title: Improving the predictive accuracy of identifying exudative effusions.
abstract: BACKGROUND
  Application of Light's criteria results in misclassification of some transudative effusions as exudative, particularly because of congestive heart failure (CHF). We sought to determine if the serum to pleural fluid albumin (SF-A) and serum to pleural fluid protein (SF-P) gradients increased the predictive accuracy to correctly identify exudative effusions.
  
  
  METHODS
  We retrospectively analyzed 1,153 consecutive patients who underwent a diagnostic thoracentesis at the Medical University South Carolina. Univariable logistic regression analyses were used to determine the statistical significance of pleural fluid tests that correctly identified exudative effusions. Tests with significant diagnostic accuracy were combined in multivariable logistic regression models, with calculation of areas under the curve (AUCs) to determine their predictive accuracy. The predictive capability of the best model was compared with Light's criteria and other test combinations.
  
  
  RESULTS
  Pleural fluid lactate dehydrogenase (LDH), SF-A gradient, and SF-P gradient had a significant effect on the probability of identifying exudative pleural effusions. When combined together in a multivariable logistic regression, LDH (OR, 14.09 [95% CI, 2.25-85.50]), SF-A gradient (OR, 7.16 [95% CI, 1.24-41.43]), and SF-P gradient (OR, 6.83 [95% CI, 1.56-27.88]) had an AUC of 0.92 (95% CI, 0.85-0.98).
  
  
  CONCLUSIONS
  Application of Light's criteria, not uncommonly, misclassifies CHF transudative effusions as exudates. In cases where no cause for an exudative effusion can be identified or CHF is suspected, the sequential application of the fluid LDH, followed by the SF-P and then the SF-A gradients, may assist in reclassifying pleural effusions as transudates.
authors.affiliation: Division of Pulmonary, Critical Care, Allergy, and Sleep Medicine.
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Kummerfeldt
authors.affiliation: Department of Public Health Sciences, Medical University of South Carolina, Charleston, SC.
authors.forename: Cody C
authors.initials: CC
authors.lastname: Chiuzan
authors.affiliation: Division of Pulmonary, Critical Care, Allergy, and Sleep Medicine. Electronic address: hugginjt@musc.edu.
authors.forename: John T
authors.initials: JT
authors.lastname: Huggins
authors.affiliation: Division of Pulmonary, Critical Care, Allergy, and Sleep Medicine.
authors.forename: Matthew L
authors.initials: ML
authors.lastname: DiVietro
authors.affiliation: Division of Pulmonary, Critical Care, Allergy, and Sleep Medicine.
authors.forename: Jennings E
authors.initials: JE
authors.lastname: Nestor
authors.affiliation: Division of Pulmonary, Critical Care, Allergy, and Sleep Medicine.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Sahn
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Albany Medical College, Albany, NY.
authors.forename: Peter
authors.initials: P
authors.lastname: Doelken
mesh_terms: D000418:Albumins / Q000032:analysis; D003937:Diagnosis, Differential; D005260:Female; D006333:Heart Failure / Q000150:complications*; D006801:Humans; D006836:Hydro-Lyases / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D010996:Pleural Effusion / Q000175:diagnosis* / Q000209:etiology / Q000378:metabolism; D011506:Proteins / Q000032:analysis*; D015203:Reproducibility of Results; D012189:Retrospective Studies
chemical_list: D000418:Albumins; D011506:Proteins; D006836:Hydro-Lyases; C045581:lactate dehydratase