Clinical effect of obesity on N‐terminal pro‐B‐type natriuretic peptide cut‐off concentrations for the diagnosis of acute heart failure

AIMS: Obese patients have lower natriuretic peptide concentrations. We hypothesized that adjusting the concentration of N‐terminal pro‐B‐type natriuretic peptide (NT‐proBNP) for obesity could further increase its clinical utility in the early diagnosis of acute heart failure (AHF). METHODS AND RESULTS: This hypothesis was tested in a prospective diagnostic study enrolling unselected patients presenting to the emergency department with acute dyspnoea. Two independent cardiologists/internists centrally adjudicated the final diagnosis using all individual patient information including cardiac imaging. NT‐proBNP plasma concentrations were applied: first, using currently recommended cut‐offs; second, using cut‐offs lowered by 33% with body mass index (BMI) of 30–34.9 kg/m(2) and by 50% with BMI ≥ 35 kg/m(2). Among 2038 patients, 509 (25%) were obese, of which 271 (53%) had AHF. The diagnostic accuracy of NT‐proBNP as quantified by the area under the receiver‐operating characteristic curve was lower in obese versus non‐obese patients (0.890 vs. 0.938). For rapid AHF rule‐out in obese patients, the currently recommended cut‐off of 300 pg/ml achieved a sensitivity of 96.7% (95% confidence interval [CI] 93.8–98.2%), ruling out 29% of patients and missing 9 AHF patients. For rapid AHF rule‐in, the age‐dependent cut‐off concentrations (age <50 years: 450 pg/ml; age 50–75 years: 900 pg/ml; age >75 years: 1800 pg/ml) achieved a specificity of 84.9% (95% CI 79.8–88.9%). Proportionally lowering the currently recommended cut‐offs by BMI increased sensitivity to 98.2% (95% CI 95.8–99.2%), missing 5 AHF patients; reduced the proportion of AHF patients remaining in the ‘gray zone’ (48% vs. 26%; p = 0.002), achieving a specificity of 76.5% (95% CI 70.7–81.4%). CONCLUSIONS: Adjusting NT‐proBNP concentrations for obesity seems to further increase its clinical utility in the early diagnosis of AHF.