Incidence and aetiology of eosinophilic pleural effusion

Although eosinophilic pleural effusion (EPE) has been a subject of numerous studies, its clinical significance still remains unclear. The aim of our study was to evaluate: 1) the relative incidence and aetiology of EPE; 2) the predictors of malignancy in patients with EPE; and 3) the relationship between repeated thoracentesis and pleural fluid eosinophilia. A retrospective analysis of 2,205 pleural fluid samples from 1,868 patients treated between 1995 and 2007 was performed. We identified 135 patients with EPE (7.2% of all patients with pleural effusion) and 153 EPE samples. The most common condition associated with EPE was malignancy (34.8%) followed by infectious (19.2%), unknown (14.1%), post-traumatic (8.9%) and miscellaneous (23.0%) pleural effusions. The incidence of malignancy was significantly higher in patients with a lower (< or =40%) pleural fluid eosinophil percentage. 40 patients with EPE underwent a second thoracentesis. In 16, eosinophilia was present in both pleural fluid samples, 14 revealed pleural fluid eosinophilia only after the second thoracentesis and 10 had eosinophilia only in the first pleural fluid sample. Pleural fluid eosinophilia should not be regarded as a predictor of nonmalignant aetiology. Probability of malignancy is lower in effusions with a high eosinophil percentage. The incidence of EPE in patients undergoing second thoracentesis is not different to that found during the first thoracentesis.