NT-brain natriuretic peptide levels in pleural fluid distinguish between pleural transudates and exudates.

Background: Pleural effusion is not pathognomic and distinguishing between transudates and exudates often presents a diagnostic dilemma. The purpose of our study was to examine whether the inclusion of pleural fluid brain natriuretic peptide (BNP) measurement into the analysis improves the diagnostic accuracy of pleural effusion.

Methods: The pleural effusion of 14 patients with CHF (group A) and 14 subjects with different pleural pathology (group B) were analyzed. Samples of pleural fluid and serum were obtained from all patients on admission and biochemical analysis, bacterial and fungal culture, acid-fast bacilli smear and culture and cytology were performed on the pleural fluid. In vitro quantitative determination of N-terminal pro-Brain natriuretic peptide (NT-proBNP) in serum and pleural fluid were performed by electrochemiluminescence immunoassay proBNP method on an Elecsys 2010 (Roche) analyzer.

Results: The median NT-proBNP levels in groups A and B were 6295 pg/ml and 276 pg/ml, respectively: (P=0.0001). There was no overlap between the two groups. While the Light's criteria had a sensitivity of 93% and specificity of 43% for transudates, the pleural fluid NT-proBNP level accurately differentiated between the two groups.

Conclusions: The pleural NT-proBNP levels were elevated in all patients who had transudate. Therefore if the NT-proBNP levels of pleural effusion are within the normal range, transudate resulting from congestive heart failure can be ruled out. Our results suggest that the inclusion of pleural fluid NT-proBNP measurement in the routine diagnostic panel would enhance discrimination among the different causes of pleural effusions.