Pleural Fluid Amino Acids Contribute to Distinguishing Tuberculosis, Malignant, and Parapneumonic Pleural Effusion Patients.

Background: Differential diagnosis of pleural effusions poses a considerable challenge in clinical practice. In this study, we explored biomarkers in pleural fluid for distinguishing tuberculosis, malignant, and parapneumonic pleural effusion patients.

Methods: A total of 166 patients with exudative pleural effusion were collected, including 86 patients with tuberculosis pleural effusion (TPE), 52 patients with malignant pleural effusion (MPE), and 28 patients with parapneumonic effusion (PE). Hydrogen nuclear magnetic resonance (1HNMR) based metabolomics and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS) were employed to analyze the pleural fluid.

Results: There were significant differences in the levels of bile acid, leucine, citrulline, pyruvate, betaine, and taurine in the pleural effusion of the three groups (p < 0.05) by 1HNMR, indicating significant changes in amino acid metabolism among groups. Twelve amino acids in pleural effusion were further quantitatively determined by UPLC-MS. The results showed that arginine could be used to distinguish MPE from PE and TPE with the area under the ROC curve (AUC) value of 0.87, and lysine could distinguish PE from TPE with the AUC value of 0.74.

Conclusions: Pleural fluid arginine could be used as a potential biomarker for distinguishing MPE from PE and TPE, and lysine could be used for distinguishing PE from TPE, which is worthy of further study.