B-Type Natriuretic Peptide (BNP) and N-Terminal Pro-BNP in Obese Patients without Heart Failure: Relationship to Body Mass Index and Gastric Bypass Surgery

better characterize variables that that may confound the clinical interpretation of plasma natriuretic peptide measurements, which are increasingly recognized to have diagnostic and predictive importance. Methods: Blood samples (EDTA plasma) from patients (n 206) attending clinics for the medical treatment and follow-up of obesity were analyzed for B-type natri-uretic peptide (BNP; Bayer assay) and the N-terminal segment of its prohormone (NT-proBNP; Roche assay). Natriuretic peptide concentration ranges were evaluated in those without diagnosis of congestive heart failure (CHF) or chronic kidney disease (CKD). Results: BNP and NT-proBNP were directly correlated (r 0.87; P 0.01), with NT-proBNP concentrations higher relative to BNP. Of obese patients without CHF or CKD, 21.6 % (40 of 185) had NT-proBNP concentra-tions greater than the published assay upper reference limit. Concentrations of both natriuretic peptides were higher in patients currently exposed to beta blockers, patients with the diagnosis of hypertension or type 2 diabetes, and patients with a history of gastric bypass surgery. An inverse relationship between body mass index (BMI) and both BNP and NT-proBNP was evi-dent. According to the National Institutes of Health, National Heart, Lung, and Blood Institute classification, more than 95 % of the participants sampled in this study were either obesity class 2 (35> BMI < 39.9 kg/m2) or class 3 (BMI>40 kg/m2) Conclusions: A substantial proportion of obese patients without CHF or CKD have concentrations greater than the upper reference limit for NT-proBNP but not for simultaneously measured BNP. A history of gastric bypass surgery appeared to be a significant predictor of increased natriuretic peptide concentrations when as-sessed in a population of patients with class 2 or 3 obesity. © 2006 American Association for Clinical Chemistry Physiologic and pathologic states leading to volume ex-pansion and/or increased tension on cardiac myocytes lead to up-regulation of signals for the production and secretion of cardiac natriuretic prohormones, includin