What is the MDRD formula for measuring kidney function in azotemia?

Updated: Apr 24, 2020
  • Author: Moro O Salifu, MD, MPH, FACP; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

Another formula was derived from data collected in the Modification of Diet in Renal Disease (MDRD) study. The MDRD formula, also called the Levey formula, is now widely accepted as more accurate than the Cockcroft and Gault formula and is considered an alternative to radioisotope clearance.

Because serum creatinine levels alone cannot detect earlier stages of chronic kidney disease (CKD), the MDRD formula also takes into account the patient’s age and race. Although this formula is more accurate, it is much more difficult to calculate manually. However, software for estimating the GFR by means of the MDRD formula is available for most personal digital assistants and can be found on the Internet.

Delanaye et al have argued that the MDRD formula is inapplicable to some individuals, such as healthy individuals and patients who are anorectic or obese. [1] It has therefore been proposed that the formula should be applied with caution.

Both formulas have limitations: the Cockcroft-Gault formula is simple to use but overestimates the GFR by 10-15% because creatinine is both filtered and secreted. The MDRD formula is much more complex and has been found to underestimate GFR by 6.2% in patients with CKD and by 29% in healthy persons. [2] A third formula, the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation, is based on the same four variables as the MDRD Study formula but uses a 2-slope “spline” to model the relationship between estimated GFR and serum creatinine, and a different relationship for age, sex, and race. The National Kidney Foundation (NKF) recommends using the CKD-EPI equation to estimate GFR; a CKD-EPI calculator is available on the NKF Web site.


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