1. Can Cystatin C be measured in my urine?
No. Unlike creatinine, Cystatin C is reabsorbed from the glomerular filtrate and then metabolized in the kidneys. Under normal conditions, Cystatin C is not found in detectable levels in excreted urine.
2. How else can my GFR be determined?
The GFR cannot be measured directly. The best method for estimating the GFR (eGFR) is a procedure called an "inulin clearance." It is not routinely used, however, because it is expensive and intrusive. It involves introducing a fluid containing the compound inulin into your veins (IV – intravenous infusion), collecting timed urines over a period of hours, and measuring the inulin in these specimens. Other clearance methods using radioactive markers have similar drawbacks. The National Kidney Foundation is now recommending several different predictive equations that are used in combination with serum creatinine levels to calculate the eGFR.
