eGFR Calculator
Using the 2012 CKD-EPI Creatinine-Cystatin C Formula — Assess Your Kidney Function
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Formula Details (2012 CKD-EPI Creatinine-Cystatin C)
eGFR = A × (Scr/B)C × (Scys/0.8)D × 0.995Age × (1.08 if Black)
Scr in mg/dL, Scys in mg/L.
| Sex | SCr (mg/dL) | Scys (mg/L) | Parameters | |||
|---|---|---|---|---|---|---|
| A | B | C | D | |||
| Female | ≤ 0.7 | ≤ 0.8 | 130 | 0.7 | -0.248 | -0.375 |
| > 0.8 | 130 | 0.7 | -0.248 | -0.711 | ||
| > 0.7 | ≤ 0.8 | 130 | 0.7 | -0.601 | -0.375 | |
| > 0.8 | 130 | 0.7 | -0.601 | -0.711 | ||
| Male | ≤ 0.9 | ≤ 0.8 | 135 | 0.9 | -0.207 | -0.375 |
| > 0.8 | 135 | 0.9 | -0.207 | -0.711 | ||
| > 0.9 | ≤ 0.8 | 135 | 0.9 | -0.601 | -0.375 | |
| > 0.8 | 135 | 0.9 | -0.601 | -0.711 | ||
About eGFR and the 2012 CKD-EPI Creatinine-Cystatin C Formula
What is Estimated Glomerular Filtration Rate (eGFR)?
The Estimated Glomerular Filtration Rate (eGFR) is a key indicator of kidney function. It measures how well your kidneys are filtering waste products from your blood, specifically estimating the volume of blood filtered by the glomeruli (tiny filters in the kidneys) per minute. This value is standardized to a body surface area of 1.73m² (mL/min/1.73m²).
The CKD-EPI 2012 Creatinine-Cystatin C Formula
This calculator uses the 2012 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) Creatinine-Cystatin C equation. This combined formula utilizes serum creatinine (SCr), serum cystatin C (Scys), age, sex, and a race coefficient (for individuals identifying as Black) to provide a more robust estimation of GFR. By incorporating two different kidney filtration markers (creatinine and cystatin C), this equation aims to improve accuracy across a wider range of individuals and clinical scenarios compared to equations based on a single marker. Cystatin C is less affected by muscle mass and diet than creatinine, while creatinine is widely available and standardized. The race coefficient (1.08 for Black individuals) was included in the original 2012 formula to account for observed population differences in GFR at given marker levels, though the use of race in GFR estimation is a subject of ongoing discussion and refinement in newer equations.
Clinical Significance of eGFR Values (Based on KDIGO Guidelines) for Kidney Function
eGFR values are used to classify the stage of chronic kidney disease (CKD) and to guide treatment decisions. The classification is based on the estimated GFR and is outlined in the KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. The stages are:
- Stage G1: Normal or high kidney function (eGFR ≥ 90)
- Stage G2: Mildly decreased kidney function (eGFR 60-89)
- Stage G3a: Mild to moderately decreased kidney function (eGFR 45-59)
- Stage G3b: Moderate to severely decreased kidney function (eGFR 30-44)
- Stage G4: Severely decreased kidney function (eGFR 15-29)
- Stage G5: Kidney failure (eGFR < 15)
If other evidence of kidney damage (e.g., proteinuria) is present, it may indicate chronic kidney disease.
References:
- Inker LA, Schmid CH, Tighiouart H, et al. Estimating glomerular filtration rate from serum creatinine and cystatin C. N Engl J Med 2012; 367:20-29. (This paper introduces the 2012 CKD-EPI equations using creatinine, cystatin C, or both. This calculator uses the combined creatinine-cystatin C version.)
- Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int Suppl. 2013;3(1):1-150. (General guidelines for interpreting eGFR)
Frequently Asked Questions (FAQ) about eGFR & Kidney Function (Creatinine-Cystatin C Based)
eGFR stands for Estimated Glomerular Filtration Rate, a key measure of kidney function. This calculator uses the 2012 CKD-EPI Creatinine-Cystatin C formula, which combines two blood markers: serum creatinine (SCr) and serum cystatin C (Scys). Your age, sex, and race (with a specific coefficient for Black individuals) are also factored in. Using both markers can provide a more accurate eGFR estimate than using either one alone, as they are affected differently by factors like muscle mass and diet.
This eGFR calculator utilizes the 2012 CKD-EPI Creatinine-Cystatin C formula because it is designed to provide a more robust and often more accurate estimation of GFR by incorporating two different biomarkers (serum creatinine and serum cystatin C). This can be particularly beneficial in diverse populations and in individuals where single-marker equations might be less precise. It also includes adjustments for age, sex, and race as per the 2012 guidelines.
This eGFR calculator, using the 2012 CKD-EPI Creatinine-Cystatin C formula, differs from single-marker calculators (e.g., creatinine-only or cystatin C-only) by using both serum creatinine and serum cystatin C values. The rationale is that combining markers can buffer against the limitations of each individual marker (e.g., creatinine's sensitivity to muscle mass, cystatin C's potential variations with inflammation). This often leads to a more stable and accurate GFR estimation across a broader range of people. Additionally, this 2012 formula includes a race coefficient for Black individuals, which newer single-marker (like 2021 CKD-EPI creatinine) formulas have omitted.
No, this specific eGFR calculator and the 2012 CKD-EPI Creatinine-Cystatin C formula are validated and intended for use in adults (individuals aged 18 years and older). They are not designed for pediatric use. Assessing kidney function during pregnancy or in children requires specialized evaluation and different GFR estimation formulas.
The 2012 CKD-EPI Creatinine-Cystatin C formula includes a race coefficient (specifically for individuals identifying as Black) because, at the time of its development, studies showed differences in average measured GFR between racial groups even with similar levels of creatinine and other factors. The coefficient was an attempt to improve accuracy for this population group. However, the use of race in GFR estimation is a complex and evolving topic. Newer GFR equations, such as the 2021 CKD-EPI creatinine and creatinine-cystatin C equations, have been developed and validated without a race variable to promote health equity.
Serum Creatinine (SCr) is a waste product from muscle metabolism. Healthy kidneys filter it from the blood. Serum Cystatin C (Scys) is a protein produced by all cells with a nucleus. It's also filtered by the kidneys. Levels of both SCr and Scys in the blood can indicate how well the kidneys are working. Using both together in the 2012 CKD-EPI Creatinine-Cystatin C formula can provide a more comprehensive assessment of kidney function.
The results provided by this eGFR calculator are for informational purposes only and cannot replace professional medical advice, diagnosis, or treatment for your kidney function.
Calculation results are based on the CKD-EPI 2012 Creatinine-Cystatin C formula, which has its limitations and may not be suitable for all individuals (e.g., age under 18, pregnancy, significantly abnormal muscle mass, extreme diets, acute changes in renal function, or issues with serum creatinine or serum cystatin C measurement). The inclusion of a race coefficient is based on the original 2012 publication and may not be appropriate in all contexts or for all individuals.
Any decisions regarding your health status should be made after consulting a qualified healthcare professional. Do not self-diagnose or adjust treatment plans based solely on the results from this eGFR calculator.
This website assumes no liability for any direct or indirect loss arising from the use of the information provided by this GFR calculator tool.