The role of total oxidative status and total antioxidative status in the differentiation of transüdative and exudative pleural effüsions

Pleural effusions are common problems in clinical practice and their differential diagnosis is frequently problematic. They are generally complications of a systemic pathology or another organ. The aim of the study was to investigate whether total oxidative status (TOS) and/or total anti-oxidative status (TAS) in pleural fluid and serum could be used differentiate between exudates and transudates, and whether oxidative stress has a role in the etiopathogenesis of pleural effusions due to different etiologies.A total of 100 patients with pleural effusion were included. The pleural effusion was transudate in 40 and exudate in 60 of the patients. The pleural effusion was due to benign etiologies in 64 patients while it was due to malignant etiologies in 36 patients.TOS levels in pleural fluid were higher in exudates and malignant effusions compared to those in transudates (6.02±3.31 and 3.79±2.44, respectively, p=0.000) and benign effusions, respectively (6.04±3.26 and 4.61±3.03, respectively, p=0.030). Additionally, oxidative stress index (OSI) in pleural fluid, as an indicator of oxidative stress, was higher in exudates and malignant effusions (1.30±1.90 and 0.45±0.40, respectively, p=0.007) compared to those in transudates and benign effusions, respectively (6.56±19.00 and 0.72±0.97, respectively, p=0.016). For the cut-off value of 4.54 µmol H2O2 equivalent/L pleural TOS had 65% sensitivity and 87% specifity to diagnose exudates. For the cut-off value of 1.13 µmolH2O2 Trolox equivalent/L pleural TAS had 48% sensitivity and 78% specifity to diagnose transudates.Only pleural TOS and OSI levels were found to be significantly different between pleural effusions due to different etiologies. However, these differences were not obvious to use in the differential diagnosis of any specific etiology of pleural effusion.In conclusion, pleural TOS and TAS levels were not as sensitive and specific as Light criteria, however, they can be used in conjunction with Light criteria. On the other hand, higher oxidative stress index levels found in the exudative pleural effusions compared to those in transudative pleural effusions and the lack of a strong correlation between the pleural and the serum levels of these parameters suggest the local production of oxidative stress and this may play a role in the pathogenesis of pleural effusion due to these disease processes.Key words: Pleural effusion, TAS, TOS, Transudate, Exudate