Does Cystatin C have a role as metabolic surrogate in peritoneal dialysis beyond its association with residual renal function?

INTRODUCTION: It has been suggested that cystatin C levels are modified by obesity and inflammation. Furthermore, cystatin C has been associated with cardiovascular events and mortality outcomes. AIM: To study the association of cystatin C with the metabolic profile and cardiovascular disease of peritoneal dialysis patients. METHODS: Data collected included clinical, laboratorial, and multifrequency bioimpedance assessment of 52 stable peritoneal dialysis patients. Minimal residual renal function was defined as > 2mL/min/1.73m2. RESULTS: Serum cystatin C was not significantly associated with peritoneal or urinary cystatin C excretion. Negative correlation of cystatin C with normalized protein catabolic rate (rho -0.33, p = 0.02) and a trend towards positive correlation with relative body fat (rho 0.27, p = 0.05) were not independent from residual renal function. Cystatin C was not significantly associated with cardiovascular disease (p = 0.28), nor with glycated hemoglobin (p = 0.19) or c-reactive protein (p = 0.56). In the multivariate model, both age and diabetes were the strongest predictors of cardiovascular disease (odds ratio 1.09, p = 0.029 and odds ratio 29.95, p = 0.016, respectively), while relative body fat was negatively associated with cardiovascular disease (p = 0.038); neither cystatin C (p = 0.096) nor minimal residual renal function (p = 0.756) reached a significant association with cardiovascular disease. CONCLUSIONS: In this group of peritoneal dialysis patients, cystatin C did not correlate with the metabolic or inflammatory status, nor cardiovascular disease, after adjustment for residual renal function.