Combined carcinoembryonic antigen, carbohydrate antigen 50, and neutrophil gelatinase-associated lipocalin distinguish benign and malignant pleural effusions: a Bayesian analysis

The value of pleural fluid neutrophil gelatinase-associated lipocalin (NGAL) in distinguishing malignant (MPE) and benign pleural effusions (BPE) remains unclear. This study aimed to evaluate the diagnostic accuracy of pleural fluid NGAL in differentiating MPE from BPE. We prospectively enrolled patients presenting with undiagnosed pleural effusion at the Affiliated Hospital of Inner Mongolia Medical University between September 2018 and July 2021. Their pleural fluid NGAL levels were measured using a Luminex platform. Receiver operating characteristic (ROC) curve analysis was used to assess the diagnostic performance of NGAL, carcinoembryonic antigen (CEA), and carbohydrate antigen 50 (CA50) for MPE. Bayesian likelihood ratio analysis was employed to calculate each biomarker's likelihood ratios (LRs). A total of 153 participants were included, comprising 66 cases with MPE and 87 cases with BPE. Pleural fluid NGAL levels were significantly higher in MPE than in BPE. The area under the ROC curve (AUC) of NGAL for diagnosing MPE was 0.72 (95% CI: 0.63-0.80). When combined with CEA and CA50, the AUC increased to 0.88 (95% CI: 0.82-0.94), with a sensitivity of 0.82 (0.70-0.90) and specificity of 0.87 (0.79-0.94). The posterior probability of MPE based on the combined use of the three biomarkers was 0.967. Pleural fluid NGAL demonstrates moderate diagnostic performance for MPE and can serve as an auxiliary biomarker in clinical practice. The combination of NGAL, CEA, and CA50 represents a useful diagnostic tool for MPE.