Relationship between Natriuretic Peptide Concentrations in Plasma and Posture during Blood Sampling

Measurements of the plasma concentrations of one or more of the natriuretic peptides can be a valuable tool in the diagnosis, prognosis, and follow-up of patients with cardiac dysfunction (1)(2). Measurement techniques have also improved, allowing for less time-consuming direct assays than previous methods, which often required the prior extraction of peptides from plasma. However, improvement is still needed (3). In most research settings, blood sampling is performed under carefully controlled conditions, involving the introduction of a catheter and ample bed rest before the collection of blood. Such procedures are necessary for the reliable interpretation of many neurohormone measurements. Catecholamines, for example, can fluctuate widely depending on the blood-sampling procedure and posture. Because strictly adhering to rigorous blood-sampling protocols is often impossible in everyday clinical situations, we investigated the variation in measured natriuretic peptide concentrations because of differences in blood-sampling conditions. We have measured atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), N-terminal-pro-ANP (Nt-ANP), as well as the catecholamines noradrenaline (NOR), adrenaline, renin (REN), and aldosterone (ALDO). We studied subjects in the relevant age range (>40 years) with diseases of interest in four different blood-sampling conditions, while continuing appropriate medications for these conditions. Twenty-three subjects (55 ± 10 years; range 42–74 years) participated in the study after giving their informed consent. Six subjects were apparently healthy controls (46 ± 5 years; two females), nine were hypertensive patients (53 ± 7 years; two females), and eight (64 ± 9 years; three females) were patients with diseases known to lead to increased concentrations of natriuretic peptides: congestive heart failure (four subjects) and chronic renal failure …