National Kidney Function eGFR Calculator

NKF 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 NKF eGFR Calculator?

The National Kidney Function (NKF) eGFR calculator estimates glomerular filtration rate (GFR) from serum creatinine, age, and sex. This equation provides a standardized method for assessing kidney function in clinical practice.

2. How Does the Calculator Work?

The calculator uses the NKF 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 different coefficients for males and females to improve accuracy.

3. Importance of eGFR Calculation

Details: Accurate GFR estimation is essential for detecting early kidney dysfunction, monitoring disease progression, and adjusting medication dosages based on renal function.

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 NKF equation different from other eGFR formulas?
A: The NKF equation uses specific coefficients optimized for general population screening and incorporates age and gender adjustments for improved accuracy.

Q2: What are the reference ranges for eGFR?
A: Normal eGFR is typically ≥90 mL/min/1.73m². Values between 60-89 may indicate mild reduction, while persistent values below 60 suggest chronic kidney disease.

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

Q4: What are the limitations of this equation?
A: The equation may be less accurate in elderly patients, those with extreme body weights, amputees, pregnant women, and individuals with rapidly changing kidney function.

Q5: Can this calculator be used for medication dosing?
A: While useful for screening, specific drug dosing may require more precise GFR measurements in certain clinical situations.