Diagnostic utility of eosinophils in the pleural fluid. M.A. Mart nez-Garc a, E. CasesViedma, P.J. Cordero-Rodr guez, M. Hidalgo-Ram rez, M. Perpin Äa Â-Tordera, F. SanchisMoret, J.L. Sanchis-Alda Âs. #ERS Journals Ltd 2000. ABSTRACT: This study was conducted to assess the prevalence of eosinophilia in 358 consecutive samples of pleural fluid (all cases corresponded to first thoracentesis), to review the cause of eosinophilic pleural effusions, and to determine whether the presence of eosinophils increases the likelihood of nonmalignant underlying disorders.Eosinophilic pleural effusions were identified in 45 patients (12.6%): malignant underlying conditions were diagnosed in 11 patients (24.4% with eosinophilic effusions) and benign aetiologies were found in 27 patients. Benign aetiologies included uncomplicated paraneumonic effusion in 10 patients, tuberculosis in seven, complicated paraneumonic in five, liver cirrhosis in three, hydronephrosis in one and pulmonary thromboembolism in one. Seven pleural effusions were idiopathic. There was no difference in the prevalence between eosinophilic and noneosinophilic effusions according to the different diagnoses. With parameters of sensitivity, specificity, pretest and post-test probability and positive and negative predictive values for any prevalence figure using the Bayes' theorem and for any value of eosinophils (both in percentage or absolute numbers) in the pleural fluid (receiver operating characteristic curve) an adequate predictor of benign disease was not found.It is concluded that pleural eosinophilia at the initial thoracentesis cannot be considered as a predictor of an underlying benign disorder. Eur Respir J 2000; 15: 166±169. Eosinophilic effusions, defined as $10% eosinophils of the white blood cells [1,2], account for 5±8% of exudative pleural effusions [1,3]. Despite many decades of observation and discussion, the clinical significance and prognostic value of this finding remain controversial. As eosinophilia is a rare finding in malignant pleural effusion, it has been used as an indicator of good prognosis [3,4]. Recent studies, however, have not confirmed a lower prevalence of eosinophilic pleural effusion in malignancies [1,2]. On the other hand, certain conditions are known to frequently produce pleural fluid eosinophilia, such as bloody effusion, pneumothorax, chest trauma, or repeated thoracentesis [5±10]. Also, a high proportion of idiopathic effusions are characterized by pleural fluid eosinophilia, although in most cases data are based on relatively small series of patients [2,3,6,9,11].The aim of this study was to estimate the prevalence of eosinophilia in a large series of pleural effusions, to review the spectrum and frequency of disorders associated with eosinophilic pleural effusions, and to determine whether the presence of eosinophils increases the probability of benign disorder and reduces the likelihood of malignancy. Patients and methodsA retrospective study was made of 385 consecutive samples of pleural fluid collected at th...