A prospective cohort study of latent tuberculosis in adult close contacts of active pulmonary tuberculosis patients in Korea

Background/Aims: The objective of this prospective study was to evaluate the diagnosis and treatment of latent tuberculosis infection (LTBI) in adult close contacts of active pulmonary tuberculosis (TB) patients in Korea. Methods: Adult close contacts of active pulmonary TB patients were recruited at a regional tertiary hospital in Korea. The participants were tested for LTBI using the tuberculin skin test (TST) and/or QuantiFERON-TB Gold (QFT-G) test. LTBI patients, who consented to treatment, were randomly assigned to receive isoniazid for 9 months (9INH) or rifampin for 4 months (4RIF). Results: We examined 189 adult close contacts (> 18 years) of 107 active pulmonary TB patients. The TST and QFT-G were positive (${\geq}10mm$) in 75/183 (39.7%) and 45/118 (38.1%) tested participants, respectively. Among 88 TST or QFT-G positive LTBI participants, 45 participants were randomly assigned to receive 4RIF (n = 21) or 9INH (n = 24), respectively. The average treatment duration for the 4RIF and 9INH groups was $3.3{\pm}1.3$ and $6.1{\pm}2.7months$, respectively. Treatment was completed in 25 participants (4RIF, n = 16; 9INH, n = 9). LTBI participants who accepted treatment were more likely to be women and have more cavitary lesions on the chest radiographs of index cases and positive TST and QFT-G results compared to those who refused treatment. Conclusions: About 40% of adult close contacts of active pulmonary TB patients had LTBI; about 50% of these LTBI participants agreed to treatment.