Behaviour of nucleated cells in various types of pleural effusion.

INTRODUCTION: To know the behavior of cellular components of pleural fluid can help focus the differential diagnosis of a pleural effusion. Our objective was to assess their composition in different types of pleural effusions and assess whether it provides relevant clinical information.

PATIENTS AND METHODS: Observational, cross-sectional and retrospective study in which the cellular components of pleural effusions of different etiology were analyzed. Pleural effusions were classified as neutrophilic, lymphocytic (≥50% of each one of them), eosinophilic (≥10%) or mesothelial (>5%) and were grouped into six diagnostic categories RESULTS: 1.467 patients were studied (354 heart failure; 59 other transudates; 349 paraneumonic; 133 tuberculous; 397 malignant and 175 other exudates). The predominance cell was lymphocytic in heart failure (44,4%), uncomplicated parapneumonic (29,2%), tuberculosis (88%) and malignant (49,6%); neutrophilic in parapneumonic (57%) and malignant (9,6%); eosinophilic in malignant (6,3%) and mesotelial in tuberculosis (12%). The most frequent etiologies with lymphocyte count ≥80% were tuberculosis (35,1%) and malignant (23,3%). Parameters with higher discriminating accuracy were: leukocytes (transudates: AUC 0,835) and percentage of neutrophils (empyemas: AUC 0,906 and complicated parapneumonic+empyemas: AUC 0,907).

CONCLUSIONS: Nucleated cell counts will help focus the etiology of pleural effusions, since each etiology often have a characteristic cell predominance. The percentage of nucleated cells in pleural fluid not ruled out tuberculosis if there is a high count of mesothelial cells, nor a parapneumonic effusion with lymphocytic predominance, or malignancy with ≥80% lymphocytes.