The Diagnostic Value of Interleukin-2 and Interferon-γ Induced by Fusion Protein (ESAT-6/CFP-10/Rv1985c) for Active Mycobacterium tuberculosis Infection

Objective This study aimed to evaluate the diagnostic ability of interleukin 2 (IL-2) and interferon gamma (IFN-γ) release assay induced by the fusion protein (ESAT-6/CFP-10/Rv1985c) for detecting active tuberculosis (ATB) in clinically visiting patients. Methods A total of 970 subjects (215 in ATB group and 755 in non-ATB group) underwent both an interferon-γ release assay (IGRA) and a TB-DNA PCR assay. Using clinical diagnosis as the gold standard, both qualitative and quantitative test results for IL-2 and IFN-γ were analyzed. Subsequently, the diagnostic ability of IL-2 and IFN-γ to screen for ATB among the high-risk population was then evaluated. Results IL-2 exhibited higher specificity, while IFN-γ demonstrated higher sensitivity in distinguishing between ATB and non-ATB subjects. The sensitivity of the serial application of IL-2 and IFN-γ had no significant difference (p = 1.000) compared with IFN-γ; the specificity of the serial application of IL-2 and IFN-γ had no significant difference (p = 0.708) compared with IL-2. Quantitative analysis of the results revealed that the IL-2 and IFN-γ values were significantly higher in the ATB group compared with the non-ATB group. Additionally, the combined predictors of IL-2 and IFN-γ did not show a significant difference compared with IL-2 alone (p = 0.324) or IFN-γ alone (p = 0.405). Conclusions This study demonstrated that IL-2 and IFN-γ release assays induced by the fusion protein (ESAT-6/CFP-10/Rv1985c) were valuable for distinguishing ATB from non-ATB subjects, with IL-2 exhibiting higher specificity and IFN-γ demonstrating higher sensitivity.