How Do You Calculate GFR Glomerular Filtration Rate

GFR Calculation Formula:

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

Estimated GFR (eGFR):

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1. What Is GFR Glomerular Filtration Rate?

Glomerular Filtration Rate (GFR) is a test used to check how well the kidneys are working. Specifically, it estimates how much blood passes through the glomeruli each minute. Glomeruli are the tiny filters in the kidneys that filter waste from the blood.

2. How Does The Calculator Work?

The calculator uses the GFR calculation formula:

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

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 provides an accurate estimation of kidney function by accounting for the non-linear relationship between serum creatinine levels and actual glomerular filtration rate.

3. Importance Of GFR Calculation

Details: GFR calculation is essential for detecting kidney disease early, monitoring kidney function over time, determining the stage of chronic kidney disease, and guiding appropriate treatment decisions.

4. Using The Calculator

Tips: Enter serum creatinine in mg/dL, age in years, and select gender. Ensure all values are valid with creatinine greater than 0 and age between 1-120 years for accurate results.

5. Frequently Asked Questions (FAQ)

Q1: What Is A Normal GFR Value?
A: A normal GFR is typically 90 mL/min/1.73m² or higher. Values below 60 for three months or more may indicate chronic kidney disease.

Q2: How Often Should GFR Be Tested?
A: Testing frequency depends on individual risk factors. People with diabetes, hypertension, or family history of kidney disease should be tested annually.

Q3: Can Diet Affect GFR Results?
A: Yes, high protein intake and creatine supplements can temporarily affect creatinine levels and thus GFR calculations.

Q4: What Are The Limitations Of Estimated GFR?
A: eGFR may be less accurate in elderly individuals, those with extreme muscle mass, amputees, pregnant women, and people with rapidly changing kidney function.

Q5: When Is Measured GFR Preferred?
A: Measured GFR using clearance tests is preferred for precise medication dosing, kidney transplant evaluation, and when eGFR results are inconsistent with clinical presentation.