title: Significance of alpha-2-macroglobulin, alpha-1-acid glycoprotein, and C-reactive protein in pleural effusion differentiation.
abstract: BACKGROUND
  The differentiation between exudates and transudates is fundamental when investigating the cause of pleural effusions. Acute-phase proteins could be potentially useful markers in this discrimination.
  
  
  OBJECTIVE
  The present study was designed to evaluate whether the acute-phase proteins: alpha(2)-macroglobulin (AMG), alpha(1)-acid glycoprotein (AAG) and C-reactive protein (CRP) are useful in investigating the pleural effusions.
  
  
  METHODS
  We prospectively measured the concentrations of the above proteins in the serum and pleural fluid of 84 consecutive patients with various diseases using a nephelometric assay.
  
  
  RESULTS
  Pleural effusion AMG, AAG and CRP were all significantly elevated in the group of patients with exudates compared to patients with transudates (p < 0.001, p < 0.001 and p < 0.01, respectively). An AAG value >63 mg/dl in a pleural effusion is predictive of an exudate with a sensitivity of 90% and a specificity 85%. Similarly, an AMG value >44 mg/dl in a pleural effusion is predictive of an exudate with a sensitivity and a specificity of 90% and 60%, respectively. Moreover, pleural AAG was significantly higher in cancerous exudates than in exudates and transudates of all other cause taken together (p < 0.001). Finally, to differentiate the same pleural effusion, the cut-off value of 1.0 mg/dl of pleural CRP has a sensitivity and a specificity of 74% and 74%, respectively.
  
  
  CONCLUSIONS
  We conclude that both AAG and AMG concentrations in pleural effusions have a high sensitivity and are therefore useful parameters in distinguishing exudates from transudates, but the latter is inferior due to its unacceptably low specificity.
authors.affiliation: Department of Haematology, Medical School University of Crete, Crete, Greece.
authors.forename: M G
authors.initials: MG
authors.lastname: Alexandrakis
authors.forename: S A
authors.initials: SA
authors.lastname: Coulocheri
authors.forename: D
authors.initials: D
authors.lastname: Bouros
authors.forename: I G
authors.initials: IG
authors.lastname: Vlachonikolis
authors.forename: G D
authors.initials: GD
authors.lastname: Eliopoulos
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers; D002097:C-Reactive Protein / Q000032:analysis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009961:Orosomucoid / Q000032:analysis*; D010996:Pleural Effusion / Q000737:chemistry* / Q000175:diagnosis*; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity; D000511:alpha-Macroglobulins / Q000032:analysis*
chemical_list: D015415:Biomarkers; D009961:Orosomucoid; D000511:alpha-Macroglobulins; D002097:C-Reactive Protein