American Kidney Foundation eGFR Calculator

AKF eGFR 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 American Kidney Foundation eGFR Equation?

The American Kidney Foundation (AKF) eGFR equation estimates glomerular filtration rate (GFR) from serum creatinine, age, and sex. This equation provides a reliable assessment of kidney function using standardized coefficients optimized for clinical accuracy.

2. How Does the Calculator Work?

The calculator uses the AKF eGFR 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 the non-linear relationship between creatinine and GFR, with gender-specific coefficients that provide accurate estimates across different demographic groups.

3. Importance of eGFR Calculation

Details: Accurate GFR estimation is essential for diagnosing chronic kidney disease, determining disease progression, staging kidney function, and guiding appropriate medication dosing and treatment decisions.

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) for accurate results.

5. Frequently Asked Questions (FAQ)

Q1: What makes the AKF equation different from other eGFR equations?
A: The AKF equation uses optimized coefficients (142, -1.200, 0.9938) and gender-specific parameters to provide reliable estimates across diverse populations.

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

Q3: When is the best time to measure serum creatinine?
A: Morning fasting samples are preferred, but random samples are acceptable. Avoid testing immediately after high-protein meals or intense physical activity.

Q4: Are there limitations to the AKF eGFR equation?
A: This equation may be less accurate in extreme age groups, individuals with very high or low muscle mass, amputees, pregnant women, and those with rapidly changing kidney function.

Q5: Can this calculator be used for medication dosing adjustments?
A: While useful for screening and monitoring, for precise drug dosing in critical situations, measured GFR methods may be necessary for certain patient populations.