Prevalence, Progression, and Treatment of Asymptomatic Tuberculosis: A Prospective Cohort Study in Lanxi County, Zhejiang Province, China.

Background: Individuals with asymptomatic tuberculosis (TB) are considered a significant risk to the disease burden and transmission. However, the progression and treatment for asymptomatic TB remain incompletely described.

Methods: This prospective cohort study was embedded within a prevalence survey conducted in 2021 and 2022 in Lanxi County, China. All patients with pulmonary TB who consented to participate would be included in the study and were categorized as asymptomatic or symptomatic. For the primary analysis, asymptomatic TB was defined as the absence of current cough, fever, night sweats, weight loss, or hemoptysis. Patients were followed up until 10 November 2024.

Results: Among 109 345 individuals screened, 193 were included, of whom 101 (52.3%) were symptomatic and 92 (47.7%) were asymptomatic. The proportion of asymptomatic TB varied from 32.5% to 62.7% depending on varying symptom negative threshold. Fewer asymptomatic patients were bacteriologically confirmed compared to symptomatic patients (71.7% [66/92] vs 90.1% [91/101], = .001). The median time for asymptomatic patients at screening to develop symptoms was 102 days. Most patients in both groups received treatment for active TB (97.8% vs 99.0%, = .606). The treatment success rate among asymptomatic patients was comparable to that of symptomatic patients (93.3% vs 96.0%, = .521), but their treatment duration was significantly shorter (196 vs 273 days, < .001).

Conclusions: In the community setting, a significant number of TB cases were asymptomatic and remained so for months. These cases demonstrated satisfactory treatment coverage and outcomes, with shorter durations compared to symptomatic TB, suggesting the potential for developing shorter regimens for asymptomatic TB.