How to Calculate Estimated GFR from Creatinine

Estimated GFR from Creatinine:

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

Estimated GFR (eGFR):

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1. What is Estimated GFR from Creatinine?

Estimated GFR from creatinine is a calculation that estimates glomerular filtration rate (GFR) using serum creatinine levels along with demographic factors. It provides an assessment of kidney function based on creatinine metabolism and excretion.

2. How Does the Calculator Work?

The calculator uses the following 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 serum creatinine levels and glomerular filtration rate, with adjustments for age and gender differences in creatinine production and metabolism.

3. Importance of eGFR Calculation

Details: Estimating GFR from creatinine is essential for assessing kidney function, detecting early stages of chronic kidney disease, monitoring disease progression, and guiding appropriate treatment decisions and medication adjustments.

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). Use fasting serum creatinine values for most accurate results.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between this equation and CKD-EPI?
A: This equation uses different coefficients (142, -1.200, 0.9938) and gender factor (1.012) compared to CKD-EPI, providing an alternative method for GFR estimation.

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

Q3: When is the best time to measure creatinine?
A: Morning fasting samples are preferred to minimize dietary influences. Avoid testing after high-protein meals or strenuous exercise.

Q4: What factors can affect creatinine levels?
A: Muscle mass, diet, medications, hydration status, and certain medical conditions can influence serum creatinine levels independent of kidney function.

Q5: Is this equation suitable for all populations?
A: This equation may have limitations in extremes of age, body size, amputees, pregnant women, and populations with unusual muscle mass or diet patterns.