Diagnostic Value of Carcinoembryonic Antigen and C-reactive Protein Levels in the Discrimination Between Malignant Pleural Effusion and Parapneumonic Effusion

Introduction: There are problems in the differential diagnosis of malignant pleural effusion (MPE) and parapneumonic effusion (PPE). We investigated the diagnostic value of levels of carcinoembryonic antigen (CEA) and C-reactive protein (CRP) in the discrimination of MPE and PPE. Materials and Methods: Twenty-eight patients with MPE and 21 patients with PPE were assessed. CEA and CRP levels were measured in the pleural fluids. Results: CEA levels in the pleural fluid were 55.03±102.96 ng/mL (0.4-387) and 1.11±1.07 ng/mL (0.12-4.30) in patients with MPE and PPE, respectively. The high levels of CEA in patients with MPE were statistically significant (p<0.001). The sensitivity and specificity were 82% and 81%, respectively, when the threshold value for CEA in the pleural fluid was set as 1.45 ng/ mL for the discrimination of MPE from PPE. CRP levels in the pleural fluid were 28.75±23.20 mg/L (1.0-84.9) and 53.74±66.39 mg/L (3.10-248) for patients with MPE and PPE, respectively. The level of CRP in patients with PPE was not statistically significant (p=0.24). The sensitivity and specifity were 61% and 58%, respectively, when the threshold value for CRP in the pleural fluid was set as 28.35 mg/L for the discrimination of PPE from MPE. Conclusion: CEA levels in the pleural fluid were significantly higher in patients with MPE compared to those with PPE. However, the same did not apply for CRP. According to this study, CEA levels in the pleural fluid may be used as an adjunct test for the differential diagnosis of MPE and PPE but CRP is not a good indicator for the discrimination between PPE and MPE.