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Abstract: SA-PO921

Accuracy of CKD-EPI GFR Estimating Equations According to the Difference in eGFR Using Cystatin C vs. Creatinine

Session Information

Category: CKD (Non-Dialysis)

  • 2202 CKD (Non-Dialysis): Clinical‚ Outcomes‚ and Trials


  • Wang, Yeli, Harvard University T H Chan School of Public Health, Boston, Massachusetts, United States

Group or Team Name

  • Chronic Kidney Disease-Epidemiology Collaboration

Estimated glomerular filtration rate (eGFR) using cystatin C is recommended as a confirmatory test, with eGFRcr-cys more accurate than eGFRcys. A large difference between eGFRcys and eGFRcr (eGFRdiff) likely indicates a substantial divergence from usual in the non-GFR determinants of cystatin C, creatinine or both and a potential large error in either eGFR compared to measured GFR (mGFR). However, it is not known whether eGFRcys or eGFRcr-cys is more correct. We aimed to evaluate the performance of eGFRcr, eGFRcys, and eGFRcr-cys compared to mGFR according to the magnitude of eGFRdiff.


We assessed the CKD-EPI 2021 eGFRcr and eGFRcr-cys, and 2012 eGFRcys among 4,050 participants from 12 studies included in the CKD-EPI 2021 external validation dataset. eGFRdiff was defined as eGFRcys minus eGFRcr. The negative, reference, and positive eGFRdiff categories were defined as <-15, -15 to <15, and ≥15 ml/min per 1.73 m2, respectively. We compared bias (median difference in mGFR minus eGFR), P30 (percentage of eGFR within 30% of mGFR), and concordance between eGFR and mGFR categories (<30, 30-59, 60-89, ≥90 ml/min/1.73m2) according to eGFRdiff categories.


In the overall cohort, mean (SD) GFR, age and BMI were 76.4 (29.6) ml/min/1.73m2, 57.0 (17.4) years and 26.9 (5.00) kg/m2, respectively. As reported before, eGFRcr-cys in the overall dataset had greater accuracy (higher P30 and greater concordance) than eGFRcr or eGFRcys. In the reference eGFRdiff category, all equations displayed similar performance (small differences in bias, similar P30 and concordance). In both negative and positive eGFRdiff categories, eGFRcr-cys generally had better performance (lesser bias, higher P30 and higher concordance) than eGFRcr and eGFRcys (Table). These results were consistent across subgroups of age, sex, and BMI.


In ambulatory clinical settings eGFRcr-cys is more likely to be correct than either eGFRcr or eGFRcys across sex, age, and BMI groups. Future work should evaluate whether clinician knowledge of non-GFR determinants provides more informative decision making.


  • NIDDK Support