The most commonly used equation for calculating the eGFR, and the one currently recommended by the National Kidney Foundation (NKF) for general use, is called the MDRD (Modification of Diet in Renal Disease Study) equation. It requires a person's serum creatinine, age, and assigned values based upon sex and race.
According to the NKF, as of January 2013, many large commercial clinical laboratories have changed from using the MDRD equation for eGFR reporting to a slightly different one that uses the same factors, the CKD-EPI equation, published in 2009. The results reported using one equation versus the other will not be identical but should give the health practitioner similar information.
Researchers are also evaluating the usefulness of a variety of other equations to estimate GFR that combine tests such as a creatinine, BUN, and/or cystatin C.
The best method for directly determining the glomerular filtration rate (GFR) is a procedure called an "inulin clearance." It involves introducing a fluid containing the marker molecule inulin (NOT insulin) into your veins (IV – intravenous infusion) and then collecting timed urine samples over a period of hours. The urine volumes are noted and the inulin in each sample is measured to allow determination of the GFR. This test and other methods of determining GFR, such as those that use radioactive markers, are not routinely ordered and are primarily performed in research settings.
This article was last reviewed on October 25, 2013. | This article was last modified on April 3, 2014.
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