Distinguishing tuberculosis from Mycobacterium avium complex disease using an interferon-gamma release assay

Int J Tuberc Lung Dis. 2011 May;15(5):635-40. doi: 10.5588/ijtld.10.0485.


Setting: The QuantiFERON-TB Gold (QFT-G) test can be used to distinguish between tuberculosis (TB) and non-tuberculous mycobacterial disease, but a high background TB infection rate may pose a problem. Although the QuantiFERON-TB (QFT) test, the first-generation QFT-G test, employs a non-specific PPD antigen, avium sensitin is also used as a stimulating antigen.

Objective: To evaluate the utility of these two interferon gamma release assays (IGRAs), QFT-G and QFT, and the tuberculin skin test (TST), to differentiate TB from Mycobacterium avium complex (MAC) disease in an intermediate TB burden country.

Methods: We compared the diagnostic performance of these three tests in 38 prospectively enrolled patients with TB and 40 with MAC lung disease.

Results: The TST yielded positive results in 70.6% of TB and 47.5% of MAC patients; the proportions were respectively 89.5% and 34.3% for QFT-G and 86.8% and 35.3% for QFT. The three tests were of similar accuracy, sensitivity and specificity in diagnosing TB.

Conclusion: Our findings indicate that the TST and IGRAs could not discriminate between active TB and MAC disease or latent TB infection in a TB-endemic area.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Female
  • Humans
  • Interferon-gamma / blood
  • Male
  • Middle Aged
  • Mycobacterium avium Complex / immunology*
  • Mycobacterium avium Complex / isolation & purification
  • Mycobacterium avium-intracellulare Infection / diagnosis*
  • Mycobacterium avium-intracellulare Infection / immunology
  • Mycobacterium tuberculosis / immunology*
  • Mycobacterium tuberculosis / isolation & purification
  • Prospective Studies
  • Sensitivity and Specificity
  • Tuberculin Test / methods
  • Tuberculosis / diagnosis*
  • Tuberculosis / immunology
  • Young Adult


  • Interferon-gamma