title: Multilevel likelihood ratios for identifying exudative pleural effusions(*).
abstract: OBJECTIVE
  To determine multilevel likelihood ratios for pleural fluid tests that are commonly used to discriminate between exudative and transudative pleural effusions.
  
  
  METHODS
  Meta-analysis of patient-level data.
  
  
  METHODS
  Selected studies included patients with diagnoses of exudative or transudative pleural effusions who underwent thoracentesis and laboratory analysis of their pleural fluid.
  
  
  METHODS
  Studies were identified by searching MEDLINE and related bibliographies. Data were obtained for 1,448 patients from seven primary investigators or extracted from dot plots in published reports. Likelihood ratios were calculated from extracted data stratified across ranges of test result values.
  
  
  RESULTS
  Sufficient data were available to calculate multilevel likelihood ratios for the elements of Light's criteria (pleural fluid lactate dehydrogenase [LDH], ratio of pleural fluid to serum LDH, and ratio of pleural fluid to serum protein), pleural fluid protein, ratio of pleural fluid to serum cholesterol, pleural fluid cholesterol, and gradient of pleural fluid to serum albumin. Each of these tests provided levels of likelihood ratios through the most clinically relevant range (0 to 10).
  
  
  CONCLUSIONS
  Multilevel likelihood ratios combined with a clinician's estimation of the pretest probability of an exudative effusion improve the diagnostic accuracy of discriminating between exudative and transudative pleural effusions. Likelihood ratios avoid the use of confusing terms, such as "pseudoexudates," that derive from the use of single cutoff points for pleural fluid tests.
authors.affiliation: Medical University of South Carolina (Drs. Heffner and Sahn), Charleston, SC.
authors.forename: John E
authors.initials: JE
authors.lastname: Heffner
authors.forename: Steven A
authors.initials: SA
authors.lastname: Sahn
authors.forename: Lee K
authors.initials: LK
authors.lastname: Brown
mesh_terms: D003937:Diagnosis, Differential; D005122:Exudates and Transudates; D005260:Female; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D010996:Pleural Effusion / Q000175:diagnosis* / Q000209:etiology