Accuracy of chest sonography and polymorphonuclear elastase in the assessment of bacterial pleural effusion

Background: The relationship between chest sonography findings and inflammatory markers for assessing bacterial pleural effusion is not well established. We decided to study the accuracy of chest sonography in determining the nature of bacterial pleural effusion and its relationship with polymorphonuclear elastase (PMN-E) results. Methods: Pleural sonography and PMN-E were evaluated in a prospective study of 144 consecutive patients with pleural effusion of various etiologies: 25 complicated parapneumonic, 18 uncomplicated parapneumonic, 33 tuberculous, 17 malignant, 12 transudates, and 39 of unknown etiology. The sonographer distinguished between anechoic and septated pattern. The relationship between sonographic appearance and inflammatory markers was evaluated. Results: All of the complicated parapneumonic, 11 uncomplicated parapneumonic, and 28 tuberculous effusions were septated. Septated pattern and PMN-E value were independent predictors of infectious pleural disease (p <0.05). The simultaneous presence of a septated pattern and a PMN-E higher than 100 microg/l had a sensitivity of 79.1% and a specificity of 91.1% for the diagnosis of bacterial effusions. Conclusions: PMN-E level and the sonographic pattern of pleural fluid may be useful in the diagnosis of bacterial pleural effusions.