title: A simple laboratory measurement for discrimination of transudative and exudative pleural effusion: pleural viscosity.
abstract: BACKGROUND
  The initial step in establishing the cause of an effusion is to determine whether the fluid is a transudate or exudate. Plasma viscosity is influenced by the concentration of plasma proteins and lipoproteins with the major contribution resulting from fibrinogen. In this study we aimed to evaluate the role of pleural fluid viscosity in discrimination of transudate and exudates.
  
  
  METHODS
  We studied prospectively 63 consecutive patients with pleural effusion in whom diagnostic or therapeutic thoracentesis had been performed. The criteria of Light were applied to differentiate transudates from exudates: 33 patients (23 male, 13 female, mean age=68+/-4 years) had exudates and 30 patients (17 male, 13 female, mean age=68+/-5) had transudates (due to congestive heart failure). Measurements of pleural fluid and plasma viscosity were performed using a viscometer.
  
  
  RESULTS
  There was no statistically significant difference between patients with transudate and exudates in respect to plasma viscosity. However, pleural viscosities of the patients with exudates were significantly higher than those of patients with transudate (1.37+/-0.16 mPa vs 0.93+/-0.03 mPa s p<0.001, respectively). Pleural viscosity has a high sensitivity, specificity (94%, 93%, respectively), positive and negative predictive value (97%, 97%, respectively) for the discrimination of transudative or exudatetive pleural fluid.
  
  
  CONCLUSIONS
  We have demonstrated for the first time that pleural viscosity of the exudative effusion is higher than that of transudative effusion with high sensitivity, specificity, positive and negative predictive value. Regarding the simplicity of this measurement, it may play a valuable role in the accurate and fast discrimination of pleural fluid.
authors.affiliation: Department of Chest Disease, Inonu University School of Medicine, Malatya, Turkey. ozkanyetkin@hotmail.com
authors.forename: Ozkan
authors.initials: O
authors.lastname: Yetkin
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Tek
authors.forename: Akin
authors.initials: A
authors.lastname: Kaya
authors.forename: Aydin
authors.initials: A
authors.lastname: Ciledag
authors.forename: Numan
authors.initials: N
authors.lastname: Numanoglu
mesh_terms: D000368:Aged; D001809:Blood Viscosity; D004812:Epidemiologic Methods; D005122:Exudates and Transudates / Q000502:physiology*; D005260:Female; D006333:Heart Failure / Q000150:complications; D006801:Humans; D008297:Male; D008875:Middle Aged; D010994:Pleura / Q000503:physiopathology; D010996:Pleural Effusion / Q000209:etiology / Q000503:physiopathology*; D016066:Pleural Effusion, Malignant / Q000503:physiopathology; D014783:Viscosity