Diagnostic accuracy of interleukin 32γ for tuberculous pleural effusion

Accurate diagnosis of tuberculous pleural effusion (TPE) with biomarkers remains difficult. Interleukin 32gamma (IL-32γ) is a recently discovered proinflammatory cytokines which plays a vital role in the immune response to TPE. This study aimed to assess the diagnostic accuracy of IL-32γ for TPE, especially in different ages of patients.

Patients with a confirmed diagnosis of pleural effusion were systematically recruited from Beijing Chao-Yang Hospital between June 2019 and May 2022. The concentration of IL-32γ and interferon-gamma (IFN-γ) were evaluated in the pleural effusions with different etiology from 188 patients using enzyme-linked immunosorbent assay method. Adenosine deaminase (ADA) was determined by peroxidase method.

At a threshold value of 181.56 ng/L, IL-32γ demonstrated an area under the curve (AUC) of 0.812 [95% confidence interval (CI): 0.748-0.865], with sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), positive predictive value (PPV), and negative predictive value (NPV) of 70.2%, 86.0%, 5.0, 0.4, 92.0%, and 55.7%, respectively. In elderly patients (aged >65 years), IL-32γ demonstrated an AUC of 0.984 (95% CI: 0.891-1.000). Notably, the diagnostic accuracy of IL-32γ was significantly higher than that of ADA (P=0.03) and IFN-γ (P=0.02). Similarly, the AUCs for IL-32γ combined with ADA (0.981, 95% CI: 0.886-1.000) and IL-32γ combined with IFN-γ (1.000, 95% CI: 0.920-1.000) were significantly higher than those of ADA (P=0.04) or IFN-γ (P=0.01) alone in elderly patients.

IL-32γ can be used as a valuable biomarker for identifying patients with TPE, especially in elderly patients aged >65 years.