How Obesity Affects the Cut-Points for B-Type Natriuretic Peptide in the Diagnosis of Acute Heart Failure

Lori B. Daniels, MD; Paul Clopton, MS; Vikas Bhalla, MD; Padma Krishnaswamy, MD; Richard M. Nowak, MD, MBA; James McCord, MD; Judd E. Hollander, MD; Philippe Duc, MD; Torbjørn Omland, MD, PhD; Alan B. Storrow, MD; William T. Abraham, MD; Alan H.B. Wu, PhD; Philippe G. Steg, MD; Arne Westheim, MD, PhD, MPH; Cathrine Wold Knudsen, MD; Alberto Perez, MD; Radmila Kazanegra, MD; Howard C. Herrmann, MD; Peter A. McCullough, MD, MPH; Alan S. Maisel, MD

Disclosures

Am Heart J. 2006;151(5):999-1005. 

In This Article

Abstract and Introduction

Abstract

Background: 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 BNP ≥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.
Methods: 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.
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.
Conclusions: Body mass index influences the selection of cut-points for BNP in diagnosing acute HF. A lower cut-point (BNP ≥54 pg/mL) should be used in severely obese patients to preserve sensitivity. A higher cut-point in lean patients (BNP ≥170 pg/mL) could be used to increase specificity.

Introduction

Heart failure (HF) is a serious personal and public health problem that affects >5 million Americans, resulting in massive disability and health care costs.[1] Several studies have shown that obesity is a major modifiable risk factor for congestive HF (CHF),[2,3,4,5,6] impacting both systolic and diastolic ventricular function[7,8,9,10,11] as well as coronary artery disease.[12,13] With the growing pandemic of obesity in the United States and elsewhere,[14,15] the scope of the problem of HF is likely to continue to increase.

B-type natriuretic peptide (BNP) is useful in establishing or excluding the diagnosis of CHF in patients who present to the emergency department (ED) with acute dyspnea.[16] However, recent studies have shown that obese and overweight individuals have considerably lower circulating natriuretic peptide levels compared with individuals with a normal body mass index (BMI).[17,18,19] The lower levels of BNP relative to lean patients seem to persist even when obese patients are in HF, despite a similar severity of HF.[20,21]

Despite that obese patients have lower BNP levels, little is known about how to interpret BNP for diagnosing CHF in this population. For the general population, studies have suggested a cut-point of BNP ≥100 pg/mL for the diagnosis of CHF.[16] We sought to determine whether the optimal cut-point for BNP in diagnosing acute CHF changes with BMI and, if so, to develop an algorithm to improve diagnosis.

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