Late Breaking Abstract - Eosinophillic pleural effusion: etiology, management and outcomes – data from the International Multicentre Pleural Research Collaborative

<bold>Introduction:</bold> Data from large multicentre studies on the etiology, management and outcome of eosinophilic pleural effusion (EPE) are lacking. <bold>Aim:</bold> To evaluate the etiology, characteristics, underlying causes, and outcomes of EPE in a diverse international patient cohort. <bold>Methods:</bold> Anonymous data of 226 EPE patients were collected across 7 countries, as part of an ERS clinical research collaboration (International Multicentre Pleural Research Collaborative). <bold>Results:</bold> 210 cases were finally analysed (144 men; median age 66.5 (IQR 55-78) years; median eosinophil proportion in pleural fluid 22% (14-43 %). The most common causes of EPE were malignancy (27.6%), infections (20.4%), post-traumatic events (7.6%), and drug-related reactions (6.2%). 21.9% of cases were classified as EPE of unknown etiology. Median number of investigations needed for diagnosis was 2 (2-3). EPE was managed with drainage (31.9%), repeated thoracentesis (27.1%), specific medications (15.2%), pleurodesis (8.5%) and IPC (3.8%). In 50.7% of patients EPE resolved within a median time of 2 (1-4.5) months. Malignant EPE affected older patients (p=0.0003), was more frequently associated with smoking history (p=0.0004) and pleuritic chest pain (p=0.025) than non-malignant EPE. The percentage of eosinophils in malignant EPE was significantly lower compared to non-malignant EPE (median 18 (13-30)% vs 24 (14-46), p=0.027). Smoking history was a risk factor of malignant etiology in EPE (OR 4.8, 95% CI 1.4 to 16.3). <bold>Conclusions:</bold> This is the first multicentre study providing comprehensive data on the diverse etiology, characteristics, and outcomes of EPE in a large, non-selected patient cohort