A Comparison of Estimated Glomerular Filtration Rate (eGFR) Based On Serum Creatinine and Cystatin C in Kidney Transplant (KT) Patients.

Abstract

Background: eGFR based on serum creatinine (SCr) is imprecise but routinely used. Such imprecision can potentially affect chronic kidney disease (CKD) stage classification. Cystatin C is an alternative endogenous marker of GFR. Currently, there is scarce data regarding the usefulness of eGFR based on cystatin C in KT patients. Aim: to compare the Chronic Kidney Disease Epidemiology Colaboration (CKD-EPI) SCr and CKD-EPI cystatin C for estimation of GFR and CKD stage classification in KT patients. Methods: GFR was estimated using SCr and cystatin C based CKD-EPI equations in 58 KT patients beyond 6 months post-KT (ages 19-73, male 67%, cadaveric donor 74%). Patients were classified in CKD stages according to National Kidney Foundation guidelines based on the eGFR obtained from these equations. Data are expressed as:median, range. Results: SCr (mg/dl) and cystatin C were 1.32, 0.55-5.2 and 1.72, 0.79-4.3 respectively. Overall eGFR (ml/min/1.73 m2) was significantly different between SCr and cystatin C based equations (55, 13-122 and 41.5, 12-128 respectively) (p<0.0012). No significant differences were found in CKD stage classification except in stage IV, 6.9% vs 25.9% patients according to SCr and cystatin C CKD-EPI( p<0.005). Correlation between both equations was good (r2=0.88) (fig. 1). The Bland-Altman graph shows most values are within 1.96 SD from the mean (fig.2).Figure: No Caption available.Conclusion: eGFR from SCr based CKD-EPI is different from cystatin C based CKD-EPI in the population studied. Both methods require further efforts to establish their utility as GFR estimates in KT patients.