Serum Cystatin C Does Not Predict Mortality or Treatment Failure in Peritoneal Dialysis: A Prospective Study.

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Background: Small solute clearance, especially that derived from residual renal function (RRF), is an independent risk factor for death in peritoneal dialysis (PD) patients. Assessment of solute clearance is time-consuming and prone to multiple errors. Cystatin C is a small protein which has been used as a glomerular filtration rate (GFR) marker. We investigated whether serum cystatin C concentrations are related to mortality in patients receiving PD. ♦

Methods: New and prevalent PD patients (n = 235) underwent assessment of Kt/Vurea, RRF, weekly creatinine clearance (CCr), normalized protein catabolic rate (nPCR) and a peritoneal equilibration test (PET) at intervals. Blood was collected simultaneously for cystatin C measurement. Patients were followed for a median of 1,429 days (range 12 to 2,964 days) until death or study closure. Cause of death was recorded where given. Cox regression was performed to determine whether cystatin C had prognostic value either independently or with adjustment for other factors (age, sex, dialysis modality, diabetic status, cardiovascular comorbidity, Kt/V, CCr, RRF, nPCR or 4 h dialysate to plasma creatinine ratio (4 h D/Pcr) during the PET). The primary outcomes were all-cause mortality and treatment failure. ♦

Results: There were 93 deaths. Increasing age and 4 h D/Pcr ratio, decreased RRF and presence of diabetes were significantly [p < 0.05] negatively associated with survival and treatment failure. Serum cystatin C was not related to either outcome. ♦

Conclusions: Serum cystatin C concentration does not predict mortality or treatment failure in patients receiving PD.