Is N-terminal probrain-type natriuretic peptide a clinically useful biomarker of volume overload in peritoneal dialysis patients?

BACKGROUND: Brain natriuretic peptide (BNP) has been reported to be a powerful predictor of peritoneal dialysis patient survival. However, it is unclear as to whether this is related to cardiac dysfunction or chronic volume overload. METHODS: To investigate the relationship between BNP, cardiac function and fluid volume overload, we reviewed multifrequency bioimpedance, transthoracic echocardiography and serum N-terminal probrain-type natriuretic peptide (NTproBNP) in 115 stable peritoneal dialysis outpatients attending for assessment of peritoneal dialysis and transport status. RESULTS: In this cross-sectional study, the median NTproBNP was 251 (118-605) pmol/L. On simple univariate analysis, NTproBNP was associated with markers of residual renal function, volume overload, hypertension and hypertensive cardiac disease and inflammation [reduced serum albumin and raised C-reactive protein]. However, on multivariate logistical regression analysis, the strongest association for log NTproBNP was with the estimated right ventricular end-systolic pressure (β = 0.02, F = 11.5, P = 0.001), followed by log 24-h urine volume (β = -0.19, F = 10.7, P = 0.002), extracellular/total body water ratio (β = 13.5, F = 6.1, P = 0.017) and the number of different antihypertensive medications prescribed (β = 0.15, F = 8.7, P = 0.005). CONCLUSION: In this cross-sectional study, although NTproBNP was associated with residual renal function, cardiac hypertrophy, volume overload and inflammation on simple univariate analysis, on further examination NTproBNP was predominantly affected by factors associated with volume overload, and these results require confirmation in a prospective study.