The Modification of Diet in Renal Disease Study

Overview

The Modification of Diet in Renal Disease Trial is a multicenter randomized clinical trial for men and women aged 18-70 years with chronic renal disease who are not on dialysis and who have not had a kidney transplant. Study participants are randomized in a 2 × 2 factorial design to diets containing different amounts of protein and phosphorus and to two levels of blood pressure control. The prescribed modifications differ depending on the level of a patient's kidney function. The primary outcome variable to compare diet or blood pressure groups is each patient's slope (or the change) in glomerular filtration rate (GFR) with time.

Selection of patients is conducted in two periods: a screening period for initial determination of eligibility and a 3-month baseline period. The baseline period is used to instruct patients about study procedures; to assess GFR and dietary protein intake; and to control blood pressure according to standard medical practice. GFR, dietary protein, and urinary protein must meet the eligibility criteria at the end of the baseline period before an individual can be randomized. Two different strata or studies are used depending on the level of an individual's GFR at the end of the baseline period. Study A is for individuals with a GFR from 25 to 55 ml/min/1.73 m\^2 and a usual dietary protein intake of at least 0.90 g/kg/day, where kg are standard body weight. Study B is for persons with a baseline GFR from 13 to 24 ml/min/1.73 m\^2 and no specification of protein intake. Individuals who are randomized in the trial are prescribed one of three diets and one of two target mean arterial blood pressure goals (MAP). MAP is a weighted average of the diastolic and systolic blood pressures (two-thirds diastolic plus one-third systolic). The goals depend on the person's age. The moderate goal of 107 mm Hg is equivalent to a blood pressure of 140/90 mm Hg, the usual limits of normal blood pressure. The low-MAP goal of 92 mm Hg is a more strict level of control than usually achieved, equivalent to, for example, 125/75 mm Hg.