EKFC Cystatin C (2023)
Adult2023
European sex-free and race-free equation using cystatin C only
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
Formula constants
| Symbol | Description | Value |
|---|---|---|
107.3 | Base coefficient | |
| Median serum cystatin C reference | Age ≤ 50:0.83mg/L Age > 50:0.83 + 0.005 × (age − 50)mg/L | |
| Exponent (depends on SCysC/Q ratio) | SCysC/Q < 1:−0.322 SCysC/Q ≥ 1:−1.132 | |
Age factor | Age correction applied only when age > 40 | Age ≤ 40:1 (no correction) Age > 40:0.990^(age − 40) |
| input | Serum cystatin C | mg/L |
Ageinput | Patient age | years |
Required inputs
AgeCystatin C
Validated age range
18 to 120 years
Limitations
- Requires standardized cystatin C assay (ERM-DA471/IFCC)
- No pediatric cohorts in the validation study (all patients ≥18 years)
- More expensive than creatinine-based equations
- Cystatin C may be affected by thyroid dysfunction, inflammation, and corticosteroids
Clinical notes
- Sex-free AND race-free equation
- Uses only age and cystatin C (no sex factor needed)
- Q rescaling factor derived without race or sex terms (Q = 0.83 mg/L; age-adjusted after 50)
- Less affected by muscle mass than creatinine equations
- Validated in adult European, American, and African cohorts (all ≥18 years)
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