PURPOSE: Pleural fluid N-terminal-pro-B-type natriuretic peptide (NT-proBNP) concentrations >1500 pg/ml as well as serum B-type natriuretic peptide (BNP) levels >500 pg/ml are almost diagnostic of congestive heart failure (CHF). Conversely, serum BNP levels below 100 pg/ml make the diagnosis of CHF rather unlikely. The aim of this study was to evaluate the role of pleural fluid BNP in the diagnosis of cardiac pleural effusions.
METHODS: The study prospectively evaluated serum and pleural fluid BNP in fourteen patients with effusions attributed to CHF (group A, n = 7) and other causes (group B, n = 7). The diagnosis of heart failure was based on clinical criteria, according to the ACC/AHA guidelines, and blinded to the BNP results. Measurements of BNP levels were made by an electrochemiluminiscence immunoassay. Serum (BNPser) and pleural fluid (BNPpf) BNP levels as well as pleural fluid-to-serum BNP ratio (BNP ratio) and serum-fluid BNP gradient (BNP gradient) were compared between patients with and without CHF.
RESULTS: According to Light's criteria, group A included four (57%) transudates and three (43%) exudates while group B comprised of five (71%) exudates and two (29%) transudates attributable to nephrosis. BNPser, BNPpf, BNP ratio and BNP gradient were significantly different (p<0.05) between group A and group B but not between transudates (n=6) and exudates (n=8). Only BNP ratio could separate (p<0.0001) group A from group's B transudates (n=2).
CONCLUSION: BNP could not separate transudates from exudates. BNPser, BNPpf, BNP ratio and BNP gradient may have a role in the diagnosis of pleural effusions due to CHF. Higher BNP ratios in non-cardiac pleural effusions could possibly be due to increased pleura's permeability, local production, or decreased removal from pleural cavity. Nevertheless, additional studies with more patients are needed to confirm these results.
CLINICAL IMPLICATIONS: Pleural fluid BNP levels could be used instead of pleural fluid NT-proBNP in the diagnosis of cardiac pleural effusions while BNP ratio could be helpful in separating cardiac effusions when BNPser levels range in the “grey area” of 100–500 pg/ml.
DISCLOSURE: Vasileios Skouras, No Financial Disclosure Information; No Product/Research Disclosure Information