Subclinical tuberculosis disease and its treatment outcomes: a prospective cohort study in South Korea

<b>Introduction:</b> Subclinical tuberculosis (TB) disease is a potential target for public health intervention, because its early identification might reduce TB transmission. We described clinical and laboratory findings and treatment outcomes of subclinical TB disease among patients without human deficiency infection. <b>Methods:</b> We enrolled adult patients with pulmonary TB from the prospective cohort study between 2016 and 2018. Demographic, clinical, and laboratory data were collected from patients. We evaluated treatment outcome in the drug-susceptible cohort, and patient with successful outcome were also followed at least 1 year in order to identify recurrence. <b>Results:</b> Among 420 enrolled patients, 131 (19.2%) patients had with subclinical TB. Multivariate analysis showed that age less than 65 years was the only significant variable associated with subclinical disease. Subclinical disease had significantly lower proportion of acid-fast bacilli smear and culture positivity and multiple lobe involvement compared to active disease. Among 319 patients with treatment success in the drug-susceptible cohort, 6 (1.9%) recurrent cases were identified, and all were patient with active disease. Patients with subclinical disease had higher proportion of favorable outcome; however, its odds ratio was insignificant. <b>Conclusion:</b> Despite its milder clinical presentation, treatment outcome of subclinical TB disease was not significantly different from that of active disease.