Role of interferon-gamma release assays in the diagnosis of pulmonary tuberculosis in patients with advanced HIV infection

BMC Infect Dis. 2010 Mar 20;10:75. doi: 10.1186/1471-2334-10-75.

Abstract

Background: T-cell interferon-gamma release assays (IGRAs) may have a role in the diagnosis of active tuberculosis when evaluating patients for whom standard microbiology has limited sensitivity. Our objective was to examine the accuracy of a commercial IGRA for diagnosis of active tuberculosis in HIV-infected persons.

Methods: We enrolled HIV-infected patients admitted to Mulago Hospital in Kampala, Uganda with cough > or = 2 weeks. All patients underwent standard medical evaluation. We collected peripheral blood specimens at enrollment and performed a commercial, ELISPOT-based IGRA according to the manufacturer's recommendations. IGRA sensitivity and specificity were determined using mycobacterial culture results as the reference standard.

Results: Overall, 236 patients were enrolled. The median CD4+ T-lymphocyte count was 49 cells/microl and 126 (53%) patients were diagnosed with active pulmonary tuberculosis. IGRAs were not performed in 24 (10%) patients due to insufficient mononuclear cell counts. In the remaining 212 patients, results were indeterminate in 54 (25%). IGRAs were positive in 95 of 158 (60%) patients with interpretable results. The proportion of positive test results was similar across CD4+ count strata. IGRA sensitivity was 73% and specificity 54%. IGRA results did not meaningfully alter the probability of active tuberculosis in patients with negative sputum smears.

Conclusions: An ELISPOT-based IGRA detected a high prevalence of latent tuberculosis infection in a hospitalized population of tuberculosis suspects with advanced HIV/AIDS but had limited utility for diagnosis of active tuberculosis in a high prevalence setting. Further research is needed to identify stronger and more specific immune responses in patients with active tuberculosis.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • CD4 Lymphocyte Count
  • Clinical Laboratory Techniques / methods*
  • HIV Infections / complications*
  • HIV Infections / immunology*
  • Humans
  • Interferon-gamma / metabolism*
  • Mycobacterium tuberculosis / isolation & purification
  • Sensitivity and Specificity
  • T-Lymphocytes / immunology*
  • Tuberculosis, Pulmonary / diagnosis*
  • Uganda

Substances

  • Interferon-gamma