Usefulness of the combined IFN-γ and IL-2 release test in distinguishing between pulmonary tuberculosis and non-pulmonary tuberculosis.

[BACKGROUND] Pulmonary tuberculosis (PTB) is a lung-specific disease caused by (MTB) infection. Its clinical symptoms and imaging features are non-specific, often leading to misdiagnosis. Therefore, rapid, accurate and low-cost diagnostic methods are crucial for distinguishing PTB from other pulmonary conditions. The interferon-gamma (IFN-γ) release assays is an immunological diagnostic tool with proven value in detecting tuberculosis (TB) infection; however, its specificity in assisting the diagnosis of active TB remains limited. The combined IFN-γ and interleukin-2 (IL-2) release test, targeting MTB-specific cytokines, represents an improvement over traditional IFN-γ release assays, offering increased diagnostic specificity through the simultaneous assessment of multiple cytokine responses. This study aimed to evaluate the diagnostic value of the combined IFN-γ and IL-2 release test in differentiating PTB from other lung diseases.

[METHODS] A retrospective cohort study was conducted involving 309 patients hospitalized in the Respiratory Department of Fuyang People’s Hospital from July 2022 to February 2024. Among the 103 patients with PTB, 78 cases were pathogen confirmed PTB, and 25 cases were Clinically diagnosed PTB, and 206 patients had other lung diseases. Cytokine levels were measured using enzyme-linked immunosorbent assay (ELISA). Data analysis was performed with SPSS 26.0 and Graphpad Prism 9.0 software.

[RESULTS] The sensitivity of the combined IFN-γ and IL-2 release test for diagnosing PTB was 85.4%, with a specificity of 85.0% and an area under the curve (AUC) of 0.942. Specificity differed according to disease type, with 80.4% for pneumonia, greater than 90% for lung cancer, (NTM) lung disease, and chronic obstructive pulmonary disease (COPD), and above 80% for bronchitis. Notably, the double-positive specificity reached 95.6% for other lung diseases.

[CONCLUSION] The MTB-specific combined IFN-γ and IL-2 release test demonstrates high sensitivity and specificity, providing valuable diagnostic support for distinguishing PTB from other pulmonary diseases, and holds significant clinical value for identifying PTB.

[CLINICAL TRAIL NUMBER] Not applicable.