Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation to estimate GFR (eGFR)

Chronic kidney disease is monitored by glomerular filtration rate (GFR)

• measured GFR is not widely used whereas estimates of GFR based on levels of serum creatinine are commonly used but can be inaccurate
• cross sectional studies suggest that inclusion of cystatin C with creatinine in combined GFR estimating equations can improve the accuracy of assessing GFR

The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) developed equations to calculate eGFR based on serum creatinine; and another equation based on serum creatinine plus serum cystatin C

• in patients with near-normal kidney function, the Modification of Diet in Renal Disease (MDRD) equations underestimate GFR
  • the CKD-EPI2009Scr equation partly overcomes the major limitation of the MDRD equation
• the CKD-EPI working group developed two CKD-EPI equations (2):
  • one using cystatin C concentration (CKD-EPI2012cys) and the other using both cystatin C and serum creatinine concentrations (CKD-EPI2012Scr-cys)
  • equations were validated across the range of GFR and in relevant subgroups
• there has been data that the CKD-EPI2012Scr-cys is superior to calculations based on serum creatinine alone (3,4,5)
  • a study in Chines population ((n = 788; median age, 54 [range, 19-94] years)) concluded (5) '..CKD-EPI2012Scr-cys appeared less biased and more accurate in overall participants. Neither of the new CKD-EPI equations achieved ideal accuracy in senior participants with moderately-severely injured GFR...'
• a review states that overall, the CKD-EPICR-CYS equation had better precision and accuracy than that based on creatinine alone or CysC alone (6)
• a study by Scandrett K et al showed (7)
  • GFR estimating equations based on both cystatin C and creatinine showed better agreement with changes in measured GFR over three years than equations based on one biomarker
  • all GFR estimating equations underestimated the temporal reduction in GFR

Reference:

1. Levey AS, Stevens LA, Schmid CH, Zhang YP, Castro AF, et al.A New Equation to Estimate Glomerular Filtration Rate. Ann Intern Med 2009; 150: 604-612
2. Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2012. Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int 2012;Suppl 3: 1-150.
3. Mindikoglu AL, Dowling TC, Weir MR, Seliger SL, Christenson RH, et al.Performance of Chronic Kidney Disease Epidemiology Collaboration Creatinine-Cystatin C Equation for Estimating Kidney Function in Cirrhosis. Hepatology: 2013
4. Obiols J, Bargnoux A-S, Kuster N, Fesler P, Pieroni L, et al. Validation of a new standardized cystatin C turbidimetric assay: Evaluation of the three novel CKD-EPI equations in hypertensive patients. Clin Biochem: 2013
5. Ying Z et al. Comparisons between the 2012 New CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) Equations and Other Four Approved Equations.PLoS One. 2014; 9(1): e84688.
6. Koppe L, Klich A, Dubourg L, Ecochard R, Hadj-Aissa A. Performance of creatinine-based equations compared in older patients. Journal of Nephrology. 2013;26:716-723
7. Scandrett K et al. Accuracy of glomerular filtration rate estimation based on creatinine and cystatin C for monitoring moderate chronic kidney disease in adults: prospective, longitudinal cohort study. BMJ 2026; 392 :e085005