N-terminal pro-brain natriuretic peptide and cardiorenal outcome in patients with anaemia in chronic kidney disease

Aims Blood levels of N-terminal pro-brain natriuretic peptide (NT-proBNP) may be modified by low renal clearance and anaemia. The aim of this study was to investigate the impact of the blood NT-proBNP level on cardiovascular and renal outcomes in patients with these two manifestations. Methods This post hoc analysis stemmed from the oBservational clinical Research In chronic kidney disease patients with renal anemia: renal proGnosis in patients with Hyporesponsive anemia To Erythropoiesis-stimulating agents, darbepoetiN alfa (BRIGHTEN) trial, a large prospective study involving patients with non-dialysis kidney disease experiencing anaemia. The Pearson correlation coefficient was employed to examine the association of baseline NT-proBNP level with renal function or anaemia. Longitudinal assessment of the association of baseline blood NT-proBNP levels with cardiovascular outcomes (cardiac death, acute coronary syndrome, hospitalization due to heart failure or fatal arrhythmia) and renal outcomes [the initiation of maintenance dialysis, kidney transplantation, a 50% decrease in the estimated glomerular filtration rate (eGFR) or an eGFR of <= 6 mL/min/1.73 m(2)] was conducted by using restricted cubic spline analysis and Cox proportional hazard model analysis. Results In total, this study included 1484 patients [mean age, 70.2 +/- 11.8 years; women, 40.6%; eGFR, 20.3 +/- 9.6 mL/min/1.73 m(2); haemoglobin (Hb) level, 9.8 +/- 0.9 g/dL]. Baseline NT-proBNP levels were a median of 496.0 pg/mL [inter-quartile range: 235.0-1090.0 pg/mL]. A weak association existed between NT-proBNP levels, on a logarithmic scale, and eGFR (r = -0.131, P < 0.001) or Hb levels (r = -0.182, P < 0.001) at baseline. During 2.29 +/- 0.89 years, 92 cardiovascular and 573 renal events were recorded. After adjusting for potential confounders such as eGFR and blood Hb level, a nonlinear relationship existed between blood NT-proBNP levels and cardiorenal outcomes. Patients with a baseline NT-proBNP level >= 1000 and 500-1000 pg/mL exhibited a greater risk for cardiovascular outcomes than did patients with an NT-proBNP level <250 pg/mL {hazard ratio [HR] = 8.10 [95% confidence interval (CI), 2.80-23.40] and 3.35 [95% CI, 1.10-10.18], respectively}. These patients also exhibited a moderate risk for renal outcomes [HR = 1.77 (95% CI, 1.36-2.31) and 1.54 (95% CI, 1.19-2.00), respectively]. Conclusions NT-proBNP provides prognostic insights into cardiovascular and renal outcomes among patients with advanced chronic kidney disease experiencing anaemia.