IL-1RA in the supernatant of QuantiFERON-TB Gold In-Tube and QuantiFERON-TB Gold Plus is useful for discriminating active tuberculosis from latent infection.

Introduction: The new-generation QuantiFERON (QFT)-TB Gold Plus (QFT-Plus) is expected to be useful because it includes a new peptide that is supposed to induce a CD8 T cell response. There is a need for a new marker with sensitivity higher than that of the conventional IFN-γ release assays owing to false-negative results in the latter. This study aimed to compare cytokines in QFT-plus and QuantiFERON-Gold In-Tube (QFT-GIT) supernatants to discriminate between active tuberculosis and latent tuberculosis infection (LTBI).

Methods: A cross-sectional study was conducted at Tokyo National Hospital, wherein 21 LTBI patients and age and sex-matched active TB patients were randomly selected. The levels of various cytokines were measured and compared using the MAGPIX System, and receiver operating characteristic (ROC) curves were generated.

Results: IL-1RA, IFN-γ, CXCL10/IP-10, and CCL4/MIP-1β levels were higher in the active TB group than in the LTBI group in QFT-GIT antigen (GIT Ag) tubes. In QFT-plus tubes, IL-1RA was higher in TB1 and TB2 tubes, while CCL2/MCP-1 was higher only in TB2 tubes. In Nil tubes, CCL5/RANTES, TNF-α, PDGF-BB, and IL-2 levels were significantly higher in the active TB group. IL-1RA in GIT Ag tubes showed the highest area under the curve of 0.8367. The sensitivity and specificity of IL-1RA were 66.7% (95% confidence interval [CI]: 43.0-85.4) and 90.5% (95% CI: 69.6-98.8), respectively, which were the highest among the cytokines.

Conclusions: IL-1RA level in the QFT-GIT supernatant can be a good marker for discriminating active TB from LTBI.