CKD-EPI 2012 Cystatin C

Chronic Kidney Disease Epidemiology Collaboration

Cystatin C–only equation for adults, with no race coefficient

Biomarkers
Cystatin C
Validated for
18+ years
Inputs
Age, Sex, Cystatin C
Reports
mL/min/1.73 m²
Published
2012

The eGFR guide explains which equation the calculator suggests and indexed and absolute GFR.

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]}

As text: eGFR = 133 × min(SCys/0.8,1)^(-0.499) × max(SCys/0.8,1)^(-1.328) × 0.9962^Age × (0.932 if female)

Constants

SymbolMeaningValue
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 — full-precision coefficient from Inker 2021 Table 2 (printed as 0.996 in the 2012 paper)per year
Sex factorSex-dependent multiplier
Female: 0.932
Male: 1.000
SCysSerum cystatin C (input)mg/L
AgePatient age (input)years

How it was developed

Developed by the CKD-EPI collaboration in 5,352 participants from 13 studies, with GFR measured as urinary iothalamate clearance. It was validated externally in 1,119 participants from 5 other studies that measured GFR with other filtration markers.

Clinical notes

  • Built on cystatin C traceable to IFCC/IRMM reference material (ERM-DA471)
  • Carried into CKD-EPI 2021 unchanged as the current cystatin C equation
  • Cystatin C is less affected by muscle mass and diet than creatinine

Limitations

  • Not developed or validated in transplant recipients
  • No development data from people with markedly reduced muscle mass or malnutrition
  • Cystatin C may be affected by adiposity, smoking, thyroid dysfunction, glucocorticoids, inflammation

References

  1. Inker LA, Schmid CH, Tighiouart H, et al. Estimating glomerular filtration rate from serum creatinine and cystatin C. N Engl J Med. 2012;367(1):20-29. doi:10.1056/NEJMoa1114248
  2. 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
  3. 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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