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Cystatin C-based CrCl Equation:
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Cystatin C-based creatinine clearance provides an alternative method for estimating kidney function using cystatin C levels instead of traditional serum creatinine. Cystatin C is less influenced by muscle mass, age, and diet compared to creatinine, making it a potentially more reliable marker in certain populations.
The calculator uses the Cystatin C-based equation:
Where:
Explanation: This equation estimates creatinine clearance based on cystatin C levels, which is particularly useful when serum creatinine measurements may be unreliable due to factors like altered muscle mass or diet.
Details: Cystatin C-based calculations are valuable in patients with abnormal muscle mass, elderly patients, and those with conditions that affect creatinine production. It provides a complementary assessment of kidney function alongside traditional creatinine-based methods.
Tips: Enter cystatin C concentration in mg/L, age in years, and select gender. All values must be valid (cystatin C > 0, age between 1-120 years).
Q1: Why use cystatin C instead of serum creatinine?
A: Cystatin C is less affected by muscle mass, age, gender, and diet, making it more reliable in populations where these factors may confound creatinine-based estimates.
Q2: When is cystatin C particularly useful?
A: In elderly patients, patients with muscle wasting, obesity, malnutrition, or those with rapidly changing muscle mass.
Q3: What are normal cystatin C levels?
A: Normal cystatin C levels are typically between 0.5-1.0 mg/L, though reference ranges may vary by laboratory.
Q4: Are there limitations to cystatin C measurement?
A: Cystatin C can be affected by thyroid dysfunction, corticosteroid use, and inflammation. It may also be more expensive than creatinine testing.
Q5: Should this replace traditional creatinine-based eGFR?
A: It serves as a complementary test rather than a replacement, providing additional information when creatinine-based estimates may be unreliable.