Hong Kong is a region of intermediate TB burden, and the reactivation of latent TB in IMID patients treated with anti-TNF can be a serious problem. This study aims to investigate the role of IGRA in screening for latent TB in IBD patients and control subjects. In part II of the study, patients of other immune-mediated inflammatory diseases (IMID) will also be included to investigate the role of serial interferon-gamma release assays (IGRA) for the diagnosis of tuberculosis (TB) infection in patients with immune-mediated inflammatory diseases (IMID) treated with biologics