Diagnostic significance of pleural fluid eosinophilia during initial thoracocentesis

A prospective study of pleural fluid eosinophilia (PFE) during initial thoracocentesis in 162 patients of pleural effusion was undertaken to determine its value in establishing an etiological diagnosis. Eighteen of the 162 cases showed pleural fluid eosinophilia (PFE), twelve could not be labelled with any definitive etiology even after extensive investigations, four belonged to the para-pneumonic group and resolved with treatment. Of the 32 patients with malignancy, PFE was seen in a single case of pleural mesothelioma. None of the patients with tuberculosis, empyema, systemic lupus erythematosus or amoebiasis had PFE. These findings suggest that PFE seen at initial thoracocentesis favours a benign diagnosis, with a rare chance of malignancy. Tuberculosis is unlikely in such patients.