GFR Calculator Without Cystatin

CKD-EPI Equation Without Cystatin:

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

Estimated GFR (eGFR):

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1. What is the CKD-EPI Creatinine Equation Without Cystatin?

The CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation without cystatin estimates glomerular filtration rate (GFR) from serum creatinine, age, and sex. This version uses only creatinine measurements without cystatin C, providing a practical alternative when cystatin C testing is unavailable.

2. How Does the Calculator Work?

The calculator uses the CKD-EPI equation without cystatin:

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

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 provides GFR estimation using only serum creatinine, making it more accessible for routine clinical practice while maintaining good accuracy.

3. Importance of eGFR Calculation

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

4. Using the Calculator

Tips: Enter serum creatinine in mg/dL, age in years, and select gender. Ensure creatinine values are greater than 0 and age is between 1-120 years for accurate results.

5. Frequently Asked Questions (FAQ)

Q1: Why use creatinine-only equation instead of combined equation?
A: The creatinine-only equation is more widely applicable when cystatin C testing is not available, making it practical for routine clinical settings.

Q2: How accurate is this equation compared to combined equations?
A: While combined equations with cystatin C may provide slightly better accuracy, the creatinine-only equation remains highly reliable for most clinical purposes.

Q3: When is creatinine measurement preferred?
A: Morning fasting samples are ideal, but random samples can be used. Avoid testing after high-protein meals or intense physical activity.

Q4: What are the limitations of this equation?
A: May be less accurate in elderly patients, those with extreme muscle mass, amputees, and individuals with rapidly changing kidney function.

Q5: Can this equation be used for medication dosing?
A: Yes, for most medications, but for drugs with narrow therapeutic windows, more precise GFR measurement may be necessary.