Evaluation of pyruvate kinase and oxidative stress parameters in differentiation between transudate and exudate in pleural liquids

Objectives: We aimed to investigate the usability of pleural pyruvate kinase (PK), total antioxidant status (TAS), and total oxidant status (TOS) as an alternative to Light's criteria in exudate-transudate differentiation. Methods: This prospective study was conducted among 84 patients (42 transudates and 42 exudates) with pleural effusion. The levels of PK, TAS, and TOS were measured by using ELISA kits, and the ROC analysis was used to evaluate the diagnostic efficiency. Results: PK (p=0.001), TAS (p=0.027), and TOS (p=0.002) levels in pleural fluids were found to be significantly higher in the exudate group. The cut-off values for PK, TAS, and TOS were 10.64 U/L, 13.54 mmol trolox equivalent/L, and 13.88 mu mol H2O2 equivalent/L, respectively. While the sensitivity values were 97.62 % for PK, 66.67 % for TAS, and 64.29 % for TOS, the specificity values were 80.95 % for PK, 52.38 % for TAS, and 57.14 % for TOS. Conclusions: PK levels in pleural effusion can be useful in suspected cases to differentiate between exudate and transudate in addition to Light's criteria. However, pleural TOS and TAS parameters could not be as sensitive and specific as Light's criteria.