OBJECTIVE: Diabetes has been implicated in reduced myocardial compliance and changes in the intercellular matrix of the myocardium. We determined the effect of diabetes on B-type natriuretic peptide (BNP) concentrations in patients presenting to the emergency department with dyspnea. RESEARCH DESIGN AND METHODS: The Breathing Not Properly Multinational Study was a prospective evaluation of 1,586 patients. A subset of 922 patients was obtained and subdivided into the following groups: group 1 (n = 324), neither diabetes nor heart failure; group 2 (n = 107), diabetes and no heart failure; group 3 (n = 247), no diabetes and heart failure; group 4 (n = 183), both diabetes and heart failure; group 5 (n = 41), heart failure history with no diabetes; and group 6 (n = 20), heart failure history with diabetes. Patients from groups 1, 3, and 5 were matched to groups 2, 4, and 6, respectively, to have the same mean age, sex distribution, BMI, renal function, and New York Heart Association (NYHA) classification (for heart failure). RESULTS: There was no significant difference in median BNP levels between diabetes and no diabetes among no heart failure patients (32.4 vs.32.9 pg/ml), heart failure patients (587 vs. 494 pg/ml), and those with a heart failure history (180 vs. 120 pg/ml). Receiver-operating characteristic curve analysis of the area under the curve for BNP was not different in diabetic versus nondiabetic patients (0.888 vs. 0.878, respectively). However, in a multivariate model, diabetes was an independent predictor of a final diagnosis of heart failure (odds ratio 1.51, 95% CI 1.03-2.02; P < 0.05). CONCLUSIONS: History of diabetes does not impact BNP levels measured in patients with acute dyspnea in the emergency department. Despite the impact of diabetes on the cardiovascular system, diabetes does not appear to confound BNP levels in the emergency department diagnosis of heart failure. Copyright 2004 American Diabetes Association