title: Increased oxidative stress in exudative pleural effusions: a new marker for the differentiation between exudates and transudates?
abstract: OBJECTIVE
  Oxidative stress has been associated with various respiratory disorders. We tested the hypothesis that exudates would present higher levels of oxidative stress compared to transudates, expressing the increased local oxidative burst in the former.
  
  
  METHODS
  Prospective, cross-sectional study.
  
  
  METHODS
  One hundred six consecutive patients who had undergone thoracentesis were studied. Ninety patients with a final diagnosis of pleural effusion were further analyzed.
  
  
  METHODS
  The respiratory department and a clinical laboratory of a tertiary hospital.
  
  
  METHODS
  Subjects underwent diagnostic thoracentesis, and standard biochemical parameters (ie, total protein, lactate dehydrogenase, and albumin levels) were measured in pleural fluid and serum. Oxidative stress levels were assessed with a commercially available method (d-ROMs test; Diacron; Grosseto, Italy) that uses conventional Carratelli units (UCarr). In 14 patients, duplicate measurements of oxidative stress and a second thoracentesis were performed on the following day for the assessment of the repeatability of measurements. Receiver operating characteristic (ROC) analysis was performed in order to determine the optimal cutoff level for the differentiation between exudates and transudates.
  
  
  RESULTS
  Oxidative stress levels were higher in exudates compared to transudates (mean [+/- SD] stress level, 274 +/- 72 vs 126 +/- 34 UCarr, respectively; p < 0.0001). No significant differences were found among the levels of oxidative stress in exudative effusions of different etiologies. The area under the ROC curve was 0.992 (95% confidence interval, 0.945 to 0.997), and the method provided high sensitivity (96.8%), high specificity (96.3%), and high accuracy (96.7%) for the diagnosis of exudates at a cutoff level for oxidative stress of 186 UCarr. Consecutive measurements of oxidative stress in the same samples and on fluid from two different thoracenteses performed on 2 consecutive days presented excellent repeatability.
  
  
  CONCLUSIONS
  Oxidative stress levels are higher in exudative pleural effusions compared to transudative effusions, probably due to reactive oxygen species produced in the former.
authors.affiliation: Department of Respiratory Medicine, University of Thessaly, University Hospital of Larissa, Greece.
authors.forename: Evangelia
authors.initials: E
authors.lastname: Papageorgiou
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Kostikas
authors.forename: Theodoros
authors.initials: T
authors.lastname: Kiropoulos
authors.forename: Eleni
authors.initials: E
authors.lastname: Karetsi
authors.forename: Georgios
authors.initials: G
authors.lastname: Mpatavanis
authors.forename: Konstantinos I
authors.initials: KI
authors.lastname: Gourgoulianis
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D005122:Exudates and Transudates / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018384:Oxidative Stress; D010996:Pleural Effusion / Q000378:metabolism*; D011446:Prospective Studies; D012372:ROC Curve