GFR Calculator Using CKD EPI Equation

CKD-EPI 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 Equation?

The CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation estimates glomerular filtration rate (GFR) from serum creatinine, age, and sex. This specific version provides an accurate assessment of kidney function using updated coefficients.

2. How Does the Calculator Work?

The calculator uses the CKD-EPI 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: This equation accounts for the non-linear relationship between creatinine and GFR, with optimized coefficients for different demographic groups.

3. Importance of GFR Calculation

Details: Accurate GFR estimation is essential for diagnosing chronic kidney disease, determining disease progression, and guiding appropriate clinical management and medication dosing.

4. Using the Calculator

Tips: Enter serum creatinine in mg/dL, age in years, and select gender. Ensure all values are valid (creatinine > 0, age between 1-120 years).

5. Frequently Asked Questions (FAQ)

Q1: What makes this CKD-EPI version different?
A: This version uses updated coefficients (142, -1.200, 0.9938, 1.012) that have been optimized for improved accuracy across different populations.

Q2: What are normal GFR values?
A: Normal GFR is generally ≥90 mL/min/1.73m², though values naturally decline with advancing age. Values below 60 mL/min/1.73m² for 3+ months indicate chronic kidney disease.

Q3: When is the best time to measure creatinine?
A: Morning fasting samples are preferred, though random samples are acceptable. Avoid testing shortly after protein-rich meals or strenuous physical activity.

Q4: Are there limitations to this equation?
A: The equation may be less accurate in extreme age groups, underweight or overweight individuals, amputees, pregnant women, and patients with rapidly changing kidney function.

Q5: Can this calculator be used for medication dosing?
A: While useful for estimation, precise drug dosing may require measured GFR (e.g., via iohexol or iothalamate clearance) in specific clinical situations.