CystatinC in the measurement of eGFR

The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) have 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 has two newer CKD-EPI equations:
  • one using cystatin C concentration (CKD-EPI2012cys) and the other using both cystatin C and serum creatinine concentrations (CKD-EPI2012Scr-cys)
  • they validate the new equations represent an advance over currently available equations across the range of GFR and in relevant subgroups
    • the advance even holds true among participants with an extreme body-mass index of less than twenty. The two new equations even have been recommended by KDIGO 2012Clinical Practice Guidelines for the Evaluation and Management of CKD (2)
    • 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)

Reference:

• 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
• 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.
• 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
• 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
• 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.
• 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