Assessment of Kidney Graft Function Evolution Measured by Creatinine and Cystatin C

The 2013 Kidney Disease Outcomes Quality Initiative Clinical Practice Guideline suggests measuring cystatin C (sCys) in adults with glomerular filtration rate (GFR) based on creatinine (sCr) between 45 and 59 mL/min/1.73 m² if confirmation of chronic kidney disease (CKD) is required. There is not enough evidence to recommend the use of sCys or sCr to estimate GFR in kidney transplant recipients.

Our aims were to describe the evolution of sCr, sCys, and GFR in a group of kidney transplant patients and to determine their association with some markers of morbidity at 1 year.

A total of 54 patients were included. Analytical and clinical data were recorded. Renal function was analyzed using the CKD Epidemiology Collaboration (EPI) sCr equation and CKD-EPI sCys equation.

sCys-estimated GFR was higher than estimated from sCr by CKD-EPI. The values of sCys have more variability than those of sCr. The agreement between the stages of CKD by sCr or sCys-estimated GFR measured by Cohen's kappa coefficient was only fair. One-year CKD-associated variables correlated differently with sCr and sCys-estimated GFR. Hemoglobin, uric acid, calcium, and phosphorus related to sCr-estimated GFR, whereas serum albumin was associated with sCys-estimated GFR.

sCys values have a higher variability than sCr in kidney transplant recipients. sCys- or sCr-based GFRs have a nonsimilar behavior in these patients with weak agreement to stratify CKD stages and a different relationship to CKD-related comorbid conditions.