Incidence, aetiology and clinical features of eosinophilic pleural effusion: a retrospective study

Eosinophilic pleural effusion (EPE) is a distinct entity among pleural effusions, but its diagnostic and prognostic significance is still controversial. This study aimed to evaluate the incidence and aetiological distribution of EPE in our institution and to assess the relationship between EPE and malignancy and other underlying diseases and the relevance of the percentage of eosinophils and other laboratory parameters.

A retrospective study was conducted by reviewing the medical records of 252 patients with PE from September 2017 to January 2021.

EPE was found in 34 (13.49%) out of 252 patients. There were 20 (58.82%) males and 14 (41.18%) females in the EPE group. The mean percentage of eosinophils in EPE (21.7%, range (10.0-67.5%)) was significantly higher than the percentage of eosinophils in peripheral blood (5.65%, range (0-34.60%); p < 0.05). The most common cause of EPE was malignant disease (52.94%), followed by idiopathy (14.71%), parasites (8.82%), pneumonia (8.82%) and others (14.71%). Comparative analysis of patients with malignant versus nonmalignant EPE showed that patients with malignant EPE were significantly older, and had a lower white blood cell (WBC) count in the pleural fluid (1.8 vs 4.7 cells × 10⁹/L, p < 0.05). However, the percentage of eosinophils in PE was not significantly different between malignant EPE and nonmalignant EPE (p = 0.66). There was no correlation between the percentage of eosinophils in PE and peripheral blood (r = 0.29; p = 0.09).

Malignant disease ranks as the leading cause of EPE. The presence of EPE should not be considered as a predictive factor of benign conditions. Pleural parasitic infestation (PPI) should be emphasized in areas with a high incidence of parasitic disease.