Serum and pleural fluid N-Terminal-Pro-B-Type natriuretic peptide concentrations in the differential diagnosis of pleural effusions

Currently, new biomarkers like N-Terminal-Pro-B-Type natriuretic peptide (NT-proBNP) have been used in the differential diagnosis of pleural effusions. In our study, we aimed to investigate the diagnostic value of NT-proBNP, especially in cardiac originated pleural effusions. Forty-five patients with pleural effusions were included in the study. NT-proBNP levels and biochemical markers involved in the Light's criteria were analyzed in pleural fluid and serums of the patients. Pleural fluid culture, AFB smear, cytology were performed where they were indicated according to the clinical evaluation. In patients, to whom cardiac pathology was considered to be; cardiological evaluation and echocardiography were also done. Thirty-eight pleural effusions were exudative and, 7 were transudative according to the Light's criteria. Final diagnosis were malignant effusion in 13, infection (tuberculosis/pneumonia) in 10, congestive heart failure in 21, and other conditions related with pleural effusion in 1 of the patients. Median (25th to 75th percentiles) NT-proBNP levels of serum and pleural fluid due to congestive heart failure (CHF) were 4747 pg/mL (931-15754) and 4827 pg/mL (1290-12.430) while median NT-proBNP levels of serum and pleural fluid related with non-cardiac reasons were 183 pg/mL (138-444) and 245 pg/mL (187-556) respectively. NT-proBNP levels of serum and pleural fluid were significantly high in CHF (p< 0.001 for both). When four groups were compared serum and pleural fluid NT-proBNP levels were highest in the CHF group which was followed by malignancy, infection and others (p< 0.001 for both). Fourteen of 21 patients who were accepted to have congestive heart failure as the final diagnosis by a cardiological evaluation had an exudative pleural fluid according to the Light's criteria. Serum and pleural fluid NT-proBNP levels were higher in transudates and this reached statistically significance for pleural fluid (p= 0.009). We suggest that measurement of pleural fluid NT-proBNP is a smart approach and pleural fluid NT-proBNP can reflect cardiac origin of effusions better than serum NT-proBNP and Light's criteria.