CKiD U25 Creatinine-Cystatin C

Chronic Kidney Disease in Children study

Creatinine–cystatin C average for children and young adults with CKD

Biomarkers
Creatinine + cystatin C
Validated for
1–25 years
Inputs
Age, Sex, Height, Creatinine, Cystatin C
Reports
mL/min/1.73 m²
Published
2021

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

Formula

eGFR=eGFRcr+eGFRcys2\text{eGFR} = \frac{\text{eGFR}_{\text{cr}} + \text{eGFR}_{\text{cys}}}{2}

As text: eGFR = (U25 eGFRcr + U25 eGFRcys)/2

Constants

SymbolMeaningValue
eGFRcr\text{eGFR}_{\text{cr}}CKiD U25 Creatinine result (see CKiD U25 Creatinine equation)mL/min/1.73m²
eGFRcys\text{eGFR}_{\text{cys}}CKiD U25 Cystatin C result (see CKiD U25 Cystatin C equation)mL/min/1.73m²

How it was developed

Not fitted as a separate equation: it averages the U25 creatinine and cystatin C estimates, as the paper describes for when both are available. Both were developed in the CKiD Study, in children and young adults aged 1 to 25 years with mild to moderate CKD, with GFR measured by plasma iohexol disappearance.

Clinical notes

  • Each component uses sex- and age-specific K values
  • Built on enzymatic creatinine and IFCC-calibrated nephelometric cystatin C

Limitations

  • Not studied in people without CKD or for screening healthy patients
  • The averaged estimate has not been externally validated
  • Developed only in visits before end-stage kidney disease

References

  1. Pierce CB, Muñoz A, Ng DK, Warady BA, Furth SL, Schwartz GJ. Age- and sex-dependent clinical equations to estimate glomerular filtration rates in children and young adults with chronic kidney disease. Kidney Int. 2021;99(4):948-956. doi:10.1016/j.kint.2020.10.047
  2. Ng DK, Pierce CB. Kidney disease progression in children and young adults with pediatric CKD: Epidemiologic perspectives and clinical applications. Semin Nephrol. 2021;41(5):405-415. doi:10.1016/j.semnephrol.2021.09.002

Related equations