The Modification of Diet in Renal Disease (MDRD) Study is one of the landmark papers of Nephrology. The 1994 NEJM paper describing the initial results is freely available, and there are many interesting follow-up studies using the same group as well. In my mind, the MDRD Study is important for 2 reasons:
1. It established what is currently the gold-standard formula for calculating estimated glomerular filtration rate (GFR).
2. It suggested that strict adherence to a low-protein diet did not significantly diminish the rate of renal decline in patients with advanced chronic kidney disease (CKD), which up until that time had been a major therapeutic intervention offered by many nephrologists.
Looking more closely at (1), the MDRD formula to estimate GFR: while this formula has been widely criticized, it is also the most widely used, and has significant advantages over the much simpler Cockcroft-Gault Equation. There are actually variations of the MDRD formula which yield slightly different results; the most widely-used one is the "4-variable MDRD" which takes into account serum creatinine, age, gender, and race. A "6-variable MDRD" is also used which adds in serum BUN and serum albumin.
Two major issues with the MDRD formula: first, it has been validated in CKD, but not in acute kidney injury--so even though your hospital's in-patient computer system may spit back a GFR based on the MDRD Equation, the value may be totally meaningless. Second, the MDRD seriously underestimates GFR in healthy patients with GFR > 60mL/min.
More discussion on MDRD to follow...