title: Does an interferon-gamma release assay change practice in possible latent tuberculosis?
abstract: OBJECTIVE
  Suspected latent tuberculosis infection (LTBI) is a common reason for referral to TB clinics. Interferon-gamma release assays (IGRAs) are more specific than tuberculin skin tests (TSTs) for diagnosing LTBI. The aim of this study is to determine if IGRA changes practice in the management of cases referred to a TB clinic for possible LTBI.
  
  
  METHODS
  A prospective study was performed over 29 months. All adult patients who had TST, CXR & IGRA were included. The original decision regarding TB chemoprophylaxis was made by TB team consensus, based on clinical history and TST. Cases were then analysed with the addition of IGRA to determine if this had altered management. An independent physician subsequently reviewed the cases.
  
  
  RESULTS
  Of 204 patients studied, 68 were immunocompromised. 120 patients had positive TSTs. Of these, 36 (30%) had a positive QFT and 84 (70%) had a negative QFT. Practice changed in 78 (65%) cases with positive TST, all avoiding TB chemoprophylaxis due to QFT. Of the immunocompromised patients, 17 (25%) underwent change of practice. No cases of active TB have developed.
  
  
  CONCLUSIONS
  This study demonstrates a significant change of clinical practice due to IGRA use. Our findings support the NICE 2011 recommendations.
authors.affiliation: Department of Respiratory Medicine and TB Clinic, Royal Infirmary of Edinburgh, 51 Little France Crescent, Edinburgh, Midlothian EH16 4SA, UK. james.tiernan@nhs.net
authors.forename: J F
authors.initials: JF
authors.lastname: Tiernan
authors.forename: S
authors.initials: S
authors.lastname: Gilhooley
authors.forename: M E
authors.initials: ME
authors.lastname: Jones
authors.forename: J D
authors.initials: JD
authors.lastname: Chalmers
authors.forename: C
authors.initials: C
authors.lastname: McSparron
authors.forename: I F
authors.initials: IF
authors.lastname: Laurenson
authors.forename: A T
authors.initials: AT
authors.lastname: Hill
mesh_terms: D000328:Adult; D000995:Antitubercular Agents / Q000627:therapeutic use; D018450:Disease Progression; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D059425:Interferon-gamma Release Tests / Q000379:methods; D007538:Isoniazid / Q000627:therapeutic use; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000276:immunology; D008297:Male; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D017410:Practice Guidelines as Topic; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012017:Referral and Consultation; D015203:Reproducibility of Results; D012293:Rifampin / Q000627:therapeutic use; D018570:Risk Assessment; D012606:Scotland / Q000453:epidemiology; D012680:Sensitivity and Specificity; D014374:Tuberculin Test / Q000379:methods*
chemical_list: D000995:Antitubercular Agents; D007538:Isoniazid; D012293:Rifampin