1. What is the Cystatin C GFR Equation?

The Cystatin C equation estimates glomerular filtration rate (GFR) from serum cystatin C levels. Cystatin C is an alternative marker of kidney function that may be more accurate than creatinine in certain populations.

2. How Does the Calculator Work?

The calculator uses the Cystatin C equation:

Where:

• \( Cystatin\ C \) — Serum cystatin C concentration (mg/L)

Explanation: The equation shows an inverse relationship between cystatin C levels and GFR, with higher cystatin C values indicating lower kidney function.

3. Importance of Cystatin C Measurement

Details: Cystatin C is less influenced by muscle mass, diet, or age compared to creatinine, making it particularly useful in elderly patients, those with malnutrition, or amputees.

4. Using the Calculator

Tips: Enter cystatin C value in mg/L. The value must be valid (greater than 0).

5. Frequently Asked Questions (FAQ)

Q1: When should cystatin C be used instead of creatinine?
A: Consider cystatin C when creatinine-based estimates may be unreliable (extremes of age, muscle mass, or diet).

Q2: What are normal cystatin C values?
A: Typical reference range is 0.5-1.2 mg/L in healthy adults, but varies by laboratory.

Q3: Are there limitations to cystatin C measurement?
A: Cystatin C can be affected by thyroid dysfunction, glucocorticoid therapy, and inflammation.

Q4: Is cystatin C more expensive than creatinine?
A: Yes, cystatin C testing is typically more expensive than creatinine measurement.

Q5: Can cystatin C and creatinine be combined?
A: Yes, some equations combine both markers for potentially more accurate GFR estimation.