Modification of Diet in Renal Disease (MDRD)

General Description

The Modification of Diet in Renal Disease (MDRD) study consisted of two randomized clinical trials that investigated whether protein restriction and control of blood pressure had an effect on the progression of chronic kidney disease (CKD). The study tested two hypotheses—that (1) a reduction in dietary protein and phosphorous intake and (2) the maintenance of blood pressure at a level below that usually recommended safely and effectively delays the progression of CKD.

In study 1, 585 patients with glomerular filtration rates (GFR) of 25-55 ml/min/1.73 m² of body-surface area were randomly assigned to a usual-protein diet or a low-protein diet (1.3 or 0.58 g of protein per kilogram of body weight per day) and to a usual- or a low-blood-pressure group (mean arterial pressure, 107 or 92 mm Hg). In study 2, 255 patients with GFR of 13 to 24 ml/min/1.73 m² were randomly assigned to the low-protein diet (0.58 g per kilogram per day) or a very-low-protein diet (0.28 g per kilogram per day) with a keto acid-amino acid supplement, and a usual- or a low-blood-pressure group (same values as those in study 1). The length of follow-up varied from 18-to-45-months, with monthly evaluations of the patients. The primary outcome was the change in GFR rate over time. The study found that among patients with moderate renal insufficiency, the slower decline in renal function that started four months after the introduction of a low-protein diet suggests a small benefit of this dietary intervention. Among patients with more severe renal insufficiency, a very-low-protein diet, as compared with a low-protein diet, did not significantly slow the progression of renal disease.

Objectives

The MDRD study aimed to investigate the effect of protein restriction and blood pressure control on the progression of disease in patients with chronic renal diseases. The study hypothesized that a reduction in dietary protein and phosphorous intake and the maintenance of blood pressure below recommended levels would delay the progression of renal disease.

Outcome Measure

The primary outcome measure used to assess renal function was the rate of change in glomerular filtration rate over time.

Criteria

The following enrollment criteria were used:

• Aged 18 to 70 years
• Serum creatinine concentration of 1.2-7.0 mg/deciliter in women and 1.4-7.0 mg/deciliter in men or a creatinine clearance of less than 70 ml/min/1.73 m² of body-surface area
• Mean arterial pressure (MAP) of 125 mm Hg or less

Glomerular filtration rate (GFR) was used to separate patients into study 1 or study 2. During a three-month base-line period, patients were deemed eligible for study 1 if their GFR was 25-55 ml/min/1.73 m², and their dietary protein intake was ≥ 0.9 g/kg of body weight per day. Patients were eligible for study 2 if their GFR was 13-24 ml/min/1.73 m², irrespective of protein intake.

Exclusion criteria are documented in the protocol

Outcome

Among patients with moderate renal insufficiency, the slower decline in renal function that started four months after the introduction of a low-protein diet suggests a small benefit of this dietary intervention. Among patients with more severe renal insufficiency, a very-low-protein diet, as compared with a low-protein diet, did not significantly slow the progression of renal disease. Overall, a low blood pressure goal was not shown to have benefit over the higher goal. Among persons with more pronounced proteinuria at baseline had a significantly slower rate of decline in GFR