Pleural effusions are generally divided into transudates and exudates. If it is exudative, more diagnostic tests are required in order to determine the cause of the local disease. A malignancy is a common and important cause of exudative pleural effusions. Because the pleural fluid cytology and pleural biopsy specimens do not provide a diagnosis in a high percentage of malignant effusions, several tumor markers have been examined. In order to overcome this limitation, this study hypothesized that C-reactive protein(CRP) and vascular endothelial growth factor(VEGF) measurements would be useful for differentiating trasudates from exudates and determining the differences between a benign and malignant effusion.

Eighty consecutive patients with a pleural effusion (tuberculous 20, parapneumonic 20, malignant 20, transudative 20) were examined prospectively: 60 of them were classified according to Light's criteria as having an exudative fluid and 20 had a transudative fluid. The standard parameters of a pleural effusion were examined and the serum and pleural effusion VEGF levels were measured using enzyme linked immunosorbent assay(ELISA). CRP in the serum and pleural fluid was determined by a turbidimetric immunoassay.

The pleural CRP levels in the exudates were significantly higher than those in the transudates, 4.19±4.22 mg/dl and 1.29±1.45 mg/dl, respectively. The VEGF levels in the pleural effusions were significantly elevated in the exudates compared to the transudate, 1,011±1,055 pg/ml and 389±325 pg/ml, respectively. The VEGF ratio in the exudative effusion is significantly higher than a transudative effusions, 3.9±4.7 and 1.6±0.9, respectively. The pleural CRP levels in the patients with a benign effusion(4.15±4.20 mg/dl) were significantly higher than those in the malignant effusion(1.43±1.91 mg/dl). The VEGF ratio is significantly higher in malignant effusions(4.9±5.5) than in benign effusions(2.8±3.6).

In conclusion, the CRP and VEGF levels in the serum and pleural effusion can distinguish between transudates and exudates. Moreover it can differentiate between benign and malignant pleural effusions.