Are natriuretic peptides a reliable marker for mortality in ESRD patients?

Among the markers of cardiovascular diseases (CVDs) studied in the last 15–20 years, both B-type natriuretic peptide (BNP) and its N-terminal fragment (NT-proBNP) represent a very interesting group of markers. Several studies have demonstrated their role in the development of cardiac failure and other CVD, and BNP has been introduced in the interventional guideline algorithms proposed by the main scientific societies [1,2]. These guidelines suggest analysing BNP and NT-proBNP in untreated but symptomatic patients, and levels of BNP >400 pg/mL and NT-proBNP >2000 pg/mL are considered suggestive for chronic heart failure. It is well known that CVDs are the most frequent cause of morbidity and mortality in patients with chronic kidney disease (CKD) [3], and individuals with CKD have up to 20-fold greater risks of cardiac death, compared to ageand sex-matched controls without CKD. It has also been demonstrated that plasma levels of BNP are increased both in non-dialysisand dialysis-dependent CKD patients. BNP is a reliable test to diagnose significant structural or functional CVDs even in children [4]. Natriuretic peptides (NPs) offer the potential for early detection and risk stratification of CVD in patients admitted to the emergency department [5]. These markers could also be useful for CKD patients asymptomatic for CVD [6]. In this issue of the Journal, Paniagua et al. [7] publish an interesting paper, highlighting what several previous papers demonstrated mainly in the general population, i.e. both BNP and proBNP plasma values in CKD stage 5D patients are directly correlated with extracellular fluid expansion and left ventricular myocardial mass, and are inversely closely correlated with residual renal function [8–11]. High NP values are also associated with inflammation, while there is no clear correlation with obesity and diabetes [12,13]. Besides, NT-proBNP levels are both markers of myocardial damage and fluid overload [9,10]. In the family of NPs, NT-proBNP seems to be the best predictor of clinical outcome and marker of extracellular fluid overload. In fact, the synthesis of NT-proBNP in the left ventricle represents a response to stimuli requiring greater ventricular work. This peptide is larger and has a longer half-life than BNP (the active form), making its measurement easier and also less dependent on acute changes, while this is an important factor affecting the concentration of other NPs [14]. During the last years, the value of the NT-proBNP plasma concentration has been a ‘hot topic’ not only as an independent predictor of general and cardiovascular mortality but also as a marker of fluid control in dialysis patients. The role of NT-proBNP as a predictive marker of clinical outcome in patients on dialysis has been proven, but there are no data about its interaction with fluid volume control and dialysis modality. The aim of the paper from Paniagua et al. [6] was just to demonstrate the interaction between NT-proBNP, fluid volume control and different dialysis modalities.