How to Calculate eGFR From Serum Creatinine

MDRD Equation:

\[ eGFR = 175 \times (SCr)^{-1.154} \times Age^{-0.203} \times Gender \times Race \]

Serum Creatinine (SCr):

mg/dL

Age:

years

Gender:

Race:

Estimated GFR (eGFR):

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1. What is the MDRD Equation?

The MDRD (Modification of Diet in Renal Disease) equation estimates glomerular filtration rate (GFR) from serum creatinine, age, sex, and race. It was developed to provide a more accurate assessment of kidney function in patients with chronic kidney disease.

2. How Does the Calculator Work?

The calculator uses the MDRD equation:

\[ eGFR = 175 \times (SCr)^{-1.154} \times Age^{-0.203} \times Gender \times Race \]

Where:

\( SCr \) — Serum creatinine (mg/dL)
\( Age \) — Age in years
\( Gender \) — 0.742 for female, 1.0 for male
\( Race \) — 1.212 for Black, 1.0 for other races

Explanation: The equation uses serum creatinine, age, gender, and race to estimate kidney function, with different coefficients accounting for demographic variations.

3. Importance of eGFR Calculation

Details: Accurate GFR estimation is essential for diagnosing chronic kidney disease, monitoring disease progression, and adjusting medication dosages based on kidney function.

4. Using the Calculator

Tips: Enter serum creatinine in mg/dL, age in years, select gender and race. All values must be valid (creatinine > 0, age between 1-120 years).

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between MDRD and CKD-EPI equations?
A: MDRD is more accurate in patients with established CKD, while CKD-EPI performs better at higher GFR levels and is less likely to misclassify individuals with normal or mildly reduced kidney function.

Q2: What are the limitations of the MDRD equation?
A: The equation may be less accurate in elderly patients, those with normal kidney function, pregnant women, and individuals with extremes of body size or muscle mass.

Q3: When is the MDRD equation most appropriate?
A: The MDRD equation is particularly useful for monitoring patients with known chronic kidney disease and for staging CKD severity.

Q4: How does diet affect serum creatinine levels?
A: High protein intake, particularly from meat, can temporarily increase serum creatinine levels, potentially affecting eGFR calculations.

Q5: Should MDRD be used for all patient populations?
A: For specific populations like children, pregnant women, or those with rapidly changing kidney function, alternative methods of GFR estimation may be more appropriate.