Calculator: Glomerular filtration rate estimation (eGFR) by CKiD U25 equations with creatinine and/or cystatin C in children and adults ≤25 years old (2021)

Input

Age
Sex	Female
	Male
Height
Serum creatinine
Serum cystatin C

Results

Important: Inputs must be complete to perform calculation.


eGFR by creatinine		mL/min/1.73 m²
eGFR by cystatin C		mL/min/1.73 m²
Average eGFR		mL/min/1.73 m²

Decimal precision

Notes

Creatinine levels must be based on an enzymatic creatinine assay, which is the method used in most contemporary laboratories. If serum creatinine is measured by the Jaffe assay, GFR can be estimated by the original Schwartz equation.^[1]
Cystatin C levels should be derived using an assay that is calibrated against IFCC reference material.
This calculator can be used to estimate GFR using either creatinine or cystatin C alone or both values. The average of the GFR estimates determined with creatinine and cystatin C, respectively, is more accurate and precise than either of the two single-marker estimates.^[2]
This calculator is appropriate for use in children ages 1 to 25 years of age with childhood-onset chronic kidney disease.
All of these equations estimate GFR rather than measuring it directly or indirectly. The CKiD U25 estimating equations become less accurate as GFR increases, particularly if GFR >75 mL/min/1.73 m².^[3]
CKiD: Chronic Kidney Disease in Children study; U25: under 25 years of age; IFCC: International Federation of Clinical Chemistry and Laboratory Medicine.

Equations used

eGFR_by_creatinine = K_Creat * (Height / 100) / Serum_creatinine

eGFR_by_cystatin_C = K_CysC / Serum_cystatin_C

Average_eGFR = (eGFR_by_creatinine + eGFR_by_cystatin_C) / 2

Calculation details and variables

Age-based variables are assigned values by this ordered logic:
- If Age is <12 years and Sex is Female, K_Creat = 36.1 * 1.008^{(Age - 12)} and K_CysC = 79.9 * 1.004^{(Age - 12)}
- Else if Age is <12 years and Sex is Male, K_Creat = 39 * 1.008^{(Age - 12)} and K_CysC = 87.2 * 1.011^{(Age - 15)}
- Else if Age is <15 years and Sex is Female, K_Creat = 36.1 * 1.023^{(Age - 12)} and K_CysC = 79.9 * 0.974^{(Age - 12)}
- Else if Age is <15 years and Sex is Male, K_Creat = 39 * 1.045^{(Age - 12)} and K_CysC = 87.2 * 1.011^{(Age - 15)}
- Else if Age is <18 years and Sex is Female, K_Creat = 36.1 * 1.023^{(Age - 12)} and K_CysC = 79.9 * 0.974^{(Age - 12)}
- Else if Age is <18 years and Sex is Male, K_Creat = 39 * 1.045^{(Age - 12)} and K_CysC = 87.2 * 0.960^{(Age - 15)}
- Else if Age is ≤25 years and Sex is Female, K_Creat = 41.4 and K_CysC = 68.3
- Else if Age is ≤25 years and Sex is Male, K_Creat = 50.8 and K_CysC = 77.1

References

Only digits 0 to 9 and a single decimal point (".") are acceptable as numeric inputs. Attempted input of other characters into a numeric field may lead to an incorrect result.

Information on this page may not appear correctly if printed.

All information contained in and produced by the EBMcalc system is provided for educational purposes only. This information should not be used for the diagnosis or treatment of any health problem or disease. THIS INFORMATION IS NOT INTENDED TO REPLACE CLINICAL JUDGMENT OR GUIDE INDIVIDUAL PATIENT CARE IN ANY MANNER. Click here for full notice and disclaimer.

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Calculator: Glomerular filtration rate estimation (eGFR) by CKiD U25 equations with creatinine and/or cystatin C in children and adults ≤25 years old (2021)