The treatment of latent TB with 3HP is an important issue for the prevention of active TB. However, significant proportion of subjects receiving 3HP had adverse reaction. The main purpose of this observation study is to identify subjects who have higher risk to develop adverse reaction. Clinical characteristics and biomarker will be used to predict adverse reaction.

Inclusion Criteria:

• close contact with active TB patients
• patients with autoimmune diseases preceding biological therapy
• health-care workers
• other clinical conditions, which increased the risk of LTBI. LTBI was confirmed by QuantiFERON-TB Gold In-Tube test (QFT-GIT; Qiagen, Valencia, CA, USA) with a cut-off value of 0.35 IU/ml.

Exclusion Criteria:

• age less than 20 years
• pregnant women
• active TB or suspected active TB in the clinical evaluation
• severe liver disease
• ESRD
• organ transplantation
• close contact with a multidrug-resistant TB patient
• obesity (BMI>30 Kgw/m2) and other conditions inappropriate for participation in this study as judged by the investigators.

The newly identified LTBI subjects who wanted to receive LTBI preventive therapy with 3HP were eligible for enrolment.