Objective: To examine the relations among proteinuria, prescribed and achieved blood pressure, and decline in glomerular filtration rate in the Modification of Diet in Renal Disease Study.
Design: 2 randomized trials in patients with chronic renal diseases of diverse cause.
Setting: 15 outpatient nephrology practices at university hospitals.
Patients: 840 patients, of whom 585 were in study A (glomerular filtration rate, 25 to 55 mliters/min.1.73 m2) and 255 were in study B (glomerular filtration rate, 13 to 24 mliters/min.1.73 m2). Diabetic patients who required insulin were excluded.
Interventions: Patients were randomly assigned to a usual blood pressure goal (target mean arterial pressure, < or = 107 mm Hg for patients < or = 60 years of age and < or = 113 mm Hg for patients > or = 61 years of age) or a low blood pressure goal (target mean arterial pressure, < or = 92 mm Hg for patients < or = 60 years of age and < or = 98 mm Hg for patients > or = 61 years of age).
Main outcome measures: Rate of decline in glomerular filtration rate and change in proteinuria during follow-up.
Results: The low blood pressure goal had a greater beneficial effect in persons with higher baseline proteinuria in both study A (P = 0.02) and study B (P = 0.01). Glomerular filtration rate declined faster in patients with higher achieved blood pressure during follow-up in both study A (r = -0.20; P < 0.001) and study B (r = -0.34; P < 0.001), and these correlations were stronger in persons with higher baseline proteinuria (P < 0.001 in study A; P < 0.01 in study B). In study A, the association between decline in glomerular filtration rate and achieved follow-up blood pressure was nonlinear (P = 0.011) and was stronger at higher mean arterial pressure. In both studies, the low blood pressure goal significantly reduced proteinuria during the first 4 months after randomization. This, in turn, correlated with a slower subsequent decline in glomerular filtration rate.
Conclusions: Our study supports the concept that proteinuria is an independent risk factor for the progression of renal disease. For patients with proteinuria of more than 1 g/d, we suggest a target blood pressure of less than 92 mm Hg (125/75 mm Hg). For patients with proteinuria of 0.25 to 1.0 g/d, a target mean arterial pressure of less than 98 mm Hg (about 130/80 mm Hg) may be advisable. The extent to which lowering blood pressure reduces proteinuria may be a measure of the effectiveness of this therapy in slowing the progression of renal disease.