00536-5.
