What Is Calculated GFR in Blood Test

CKD-EPI Equation:

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

Estimated GFR (eGFR):

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1. What Is Calculated GFR in Blood Test?

Calculated GFR (Glomerular Filtration Rate) is an estimate of kidney function derived from blood test results, specifically serum creatinine levels, combined with demographic factors. It represents the rate at which fluid is filtered through the glomeruli in the kidneys.

2. How Does the Calculator Work?

The calculator uses the CKD-EPI 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 calculates estimated glomerular filtration rate from blood test parameters, accounting for the non-linear relationship between creatinine levels and kidney filtration capacity.

3. Importance of eGFR Calculation

Details: Calculated GFR is essential for assessing kidney health, detecting early kidney dysfunction, monitoring disease progression, and guiding treatment decisions for patients with or at risk of kidney disease.

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) for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What does calculated GFR measure?
A: Calculated GFR estimates how well your kidneys are filtering waste from your blood, providing a numerical value for kidney function.

Q2: Why is GFR calculation important?
A: It helps detect kidney disease early, monitor kidney function over time, and guide medication dosing for drugs cleared by the kidneys.

Q3: What are normal calculated GFR values?
A: Normal GFR is typically ≥90 mL/min/1.73m². Values below 60 for three months or more may indicate chronic kidney disease.

Q4: How often should GFR be calculated?
A: Frequency depends on individual risk factors, but typically annually for high-risk patients or as recommended by healthcare providers.

Q5: Can calculated GFR be inaccurate?
A: Yes, in certain populations like very muscular individuals, amputees, pregnant women, or those with rapidly changing kidney function.