D espite the clinical usefulness of the well-established Light criteria, differentiating transudative from exudative pleural effusions can still prove diffi cult in the setting of cardiovascular disease, particularly following the administration of diuretics. In recent years the brain natriuretic peptides have emerged as potential diagnostic markers capable of identifying effusions resulting from congestive heart failure (CHF). Brain natriuretic peptide-32 (BNP) and N-terminal pro-brain natriuretic peptide (NT-proBNP) are derived from the precursor peptide proBNP and are secreted into the circulation in equimolar Background: Current evidence indicates that measurement of pleural fl uid N-terminal pro-brain natriuretic peptide (NT-proBNP) levels can aid in distinguishing pleural effusions of cardiac origin from those of noncardiac origin. To date, only one study, to our knowledge, has described simultaneous measurement of pleural fl uid brain natriuretic-32 peptide (BNP) and NT-proBNP. The purpose of the present study was to determine pleural fl uid BNP and NT-proBNP levels and analyze the relationship between these two measurements. We hypothesized that there would be a positive correlation between pleural fl uid NT-proBNP and BNP, whereas NT-proBNP levels would be higher than BNP levels. Methods: Levels of pleural fl uid NT-proBNP and BNP were measured by enzyme immunoassay in a total of 80 patients: 20 with congestive heart failure, 20 status post-coronary artery bypass graft, 20 with carcinoma, and 20 with pneumonia. Results: Comparison of NT-proBNP and BNP concentrations using the Spearman method of statistical analysis revealed a correlation coeffi cient of 0.572, P , .001. Evaluation of the diagnostic accuracy of BNP and NT-proBNP in patients with pleural effusions of cardiac origin demonstrated an area under the receiver operating characteristic curve of 0.700 (95% CI, 0.569-0.831) and 0.835 (95% CI, 0.721-0.949), respectively. Conclusions: Although levels of pleural fl uid BNP have a statistically signifi cant correlation with those of NT-proBNP, this relationship only explains 32% of the variance in NT-proBNP levels. Furthermore, when compared with BNP, NT-proBNP is a more accurate diagnostic aid in the evaluation of pleural effusions of cardiac origin. CHEST 2010; 137(6):1369-1374 Abbreviations: AUC 5 area under the curve; BNP 5 brain natriuretic-32 peptide; CABG 5 coronary artery bypass graft; CHF 5 congestive heart failure; EIA 5 enzyme immunoassay; NT-proBNP 5 N-terminal pro-brain natriuretic peptide; ROC 5 receiver operating characteristic

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Abbreviations: AUC 5 area under the curve; BNP 5 brain natriuretic-32 peptide; CABG 5 coronary artery bypass graft; CHF 5 congestive heart failure; EIA 5 enzyme immunoassay; NT-proBNP 5 N-terminal pro-brain natriuretic peptide; ROC 5 receiver operating characteristic