CKD-EPI 2021 Creatinine-Cystatin C

Adult2021Recommended

Most accurate race-free equation using both creatinine and cystatin C

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Calculate CKD-EPI 2021 Cr-Cys

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

Enter all required values to see the result.

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

Formula

eGFR=135×min⁡(SCrκ,1)α×max⁡(SCrκ,1)−0.544×min⁡(SCys0.8,1)−0.323×max⁡(SCys0.8,1)−0.778×0.9961age×0.963[F]\text{eGFR} = 135 \times \min(\frac{\text{SCr}}{\kappa}, 1)^{\alpha} \times \max(\frac{\text{SCr}}{\kappa}, 1)^{-0.544} \times \min(\frac{\text{SCys}}{0.8}, 1)^{-0.323} \times \max(\frac{\text{SCys}}{0.8}, 1)^{-0.778} \times 0.9961^{\text{age}} \times 0.963^{[F]}

Formula constants

SymbolDescriptionValue
135Base coefficient
κ\kappaSex-dependent creatinine coefficient
Female:0.7mg/dL
Male:0.9mg/dL
α\alphaCreatinine exponent when SCr/κ < 1
Female:−0.219
Male:−0.144
−0.544Creatinine exponent when SCr/κ ≥ 1
0.8Cystatin C reference valuemg/L
−0.323Cystatin C exponent when SCys/0.8 < 1
−0.778Cystatin C exponent when SCys/0.8 ≥ 1
0.9961Age decay factor (base for age exponent)per year
Sex factorSex-dependent multiplier
Female:0.963
Male:1.000
ScrS_{cr}inputSerum creatininemg/dL
SCysinputSerum cystatin Cmg/L
AgeinputPatient ageyears

Required inputs

AgeSexCreatinineCystatin C

Validated age range

18 to 120 years

Limitations

  • Requires both creatinine and cystatin C measurements
  • Higher cost than single-biomarker equations
  • Less accurate in pregnancy
  • Less accurate with extremes of muscle mass

Clinical notes

  • Most accurate eGFR equation available
  • Preferred when both creatinine and cystatin C are available
  • Race-free equation developed in 2021
  • Superior accuracy compared to single-biomarker 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

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