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

The incidence of inflammatory bowel disease is rising in Hong Kong. Anti-tumor necrosis factor alpha (anti-TNF)-α is effective and increasingly being used for the treatment of patients with refractory disease and complicated disease behaviour. The reactivation of latent tuberculosis (TB) is a well-recognised complication associated with the use of anti-TNF therapy, and most cases occurred in endemic regions. 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. Screening has been shown to reduce the incidence of TB, but it remains unclear whether monitoring during anti-TNF therapy is effective. Despite reported efficacy with the current screening strategy, active TB developed in up to 11.4% of patients receiving anti-TNF therapy. There is therefore an urgent need for better disease monitoring and prevention, particularly in regions where TB is endemic.

Part I of this study aims to investigate the role of IGRA in screening for latent TB in IBD patients and control subjects. Part II of this study is a prospective study 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

Inclusion Criteria:

• patients aged 18 years or older
• patients with a diagnosis of Crohn's disease (CD) or ulcerative colitis (UC) for at least 3 months defined by histology or radiology

Exclusion Criteria:

• Patients with a previous history of TB
• Patients with a positive IGRA or CXR suggesting latent tuberculosis prior to commencement of therapy

Patients attending Prince of Wales Hospital