Neutrophil elastase alpha 1-proteinase inhibitor complexes in pleural effusions

Polymorphonuclear (PMN) granulocyte derived neutrophil elastase (NE) is rapidly antagonized by alpha 1-proteinase inhibitor (alpha 1 PI) in vivo. To determine the clinical value of elastase alpha 1-proteinase inhibitor complexes (E-alpha 1 PI) in pleural effusions, fluid samples of 99 patients were examined. Fifty-six had malignant effusions, 30 had non-malignant exudates (pleural protein above 3 g/dl) mainly of inflammatory origin, and 13 patients had low protein transudates (below 3 g/dl) due to congestive heart failure. Nonmalignant exudates showed significantly higher (P less than 0.001) concentrations of E-alpha 1 PI compared with malignant effusions or low protein transudates (P less than 0.001). Malignant exudates secondary to lung cancer were characterized by higher (P less than 0.001) median pleural E-alpha 1 PI concentrations compared to malignant exudates due to primarily extrathoracic malignancies. Total pleural leukocyte counts and pleural neutrophil counts were performed in 68 effusions. By this means no clear-cut differentiation between malignant and nonmalignant exudates seems possible except for marked empyema. In conclusion, E-alpha 1 PI complexes in pleural fluid may better reflect the stage of inflammation of pleural effusions rather than mere pleural leukocyte counts. Low levels of E-alpha 1 PI complexes (less than 75 ng/ml) in pleural exudates with protein values above 3 g/dl are characteristic of malignant exudates. Determination of E-alpha 1 PI in pleural exudates may serve as a sensitive marker of inflammation and useful adjunct to pleural cytology in aspects of differential diagnosis of pleural effusions.