Detection of interleukin-2 is not useful for distinguishing between latent and active tuberculosis in clinical practice: a prospective cohort study

Abstract

Objective: Previous reports have identified interleukin-2 (IL-2), quantified in the supernatants of QuantiFERON (R)-TB Gold In-tube (QFT) after 72 h of incubation, as a potential biomarker for distinguishing between latent and active tuberculosis (TB). However, its validity has not been tested in an appropriate clinical cohort.Methods: A multicentre study of 161 consecutive adult patients undergoing evaluation for active TB at eight TB Units in Spain. Interferon-gamma (IFN-gamma) and IL-2 were assessed in the supernatant of QFT after 16 -24 h and 72 h of incubation. The accuracy of IL-2 for indicating latent TB infection (LTBI) was assessed by receiving operating characteristic curves..Results: Twenty-eight participants were not infected, 43 had LTBI, 69 had TB, and 21 were not classifiable. Median (interquartile range) IL-2 concentrations after 72 h of incubation were 0.0 pg/mL (0.0-0.0) in uninfected individuals, 261.0 pg/mL (81.0-853.0) in LTBI individuals, 166.5 pg/mL (33.5-551.5) in patients with extrapulmonary TB, 95.0 pg/mL (26.0-283.0) in patients with smear-negative pulmonary TB, and 38.5 pg/mL (7.5-178.0) in patients with smear-positive pulmonary TB (p