Effects of Light’s criteria on the diagnostic accuracy of pleural fluid carcinoembryonic antigen concentrations for malignant pleural effusion

The pleural fluid carcinoembryonic antigen (CEA) test is a diagnostic tool for malignant pleural effusion (MPE). Light's criteria are an important method for the differential diagnosis of pleural effusion. This study aimed to analyze the effects of Light's criteria on the diagnostic accuracy of CEA concentrations. The subjects of this study were from a retrospective cohort (BUFF study) and a prospective cohort (SIMPLE study). All participants had pleural effusion with undetermined cause. We extracted data on the basic clinical characteristics, final diagnoses, and pleural fluid CEA concentrations of the patients from their medical records. Spearman correlation analysis was used to explore the correlations between CEA concentrations and serum, lactate dehydrogenase (LDH), and total protein levels in the pleural fluid. Logistic regression analysis was used to investigate the relationship between Light's criteria and false-negative CEA results. A total of 340 patients with pleural effusion of unknown etiology were included in this study, including 118 patients with MPE patients and 222 patients with benign pleural effusion (BPE). In all patients, as well as in those with BPE or MPE, the pleural fluid CEA concentration was positively correlated with the total protein ratio, the LDH ratio, and pleural fluid LDH activity, with correlation coefficients of approximately 0.3. In patients with negative CEA results, an LDH ratio greater than 0.6 was independently associated with false-negative CEA results. In patients with negative pleural fluid CEA results, an LDH ratio greater than 0.6 suggests a false-negative result.