Impact of Increased Body Mass Index on Accuracy of B-Type Natriuretic Peptide (BNP) and N-Terminal proBNP for Diagnosis of Decompensated Heart Failure and Prediction of All-Cause Mortality

Abstract

Background: BNP and N-terminal proBNP (NT-proBNP) concentrations may be depressed in patients with increased body mass index (BMI). Whether increased BMI affects accuracy of these biomarkers for diagnosing decompensated heart failure (HF) and predicting outcomes is unknown. Methods: We measured BNP and NT-proBNP in 685 patients with possible decompensated HF in a free-living community population subdivided by BMI as obese, overweight, and normal weight. HF diagnosis was adjudicated by a cardiologist blinded to BNP and NT-proBNP results. We tabulated all-cause mortality over a median follow-up of 401 days and assessed marker accuracy for HF diagnosis and mortality by ROC analysis. Results: Of the 685 patients, 40.9% were obese (n = 280), 28.2% were overweight (n = 193), and 30.9% had normal BMI (n = 212). Obese patients had lower BNP and NT-proBNP compared with overweight or normal-weight individuals (P < 0.001) and decreased mortality compared with normal-weight individuals (P < 0.001). Both biomarkers added significantly to a multivariate logistic regression model for diagnosis of decompensated HF across BMI categories. NT-proBNP outperformed BNP for predicting all-cause mortality in normal-weight individuals (χ2 for BNP = 6.4, P = 0.09; χ2 for NT-proBNP = 16.5, P < 0.001). Multivariate regression showed that both biomarkers remained significant predictors of decompensated HF diagnosis in each BMI subgroup. Conclusions: In this study population, obese patients had significantly lower BNP and NT-proBNP that reflected lower mortality. BNP and NT-proBNP can be used in all BMI groups for decompensated HF diagnosis, although BMI-specific cutpoints may be necessary to optimize sensitivity.

Current Diagnostic and Treatment Strategies for Specific Dilated Cardiomyopathies: A Scientific Statement From the American Heart Association

“…This makes levels of natriuretic peptide less helpful in the diagnosis of HF in obese patients, because patients can have normal or minimally elevated levels of BNP, even in the setting of acute decompensated HF and elevated filling pressures. 359,360 Because signs and symptoms of dyspnea and edema are not specific for HF in obese patients, and jugular venous pressure can be difficult to estimate accurately because of body habitus, hemodynamic confirmation may be needed more often in obese than in lean patients to confirm the clinical diagnosis of HF.…”

Obesity and natriuretic peptides, BNP and NT-proBNP: Mechanisms and diagnostic implications for heart failure

“…Based on the established clinical threshold of 100 pg/mL, BNP testing yielded false negative results in 20% of obese HF patients [6,116]. Hence, a cut point of BNP ≤ 54 pg/mL is recommended for ruling out CHF in severely obese patients (BMI ≥ 35) (Table 1) [6].…”

The paradox of low BNP levels in obesity

“…Some studies were based on large population [4,5,62,63,106], including both healthy adult subjects and patients with various disorders (only patients with HF were excluded), while other studies included only patients with HF [8][9][10][11]105] (Table 2). However, conflicting results were also reported; Kanda et al [113] found no significant correlation between BNP to BMI values in a general Japanese population, including 686 apparently healthy subjects.…”

“…This phenomenon, termed ''reverse epidemiology'' and involving about 20 million Americans, may be due to the overwhelming effect of the malnutrition-inflammation complex syndrome (MICS) [131]. The presence of MICS in some patients contributes to explain the inverse correlation between BMI and BNP values in HF [6,[8][9][10][11]105]. BNP production/secretion is greatly increased in elderly HF patients with severe disease, hemodynamic impairment, and activation of counteracting neurohormone (including adrenergic, renin-angiotensin-aldosterone, and endothelin) and cytokine systems compared to asymptomatic subjects [13,[30][31][32][33][34][35].…”