eGFR Calculator - Estimated Glomerular Filtration Rate
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The eGFR Calculator - Estimated Glomerular Filtration Rate is a crucial tool for evaluating kidney function and detecting kidney diseases at an early stage. It leverages blood test results, specifically serum creatinine levels, along with demographic information such as age, sex, and race, to estimate the rate at which kidneys filter blood.
Historical Background
The concept of GFR (Glomerular Filtration Rate) has long been fundamental in nephrology, providing insights into kidney health. The CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equations, developed to improve accuracy over the older MDRD (Modification of Diet in Renal Disease) study equation, are widely used today.
| Stage | GFR Value (mL/min/1.73 m²) |
|---|---|
| Normal | 90+ or above and no proteinuria |
| CKD1 | 90+ with evidence of kidney damage |
| CKD2 (Mild) | 60 to 89 with evidence of kidney damage |
| CKD3 (Moderate) | 30 to 59 |
| CKD4 (Severe) | 15 to 29 |
| CKD5 Kidney failure | less than 15 |
Calculation Formula
The GFR is estimated using formulas that incorporate serum creatinine levels, age, sex, and race. The CKD-EPI Creatinine Equation (2009) is one of the most recommended for its balance of accuracy and simplicity:
\[ \text{eGFR} = 141 \times \min\left(\frac{SCr}{k}, 1\right)^\alpha \times \max\left(\frac{SCr}{k}, 1\right)^{-1.209} \times 0.993^\text{Age} \times a \times b \]
Example Calculation
For a 35-year-old non-black male with a serum creatinine level of 1.2 mg/dL, the estimated GFR would be calculated as follows, using the CKD-EPI Creatinine Equation:
\[ \text{eGFR} \approx 141 \times \min\left(\frac{1.2}{0.9}, 1\right)^{-0.411} \times \max\left(\frac{1.2}{0.9}, 1\right)^{-1.209} \times 0.993^{35} \times 1 \times 1 \]
Importance and Usage Scenarios
GFR estimation is vital for diagnosing and managing kidney diseases, helping healthcare providers assess kidney function, detect chronic kidney disease (CKD) early, and tailor treatment plans.
Common FAQs
- What does the eGFR indicate?
- eGFR provides an estimate of kidney filtration efficiency, with lower values indicating potential kidney dysfunction.