1. How can my GFR be determined?
Direct measurement of the GFR is complicated and requires experienced personnel. The most commonly used method for determining the GFR is the creatinine clearance method mentioned above. However, this is prone to errors of urine collection as well as to problems with testing methods. The best method for determining the GFR is a procedure called an “inulin clearance.” It is not routinely used, however, because it is expensive and awkward. It involves introducing a fluid containing the marker molecule inulin (NOT insulin) into your veins (IV – intravenous infusion) and then collecting timed urines over a period of hours. The urine volumes are noted and the inulin in each sample is measured to allow determination of the GFR. Other methods of determining GFR use radioactive markers and 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. The use of these equations may become widespread as doctors learn how to use them to monitor their patients.
