Background & Objectives : One of the first steps in diagnosis of pleural effusion is distinction between exudative and transudative types. The aim of this study was to assess C – reactive protein (CRP) level as one of the diagnostic marker for differentiation of exudative from transudative pleural effusions.

  Methods : In this descriptive and sectional study, 80 patients with confirmed pleural effusion were assessed. These patients were divided into two groups based on Light´s criteria. Serum and pleural CRP were measured with Latex Agglutination Test.

  Results : Out of 80 patients with pleural effusion 26 were transudative (32.5%) and 54 were exudative (67.5%). In exudative group, 72.2% of cases were CRP positive (1+ to 3+), and in transudative group, only 38.5% of cases were CRP positive (p < 0.05). There was no significant differences between different exudative pleural effusion etiologies (infectious and non infectious, malignant and non malignant and tuberculosis) and the number of CRP positive cases (p > 0.05). The rate of CRP positivity in exudative pleural effusion group was more than transudative group (p < 0.05).

  Conclusion: According to our study it seems that CRP criterion could help in distinction between exudative and transudative types of pleural effusion.