EKFC Cystatin C (2023)

Adult2023

European sex-free and race-free equation using cystatin C only

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Calculate EKFC CysC

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=107.3×(ScysC/Q)α×{1if age≤400.990age−40if age>40\text{eGFR} = 107.3 \times (S_{cysC}/Q)^{\alpha} \times \begin{cases} 1 & \text{if age} \leq 40 \\ 0.990^{\text{age}-40} & \text{if age} > 40 \end{cases}

Formula constants

SymbolDescriptionValue
107.3Base coefficient
QQMedian serum cystatin C reference
Age ≤ 50:0.83mg/L
Age > 50:0.83 + 0.005 × (age − 50)mg/L
α\alphaExponent (depends on SCysC/Q ratio)
SCysC/Q < 1:−0.322
SCysC/Q ≥ 1:−1.132
Age factorAge correction applied only when age > 40
Age ≤ 40:1 (no correction)
Age > 40:0.990^(age − 40)
ScysCS_{cysC}inputSerum cystatin Cmg/L
AgeinputPatient ageyears

Required inputs

AgeCystatin C

Validated age range

2 to 120 years

Limitations

  • Requires standardized cystatin C assay
  • More expensive than creatinine-based equations
  • Cystatin C may be affected by thyroid dysfunction, inflammation, and corticosteroids
  • Limited availability in some settings

Clinical notes

  • Sex-free AND race-free equation
  • Uses only age and cystatin C (no sex factor needed)
  • Full age spectrum equation (2-120 years)
  • Q value for cystatin C is independent of sex and ethnicity
  • Less affected by muscle mass than creatinine equations
  • Validated in diverse European, American, and African populations

References

  • [1]Pottel H, Björk J, Rule AD, et al. Cystatin C-Based Equation to Estimate GFR without the Inclusion of Race and Sex. N Engl J Med. 2023;388(4):333-343. doi:10.1056/NEJMoa2203769
  • [2]Delanaye P, Cavalier E, Pottel H, Stehlé T. New and old GFR equations: a European perspective. Clin Kidney J. 2023;16(9):1375-1383. doi:10.1093/ckj/sfad039

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