Interferon-gamma release assay versus tuberculin skin test for latent tuberculosis infection among HIV patients in Brazil

Abstract

Setting: Patients HIV+ attending in a reference clinic, Southern Brazil. Objective: To compare the interferon-gamma-release assay (IGRA – QuantiFERON® TB Gold In-Tube) with the tuberculin skin test (TST – PPD-Rt 23) for latent tuberculosis infection (LTBI) in patients with HIV. Design: Cohort study. Patients were simultaneously submitted to the TST and blood collection for the IGRA. Results: A total of 140 subjects were included. Nine (6.4%) were IGRA+/TST+, 12 (8.6%) were IGRA+/TST−, 4 (3%) were IGRA−/TST+, and 115 (82%) IGRA−/TST−. There was poor agreement between tests (kappa = 0.2), and no correlation between these results and CD4+ T lymphocyte counts. During follow-up, one patient with negative results on both tests died from sepsis, and another with discordant results (IGRA+/TST−) exhibited TST seroconversion. Compared to the TST, IGRA showed a sensitivity and specificity of 69% and 90%, respectively. The IGRA detected 8% more positive results than the TST. All patients were followed up for 2 years. Conclusion: The higher accuracy of the IGRA would result in LTBI treatments being administered to patients who would have otherwise been overlooked, decreasing the number of active tuberculosis cases. The long-term survival of HIV carriers requires further evaluation. Keywords: Mycobacterium tuberculosis, Immunological tests, Immunocompromised patients