Revisiting Pleural Effusion Classification: Diagnostic Utility of the Serum-Effusion Albumin Gradient Compared with Light’s Criteria

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Introduction: Pleural effusion is a common clinical condition resulting from various systemic or local diseases. Differentiating transudative from exudative effusions is essential for determining etiology and management. Light’s criteria remain the standard diagnostic method; however, their accuracy may decrease in certain conditions, such as in patients receiving diuretic therapy. The Serum–Effusion Albumin Gradient (SEAG) has been proposed as a simpler parameter with potential diagnostic value Objective: To evaluate the diagnostic performance of SEAG in differentiating transudative and exudative pleural effusions using Light’s criteria as the reference standard Methods: This cross-sectional analytic study was conducted at Adam Malik Hospital, Medan, from October to December 2025. Sixty-three patients with pleural effusion undergoing thoracentesis were enrolled consecutively. Statistical analyses included the Mann–Whitney test, Chi-square test, Cohen’s Kappa for agreement, and Receiver Operating Characteristic (ROC) curve analysis to determine the optimal cut-off, sensitivity, and specificity of SEAG Results: Based on Light’s criteria, 58.7% of effusions were classified as exudates and 41.3% as transudates. SEAG classified 60.3% as transudates and 39.7% as exudates. A significant association was found between SEAG and Light’s criteria (χ² = 23.753; p < 0.001) with moderate agreement (κ = 0.571; p < 0.001). ROC analysis showed an AUC of 0.813 (95% CI: 0.704–0.923). The optimal SEAG cut-off was 1.295 g/dL, with 92.3% sensitivity and 73% specificity Conclusion: SEAG demonstrated good diagnostic performance and may serve as an additional parameter in differentiating pleural effusions Keywords: Pleural effusion, SEAG, Light’s criteria, transudate, exudate, quality of care