B-type natriuretic peptide (BNP) and N-terminal pro-BNP (NT-proBNP) levels can indicate a variety of heart problems, as well as general critical illness. BNP and NT-proBNP assays are useful for evaluating patients with acute dyspnea, as a low level of natriuretic peptide can help rule out congestive heart failure (CHF) and reduce reliance on echocardiography. Conversely, these assays can be particularly useful in recognizing CHF in a patient with acute dyspnea and a history of chronic obstructive pulmonary disease. However, clinical judgment must always be part of the evaluation of BNP or NT-proBNP assay results.