title: Interferon-gamma release assay performance in pulmonary and extrapulmonary tuberculosis.
abstract: BACKGROUND
  The diagnosis of tuberculosis remains difficult. This study aimed to assess performance of interferon-gamma release assay (IGRA) in diagnosis of active tuberculosis (ATB) with pulmonary and extrapulmonary involvements, and to determine the diagnostic role of IGRA (T-SPOT.TB) and tuberculin skin test (TST) in BCG-vaccinated population.
  
  
  RESULTS
  Two hundred twenty-six ATB suspects were recruited and examined with T-SPOT.TB. Among them, fifty-two and seventy-six subjects were simultaneously tested by TST with 5TU or 1TU of purified protein derivative (PPD). The sensitivity of T-SPOT.TB was 94.7% (71/75), comparable in pulmonary and extrapulmonary disease groups (95.6% vs. 93.3%, P>0.05), while the specificity was 84.10% (90/107) but differed in two groups (69.2% vs. 88.9%, P = 0.02). Compared to T-SPOT.TB, TST with 5TU-PPD showed less sensitivity (92.3% vs. 56.4%) and specificity (84.6% vs. 61.5%) (both P<0.01); the sensitivity of TST with 1TU-PPD was 27.8%, and despite its specificity identical to T-SPOT.TB (both 82.8%) positive predictive value (PPV) was only 33.3%. By combining T-SPOT.TB with TST (1TU), the specificity rose to 95%, but the PPV stayed unchanged.
  
  
  CONCLUSIONS
  IGRA could function as a powerful immunodiagnostic test to explore pulmonary and extrapulmonary TB, while TST failed to play a reliable or auxiliary role in identifying TB disease and infection in the BCG-vaccinated population.
authors.affiliation: Department of Infectious Diseases, Huashan Hospital, Fudan University, Shanghai, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Feng
authors.forename: Ni
authors.initials: N
authors.lastname: Diao
authors.forename: Lingyun
authors.initials: L
authors.lastname: Shao
authors.forename: Jing
authors.initials: J
authors.lastname: Wu
authors.forename: Shu
authors.initials: S
authors.lastname: Zhang
authors.forename: Jialin
authors.initials: J
authors.lastname: Jin
authors.forename: Feifei
authors.initials: F
authors.lastname: Wang
authors.forename: Xinhua
authors.initials: X
authors.lastname: Weng
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.forename: Wenhong
authors.initials: W
authors.lastname: Zhang
mesh_terms: D001500:BCG Vaccine; D003937:Diagnosis, Differential; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism*; D059425:Interferon-gamma Release Tests / Q000379:methods*; D016013:Likelihood Functions; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D014373:Tuberculin; D014374:Tuberculin Test / Q000379:methods; D014376:Tuberculosis / Q000175:diagnosis* / Q000276:immunology; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000276:immunology
chemical_list: D001500:BCG Vaccine; D014373:Tuberculin; D007371:Interferon-gamma