Diagnostic accuracy cf pleural fluid polymorphonuclear elastase in the differentiation between pyogenic bacterial infectious and non-infectious pleural effusions

Background and Objectives: To establish the diagnostic accuracy of the mark ers of neutrophil activity (elastase and lysozyme) determined in pleural fl uid, for differentiating between pyogenic bacterial infectious and noninfec tious pleural effusions. Patients and Methods: At our tertiary referral tea ching hospital, 160 patients over 14 years with pleural effusion (PE), clas sified as pyogenic bacterial infectious (41 parapneumonic complicated, 32 p arapneumonic non-complicated) and non-infectious (32 neoplasm and 55 undiag nosed pleural exudates) were examined in a prospective study. Polymorphonuc lear elastase (PMN-E) was determined by an immunoactivation method and lyso zyme by a turbidimetric method. Receiver operating characteristic (ROC) cur ves were used to evaluate diagnostic accuracy. Results: Pleural fluid PMN-E was the biochemical marker that best differentiated between pyogenic bacte rial infectious and non-infectious PE, The ROC area under the curve (AUC) f or PMN-E was 0.8276. A PMN-E value over 230 mu g/l diagnosed infectious PE with a specificity of 0.81 and a sensitivity of 0.74. The ROC AUC for prote ins plus lactate dehydrogenase was 0.7430. Differences between the two ROC curves were significant (p = 0.032). After excluding purulent parapneumonic complicated PE, the sensitivity of a pleural fluid PMN-E value equal to or greater than 230 mu g/l was 0.64 and the specificity 0.81. Conclusions: Pl eural fluid PMN-E was the marker that best differentiated infectious from n on-infectious PE, and PMN-E values lower than 230 mu g/l suggest non-infect ious PE. Copyright (C) 2000 S. Karger AG, Basel.