EKFC Combined (Creatinine-Cystatin C)

Adult2023

Most accurate European equation combining creatinine and cystatin C

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Calculate EKFC Cr-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

eGFRcombined=eGFREKFC-Cr+eGFREKFC-CysC2\text{eGFR}_{\text{combined}} = \frac{\text{eGFR}_{\text{EKFC-Cr}} + \text{eGFR}_{\text{EKFC-CysC}}}{2}

Formula constants

SymbolDescriptionValue
eGFREKFC-Cr\text{eGFR}_{\text{EKFC-Cr}}EKFC Creatinine result (see EKFC Creatinine equation)mL/min/1.73m²
eGFREKFC-CysC\text{eGFR}_{\text{EKFC-CysC}}EKFC Cystatin C result (see EKFC Cystatin C equation)mL/min/1.73m²
Q (creatinine)Median serum creatinine of healthy persons (rescaling factor)
Female (>25 y):0.70 (62 μmol/L)mg/dL
Male (>25 y):0.90 (80 μmol/L)mg/dL
2–25 y:ln(Q) polynomial in age (Pottel 2021, Figure 1)mg/dL
Q (cystatin C)Median serum cystatin C reference
Age ≤ 50:0.83mg/L
Age > 50:0.83 + 0.005 × (age − 50)mg/L
ScrS_{cr}inputSerum creatininemg/dL
ScysCS_{cysC}inputSerum 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
  • Requires standardized assays for both biomarkers
  • Cystatin C component validated in adults only (≥18 years)

Clinical notes

  • Most accurate European equation when both biomarkers available
  • Simple average of EKFC-Creatinine and EKFC-Cystatin C
  • Race-free equation
  • Validated in adult cohorts (≥18 years) — the cystatin C component has no pediatric validation
  • Close to 90% of results within ±30% of measured GFR
  • Recommended when both biomarkers are measured

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]Pottel H, Björk J, Courbebaisse M, et al. Development and validation of a modified full age spectrum creatinine-based equation to estimate glomerular filtration rate. Ann Intern Med. 2021;174(2):183-191. doi:10.7326/M20-4366
  • [3]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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