How obesity affects the cut-points for B-type natriuretic peptide in the diagnosis of acute heart failure. Results from the Breathing Not Properly Multinational Study

B-type natriuretic peptide (BNP) is valuable in diagnosing heart failure (HF), but its utility in obese patients is unknown. Studies have suggested a cut-point of BNPor = 100 pg/mL for the diagnosis of HF; however, there is an inverse relation between BNP levels and body mass index. We evaluated differential cut-points for BNP in diagnosing acute HF across body mass index levels to determine whether alternative cut-points can improve diagnosis.The Breathing Not Properly Multinational Study was a 7-center, prospective study of 1586 patients who presented to the Emergency Department with acute dyspnea. B-type natriuretic peptide was measured on arrival. Height and weight data were available for 1368 participants. The clinical diagnosis of HF was adjudicated by 2 independent cardiologists who were blinded to BNP results.Heart failure was the final diagnosis in 46.1%. Mean BNP levels (pg/mL) in lean, overweight/obese, and severely/morbidly obese patients were 643, 462, and 247 for patients with acute HF, and 52, 35, and 25 in those without HF, respectively (P.05 for all comparisons except 35 vs 25). B-type natriuretic peptide cut-points to maintain 90% sensitivity for a HF diagnosis were 170 pg/mL for lean subjects, 110 pg/mL for overweight/obese subjects, and 54 pg/mL in severely/morbidly obese patients.Body mass index influences the selection of cut-points for BNP in diagnosing acute HF. A lower cut-point (BNPor = 54 pg/mL) should be used in severely obese patients to preserve sensitivity. A higher cut-point in lean patients (BNPor = 170 pg/mL) could be used to increase specificity.