The MDRD equation is a modified, 4-variable version of the original equation (MDRD4), and has been shown to provide similar GFR results compared to its 6-variable predecessor.
This equation, based on plasma creatinine, age, sex, and race, has been validated in the MDRD study sample, and is now recommended by NKF and National Kidney Disease Education Program (NKDEP) for calculating GFR in patients with a history of CKD risk factors and a GFR <60 mL/min/1.73m2. The performance of MDRD6, and more recently the MDRD4, has been assessed in a variety of patient populations. In renal transplant patients with severe renal insufficiency (CLcr <30 mL/min/1.73m2), the MDRD6 equation was highly correlated with mean CLcr and urea clearances, less biased, and more precise than the Cockcroft-Gault (CG) equation. However, this equation was less accurate than CG in healthy subjects, diabetic patients with normal GFR (88-182 mL/min/1.73m2), and healthy potential kidney donors.
The MDRD equation should not be used in ill hospitalized patients or individuals with normal renal function and should be used with caution in children, elderly and those with extremes in muscle mass (cachectic and obese) until further performance data is available. The MDRD equations also should not be used for renal drug dose adjustment until further studies evaluating the relationship between eGFR and drug clearance/elimination are conducted.