eGFR Calculation MDRD vs CKD EPI

Comparison of eGFR calculation using MDRD and CKD-EPI.

MDRD Equation:

\[ eGFR_{MDRD} = 175 \times Scr^{-1.154} \times Age^{-0.203} \times (0.742 \text{ if female}) \times (1.212 \text{ if Black}) \]

CKD-EPI Equation:

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

Serum Creatinine (Scr):

mg/dL

Age:

years

Gender:

Race:

MDRD eGFR:

CKD-EPI eGFR:

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1. What is eGFR Calculation MDRD vs CKD EPI?

This calculator compares two major equations for estimating glomerular filtration rate (GFR): the MDRD (Modification of Diet in Renal Disease) study equation and the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation. Both estimate kidney function from serum creatinine, age, sex, and race.

2. How Do the Calculators Work?

The calculator uses both equations:

MDRD Equation:

\[ eGFR_{MDRD} = 175 \times Scr^{-1.154} \times Age^{-0.203} \times (0.742 \text{ if female}) \times (1.212 \text{ if Black}) \]

CKD-EPI Equation:

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

Where:

\( Scr \) — Serum creatinine (mg/dL)
\( Age \) — Age in years
\( \kappa \) — 0.7 (female) or 0.9 (male)
\( \alpha \) — -0.241 (female) or -0.302 (male)

3. Comparison of MDRD and CKD-EPI Equations

MDRD: Developed in 1999, widely used but tends to underestimate GFR in healthy individuals and over-diagnose CKD at higher GFR levels.

CKD-EPI: Developed in 2009, more accurate at higher GFR levels (>60 mL/min/1.73m²), less likely to misclassify people with normal or mildly reduced 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). The calculator will display results from both equations for comparison.

5. Frequently Asked Questions (FAQ)

Q1: Which equation is better?
A: CKD-EPI is generally preferred as it's more accurate at higher GFR levels and provides better risk stratification. However, MDRD may still be used in some clinical settings.

Q2: Why do the equations give different results?
A: The equations use different mathematical formulations and coefficients. CKD-EPI has a more complex piecewise-linear structure that better handles the non-linear relationship between creatinine and GFR.

Q3: When should I use MDRD vs CKD-EPI?
A: Most current guidelines recommend CKD-EPI. MDRD may be used when comparing with historical data or in specific research contexts.

Q4: Are there population differences in accuracy?
A: Both equations perform differently across ethnic groups, ages, and body sizes. CKD-EPI generally performs better across diverse populations.

Q5: Which equation is used for drug dosing?
A: Clinical decisions and drug dosing should be based on the equation used by the laboratory and consistent with local guidelines.