The MDRD formula does not reflect GFR in ESRD patients

Area of Science:

• Nephrology
• Clinical Chemistry
• Epidemiology

Background:

• The Modification of Diet in Renal Disease (MDRD) equation is standard for estimating glomerular filtration rate (GFR) using plasma creatinine.
• Its validation is limited in end-stage renal disease (ESRD) patients, where muscle mass significantly influences plasma creatinine levels.
• This study investigates the accuracy of MDRD-estimated GFR (eGFR) compared to measured GFR (mGFR) in ESRD patients initiating dialysis.

Purpose of the Study:

• To compare eGFR derived from the MDRD equation with mGFR in ESRD patients just before dialysis initiation.
• To analyze the relationship between eGFR and mGFR with mortality and muscle mass in this population.

Main Methods:

• Utilized data from 569 ESRD patients (61% male, mean age 58 years) from the Netherlands Cooperative Study on the Adequacy of Dialysis.
• Included 24-h urine collections and plasma samples at dialysis start.
• Incident dialysis patients were followed for mortality, transplantation, or study end.

Main Results:

• Mean mGFR was 6.0 mL/min/1.73 m², while mean eGFR was 6.8 mL/min/1.73 m², indicating overestimation.
• Limits of agreement between eGFR and mGFR were -4.1 to +5.6 mL/min/1.73 m².
• Higher eGFR values correlated with increased mortality (adjusted hazard ratio 1.4), and eGFR, unlike mGFR, was associated with muscle mass (P=0.001).

Conclusions:

• Plasma creatinine-based GFR estimation equations, like MDRD, are unreliable in ESRD patients.
• Muscle mass significantly affects plasma creatinine, overriding the influence of GFR in these equations.
• Clinical decisions based on eGFR in ESRD patients may be inaccurate due to confounding by muscle mass.