Relationship between serum cystatin C and creatinine or dialysis adequacy in patients on chronic maintenance hemodialysis

Levels of cystatin C in low- and high-flux hemodialysis in children with end-stage renal disease

BACKGROUND

Cystatin-C (CyC) is a middle molecule that is freely filtered at the glomerulus and almost completely reabsorbed by the proximal tubules. The aim of this study was to evaluate serum CyC and its reduction ratio as a biomarker for assessing the adequacy of the hemodialysis (HD) sessions in children with end-stage renal disease on maintenance HD. We also compared levels of CyC in patients on low-flux HD (LFH) and high-flux HD (HFH).

METHODS

Forty patients were included in the study and divided into two groups, with one group (16 patients) receiving HFH and the other group receiving LFH (24 patients) (high-flux and low-flux polysulfone filters, respectively). Before and after each dialysis session serum CyC and beta-2-microglobulin (B2M) levels were measured using an ELISA technique, and routine laboratory tests were performed for each patient.

RESULTS

Pre-dialytic levels of CyC were significantly lower in the patients receiving HFH than in those receiving LFH (7.33 ± 1.35 vs. 9.73 ± 0.93, respectively; p < 0.0001). In the HFH group, post-dialytic levels of serum CyC were significantly lower than pre-dialytic levels (4.49 ± 0.71 vs. 7.33 ± 1.35, respectively; p < 0.0001). The reduction ratio (RR) of CyC was significantly higher in the HFH group than in the LFH group (38.2 ± 3.91 vs. -6.49 ± 5.05, respectively; p < 0.0001). Serum CyC level significantly correlated with B2M, urea and creatinine levels in both the LFH and HFH groups, whereas its RR significantly correlated with the RRs of urea, creatinine, and B2M in the HFH group.

CONCLUSION

The results of our study emphasize the role of CyC as a good marker for assessing the adequacy of HD sessions in children on HFH and show that the CyC RR may be used as an index of middle-molecule toxin clearance following HFH sessions.

Serum cystatin C as a marker of renal function in critically ill patients with normal serum creatinine

Background:

Serum creatinine as a classic marker of renal function has several limitations in the detection of renal dysfunction.

Objectives:

This study assessed the validity of serum cystatin C as a marker of renal function in critically ill patients with normal serum creatinine.

Patients and Methods:

Eighty adult patients referred to intensive care units with serum creatinine levels < 1.5 mg/dL and without hemodynamic instability were chosen and their serum creatinine and cystatin C levels were measured. A 24-hour urine sample was collected to calculate creatinine clearance (Ccr). Renal dysfunction was defined as Ccr < 80 mL/min/1.73 m².

Results:

There were significant correlations between measured Ccr and 1/serum creatinine (R = 0.51, P < 0.001) and 1/serum cystatin C (R = 0.25, P = 0.028). The difference between false negative rates of serum creatinine (93.33%) and cystatin C (80%) in the detection of renal dysfunction was significant (P = 0.032). Receiver operating characteristic curve analysis illustrated that area under the curve of serum creatinine and cystatin C for detecting renal dysfunction were 0.711 and 0.607, respectively; however, this difference was not significant (P = 0.222).

Conclusions:

Our data demonstrated that serum cystatin C is not superior to serum creatinine in the early detection of renal dysfunction in critically ill patients.