Kidney Disease GFR Calculator

CKD-EPI 2021 Equation:

\[ eGFR = 142 \times \min(Scr/\kappa, 1)^\alpha \times \max(Scr/\kappa, 1)^{-1.200} \times 0.9938^{age} \times (1.012 \text{ if female}) \]

Estimated GFR (eGFR):

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1. What is the CKD-EPI 2021 Equation?

The CKD-EPI 2021 (Chronic Kidney Disease Epidemiology Collaboration 2021) equation estimates glomerular filtration rate (GFR) from serum creatinine, age, and sex. This updated version provides improved accuracy in GFR estimation compared to previous equations.

2. How Does the Calculator Work?

The calculator uses the CKD-EPI 2021 equation:

\[ eGFR = 142 \times \min(Scr/\kappa, 1)^\alpha \times \max(Scr/\kappa, 1)^{-1.200} \times 0.9938^{age} \times (1.012 \text{ if female}) \]

Where:

\( Scr \) — Serum creatinine (mg/dL)
\( \kappa \) — 0.7 (female) or 0.9 (male)
\( \alpha \) — -0.241 (female) or -0.302 (male)
\( age \) — Age in years
1.012 — Female multiplier

Explanation: The equation accounts for non-linear relationship between creatinine and GFR, with different coefficients for different demographic groups using updated 2021 parameters.

3. Importance of GFR Calculation

Details: Accurate GFR estimation is crucial for diagnosing chronic kidney disease, determining disease stage, monitoring progression, and guiding appropriate treatment decisions and medication dosing.

4. Using the Calculator

Tips: Enter serum creatinine in mg/dL, age in years, and select gender. All values must be valid (creatinine > 0, age between 1-120). Use fasting serum creatinine values for most accurate results.

5. Frequently Asked Questions (FAQ)

Q1: What's new in the CKD-EPI 2021 equation?
A: The 2021 version uses updated coefficients (142, -1.200, 0.9938) and refined gender multipliers based on larger, more diverse population data.

Q2: What are normal eGFR values?
A: Normal GFR is generally ≥90 mL/min/1.73m². Values between 60-89 may indicate mild reduction, while below 60 for 3+ months indicates chronic kidney disease.

Q3: When should creatinine be measured?
A: Morning fasting sample is ideal to avoid dietary influences. Avoid testing after meat-heavy meals, creatine supplements, or vigorous exercise.

Q4: Are there limitations to this equation?
A: Less accurate in extremes of age, amputees, pregnant women, severe malnutrition, and those with rapidly changing kidney function or muscle mass.

Q5: How does this compare to cystatin C equations?
A: Creatinine-based equations are more widely used, but cystatin C equations may be more accurate in elderly or those with abnormal muscle mass.