The association of smoking with IGRA and TST results in HIV-1-infected subjects

To assess the association of smoking with the interferon-gamma (IFN-γ) release assay and tuberculin skin test (TST) results in a comparative study on the detection of latent tuberculous infection (LTBI) in human immunodeficiency virus (HIV) 1-infected individuals.

In this cross-sectional study, 305 HIV-1-infected subjects were tested by the QuantiFERON-TB Gold In-Tube assay (QFT-GIT) and the TST. We evaluated the impact of smoking and other LTBI risk factors on QFT-GIT and TST results. RESULTS The concordance of both tests was 93% (κ = 0.71, P < 0.001). The following independent risk factors for both QFT-GIT and TST positivity were identified: birth in a high TB incidence country, self-reported contact with an active TB case and elevated CD4(+) T-cell count (P < 0.001). While smoking was not independently associated with a positive QFT-GIT (OR 1.2, 95%CI 0.5-2.8) or TST result (OR 1.8, 95%CI 0.6-5.9), there was an inverse correlation of the number of cigarettes smoked with IFN-γ levels measured using QFT-GIT (ρ = -0.14, P = 0.027). In addition, smoking was independently associated with a quantitative QFT-GIT response in linear regression analysis (β = 0.129, P = 0.025).

Although smoking may have a minor inhibitory effect on QFT-GIT response, QFT-GIT results seem not to be affected by smoking to a clinically significant extent.