Purpose of review: Natriuretic peptides are secreted by the myocardium in response to mechanical stretch and have been proposed as a possible test for assisting the diagnosis of heart failure. This article reviews the rationale for measuring N terminal probrain natriuretic peptide in pleural fluid to identify heart failure as the cause of a pleural effusion.
Recent findings: Rapid and accurate testing of natriuretic peptides as biomarkers for heart failure is now a clinical reality. In patients presenting with dyspnea, heart failure is usually absent at blood brain natriuretic peptide levels less than 100 pg/mL, possible from 100 to 500 pg/mL, and probable at levels greater than 500 pg/mL. In evaluating natriuretic peptide assays, one needs to consider carefully laboratory and biologic variation, including gender, sex, obesity, renal function, and the assay used. Potential future applications of natriuretic peptide testing include the differential diagnosis of pleural effusion. A recent study has shown good diagnostic characteristics in cardiac pleural effusions, with likelihood ratios of 13 and a diagnostic accuracy of more than 90% for pleural fluid N terminal probrain natriuretic peptide levels > or =1500 pg/mL. Specifically, N terminal probrain natriuretic peptide pleural levels correctly categorized most cardiac effusions misclassified as exudates by standard criteria, and discriminated between cardiac and hepatic transudates.
Summary: Pleural fluid N terminal probrain natriuretic peptide may help accurately differentiate cardiac from noncardiac conditions in patients presenting with pleural effusion.