title: Performance of interferon-gamma release assay for tuberculosis screening in inflammatory bowel disease patients.
abstract: BACKGROUND
  Screening for latent tuberculosis (TB) is mandatory in inflammatory bowel disease (IBD) before starting anti-tumor necrosis factor therapy. Data on the utility of screening tests in populations with moderate background risk of TB are limited. This study aims to evaluate the performance of interferon-gamma release assay (IGRA) with QuantiFERON-TB Gold in IBD patients in a TB endemic region.
  
  
  METHODS
  Two hundred sixty-eight consecutive adult IBD patients and 234 healthy controls were prospectively recruited. Detailed clinical history, chest x-ray findings, and IGRA results were documented for all individuals. The IGRA positive rates between IBD patients, with or without immunosuppressant, and healthy controls were compared.
  
  
  RESULTS
  The IGRA result was positive in 21.9% of IBD patients and 19.2% of healthy controls (P = 0.535). IBD patients on immunosuppressive therapy had a significantly lower IGRA positive rate (13.0% versus 29.6%; P = 0.002) compared with immunosuppressant-naive IBD patients. This difference seemed to be most prominent for patients taking azathioprine (11.8% versus 27.3%, P = 0.006).
  
  
  CONCLUSIONS
  IGRA results are negatively impacted by immunosuppressive therapy. Current guidelines suggesting TB screening before anti-tumor necrosis factor therapy may be inadequate in patients already on immunosuppressive drugs. Latent TB testing seems best performed before the initiation of immunosuppressive therapies in IBD patients.
authors.affiliation: *Institute of Digestive Disease, State Key Laboratory of Digestive Diseases, Department of Medicine and Therapeutics, and LKS Institute of Health Science, The Chinese University of Hong Kong, Hong Kong, China; †Department of Microbiology, The Chinese University of Hong Kong, Hong Kong, China; ‡Department of Imaging and Interventional Radiology, Prince of Wales Hospital, Hong Kong, China; and §Division of Infectious Disease, Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Sunny H
authors.initials: SH
authors.lastname: Wong
authors.forename: Margaret
authors.initials: M
authors.lastname: Ip
authors.forename: Whitney
authors.initials: W
authors.lastname: Tang
authors.forename: Zheng
authors.initials: Z
authors.lastname: Lin
authors.forename: Carmen
authors.initials: C
authors.lastname: Kee
authors.forename: Esther
authors.initials: E
authors.lastname: Hung
authors.forename: Grace
authors.initials: G
authors.lastname: Lui
authors.forename: Nelson
authors.initials: N
authors.lastname: Lee
authors.forename: Francis K L
authors.initials: FK
authors.lastname: Chan
authors.forename: Justin C
authors.initials: JC
authors.lastname: Wu
authors.forename: Joseph J Y
authors.initials: JJ
authors.lastname: Sung
authors.forename: Siew C
authors.initials: SC
authors.lastname: Ng
mesh_terms: D000328:Adult; D000998:Antiviral Agents; D016022:Case-Control Studies; D003093:Colitis, Ulcerative / Q000150:complications* / Q000382:microbiology; D003424:Crohn Disease / Q000150:complications* / Q000382:microbiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007371:Interferon-gamma; D059425:Interferon-gamma Release Tests / Q000379:methods*; D055985:Latent Tuberculosis / Q000150:complications / Q000175:diagnosis* / Q000382:microbiology; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D014374:Tuberculin Test / Q000379:methods*
chemical_list: D000998:Antiviral Agents; D007371:Interferon-gamma