CAPA (Caucasian, Asian, Paediatric and Adult cohorts)

Cystatin C equation for children and adults

Biomarkers
Cystatin C
Validated for
1+ years
Inputs
Cystatin C, Age
Reports
mL/min/1.73 m²
Published
2014

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

Formula

eGFR=130×SCys−1.069×age−0.117−7\text{eGFR} = 130 \times \text{SCys}^{-1.069} \times \text{age}^{-0.117} - 7

As text: eGFR = 130 × SCys^(−1.069) × age^(−0.117) − 7

Constants

SymbolMeaningValue
130Base coefficient
−1.069Cystatin C exponent
−0.117Age exponent
−7Extrarenal cystatin C clearance constant
SCysSerum cystatin C (standardized) (input)mg/L
AgePatient age (input)years

How it was developed

Developed in 4,960 people: 3,495 Swedish and 763 Japanese adults and 702 Dutch and Swedish children. GFR was measured by plasma iohexol clearance (Swedish), renal inulin clearance (Japanese) and single-injection plasma inulin disappearance (Dutch); coefficients fitted in 3,164 were validated in 1,796, and the final coefficients came from all 4,960.

Clinical notes

  • Virtually assay-independent across 7 cystatin C assays standardized to ERM-DA471/IFCC
  • No sex or race terms; a tested female factor was 0.99

Limitations

  • Developed and internally validated in Swedish, Dutch and Japanese cohorts
  • Underestimates GFR in the reference range, most noticeably in children
  • Substandard P30 in adults over 80 and in Japanese adults with GFR below 30

References

  1. Grubb A, et al. Generation of a new cystatin C-based estimating equation for glomerular filtration rate by use of 7 assays standardized to the international calibrator. Clin Chem. 2014;60(7):974-86. doi:10.1373/clinchem.2013.220707

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