Cystatin C reduction ratio depends on normalized blood liters processed and fluid removal during hemodialysis

A negative correlation between the weekly standard Kt/V (urea) and serum cystatin C level (CysC) in functionally anephric dialysis patients has been previously demonstrated. Our objective was to measure the per dialysis CysC reduction ratio (CCRR) and to compare it with other indices of dialytic functions.

In a pilot cross-sectional study of 15 functionally anephric patients on conventional high-flux high-efficiency hemodialysis three times per week, CysC levels were drawn pre-, mid-, and postdialysis over 1 week. CCRR was compared with single-pool Kt/V (Sp Kt/V) using urea kinetic modeling, urea reduction ratio (URR), creatinine reduction ratio (CRR), normalized liters processed (LP/kg), and ultrafiltration volume (UF). Normally distributed data (Shapiro-Wilks test) were described as mean±SD, otherwise as median and interquartile range.

The mean pre- and post-CysC levels were 6.0±1.0 and 4.7±1.1 mg/L. The Sp Kt/V and Std Kt/V were 1.5±0.2 and 2.6. The URR, CRR, and CCRR were 70.2%±9.0%, 64.5%±8.2%, and 26.1%±11.8%, respectively. There was no correlation between the CCRR, and the Sp Kt/V, URR, and CRR, whereas CCRR correlated with LP/kg and UF. Multiple regression analysis with these two parameters provided a model that explained 81% of the variance.

Our data suggest that normalized liters processed and ultrafiltration volume explain most of the variance of CCRR. Therefore, CCRR may be an excellent method to monitor dialysis efficiency of low molecular weight proteins.