The aim of this study is to evaluate ultra low dose chest computed tomography (ULDCT) for early diagnosis of active tuberculosis in cohort of close contacts of active pulmonary tuberculosis for 1 year follow up

The early diagnosis of active tuberculosis in close contacts have not yet been established. To evaluate the early detection of active pulmonary tuberculosis using ULDCT, the investigators will establish the observational cohort of close contacts living in the same space with active pulmonary tuberculosis. Participants will visit our center at enrollment, after 3 months, and 12 months and will be received ULDCT, chest X-ray and Interferon-gamma assays at each visit. One chest radiologist will interpret findings of ULDCT and chest X-ray.

Patients diagnosed with active tuberculosis will be excluded from the study and treated based on World Health Organization guidelines.

Inclusion Criteria:

• Close contacts of active pulmonary tuberculosis
• Family members of active TB patient who has lived together for more than one month, or work colleagues of active TB patient who has been working in the same office for more than 8 months
• Participants who received explanation of the research plan, understands and writes agreement.

Exclusion Criteria:

• Vulnerable subjects with mental retardation or severe mental illness
• Patients who could not receive chest CT
• Pregnancy
• Close contacts who diagnosed active pulmonary tuberculosis