Diagnostic value of eosinophils in pleural effusion: a prospective study of 26 cases

Eosinophilic pleural effusions (EPFs), defined as the presence of 10% or more eosinophils in the pleural fluid, are relatively rare. Their diagnostic and prognostic significance, however, remains controversial, as most of the studies are based almost entirely on retrospective case studies. This prospective study examines 26 eosinophilic pleural effusions from among 444 consecutive pleural effusions investigated at this tertiary health care center from October 1999 to April 2002. This study was attempted to unravel the diagnostic and prognostic significance of these eosinophilic effusions and assess their clinical implications, if any. Koss and Light's criteria were applied in the analysis, which comprised macroscopic, biochemical, cytological, and microbiological examinations. Of the 26 EPFs studied, five were associated with tuberculosis and three with metastatic disease. Nineteen patients had significant associated lymphocytosis. Twenty-four patients have been followed up and are in good health to date and have had no recurrence of effusion. Thus, EPF could be associated with inflammatory, benign, and malignant conditions. Hence, a closer search for a definite etiological agent is warranted in the setting of such an effusion, especially in populations endemic for tuberculosis, as in a developing country like India and in populations with a high prevalence of malignancy.