CKD-EPI 2021 Cystatin C

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Latest race-free cystatin C equation from CKD-EPI group

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Calculate CKD-EPI 2021 CysC

Enter the values required by this equation to estimate the result.

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For educational and clinical reference use. Interpret results in clinical context.

Formula

eGFR=133×min⁡(SCys0.8,1)−0.499×max⁡(SCys0.8,1)−1.328×0.9962age×0.932[F]\text{eGFR} = 133 \times \min(\frac{\text{SCys}}{0.8}, 1)^{-0.499} \times \max(\frac{\text{SCys}}{0.8}, 1)^{-1.328} \times 0.9962^{\text{age}} \times 0.932^{[F]}

Formula constants

SymbolDescriptionValue
133Base coefficient
0.8Cystatin C reference valuemg/L
−0.499Exponent when SCys/0.8 < 1
−1.328Exponent when SCys/0.8 ≥ 1
0.9962Age decay factor (base for age exponent)per year
Sex factorSex-dependent multiplier
Female:0.932
Male:1.000
SCysinputSerum cystatin Cmg/L
AgeinputPatient ageyears

Required inputs

AgeSexCystatin C

Validated age range

18 to 120 years

Limitations

  • Requires standardized cystatin C assay
  • More expensive than creatinine-based equations
  • Limited availability in some settings
  • Less validation than creatinine-based equations

Clinical notes

  • Latest race-free cystatin C equation from CKD-EPI group
  • Recommended for confirmatory testing
  • Less affected by muscle mass than creatinine
  • Requires standardized cystatin C assay
  • More expensive than creatinine-based equations

References

  • [1]Inker LA, Eneanya ND, Coresh J, et al. New creatinine- and cystatin C-based equations to estimate GFR without race. N Engl J Med. 2021;385(19):1737-1749. doi:10.1056/NEJMoa2102953
  • [2]KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int. 2024;105(4S):S117-S314. doi:10.1016/j.kint.2023.10.018
  • [3]Delgado C, Baweja M, Crews DC, et al. A unifying approach for GFR estimation: recommendations of the NKF-ASN Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Disease. Am J Kidney Dis. 2022;79(2):268-288. doi:10.1053/j.ajkd.2021.08.003

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