Oxidative Stress Parameters as Biomarkers for Differentiating Exudate and Transudate Pleural Fluid

Classification of pleural fluids as transudate and exudate is important for diagnosis and treatment. Light's criteria are used worldwide to differentiate transudate and exudate. However, in some cases, the distinction between transudate and exudate pleural fluid is unclear. We investigated the serum and pleural fluid TAS, TOS, and OSI values of patients with pleural effusion, and their roles in differentiating transudate and exudate.

Sixty-six patients hospitalized for pleural effusion between July 2018 and December 2020, and 33 healthy individuals, were prospectively analyzed. The patients were divided into exudate and transudate groups according to Light's criteria. Demographic and laboratory data, and serum TAS, TOS, and OSI values, were compared among the three groups (exudate, transudate, and control group). The pleural fluid TAS, TOS, and OSI values were compared between the exudate and transudate groups.

Although the serum TAS value was significantly higher in the control than exudate and transudate groups, the serum TOS and OSI values were significantly lower. There was no significant difference between the exudate and transudate groups in the serum TAS, TOS, or OSI values. Compared to the transudate group, the pleural fluid TAS value was significantly higher in the exudate group, whereas the pleural fluid OSI value was significantly lower. Multivariate logistic regression analysis identified pleural OSI as independent predictors of exudative pleural fluid.

Pleural fluid TAS and OSI values may be useful biomarkers for differentiating exudative and transudative fluid and as an adjunct to Light's criteria in suspicious cases.