The Epidemiology of TST Change in Korea

TST will be analyzed in young general population in Korea. Young adults undertake TST as CDC recommendation. Participants with chest radiograph showing active TB lesion are excluded from this study.

Enroll criteria

* A term of whole military conscripts per year in one Reserve Force Battalion * Military conscripts gather from all around area in Korea randomly * Each participant undertake a chest X-ray (CXR) and blood tests including human immunodeficiency virus (HIV) at the start of initiatory training.

Exclusion Criteria

* Chest X-ray suggesting active TB * HIV positive in serology

Design

* After giving informed consent, all participants receive one-step TST following standard procedures. * The largest transverse diameter of induration is measured 48-72hr after injection. * The investigator and these trained nurses were blinded to the status of their demographic characteristics.