Kidney function crucially affects B-type natriuretic peptide (BNP), N-terminal proBNP and their relationship.

BACKGROUND: B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) are useful biomarkers in the management of heart failure. Both peptides are secreted into the circulation after cleavage of their precursor proBNP and excreted from the kidney in the active form or as metabolites. We investigated effects of kidney function on the levels and association of these peptides.

MATERIALS AND METHODS: Plasma concentrations of BNP and serum concentrations of NT-proBNP were measured in 229 outpatients of our cardiology department (male/female = 138/91, mean age= 68 years) and 53 hospital outpatients on chronic haemodialysis (30/23, 68 years). Kidney function in nondialysed patients was assessed by estimated glomerular filtration rate (eGFR; mL/min/1.73 m(2)) and categorised across five stages. Effects of kidney function on BNP, NT-proBNP and their relationship were investigated.

RESULTS: Deterioration in kidney function increased BNP and NT-proBNP levels, as well as the NT-proBNP/BNP ratio, and these values were highest in patients on haemodialysis. The eGFR inversely correlated with BNP (r = -0.472), NT-proBNP (r = -0.579), and the NT-proBNP/BNP ratio (r = -0.454, all P < 0.0001). A significant correlation was observed between BNP and NT-proBNP at all stages of kidney function including patients on haemodialysis, but the correlation was significantly affected by kidney function.

CONCLUSIONS: Although circulating levels of both BNP and NT-proBNP increased with deteriorating kidney function, the impact of kidney function on NT-proBNP was much more pronounced than that on BNP. Kidney function should be taken into account when interpreting data on BNP, NT-proBNP and their relationship.