STABLE GLOMERULAR-FILTRATION RATE IN NORMOTENSIVE IDDM PATIENTS WITH STABLE MICROALBUMINURIA - A 5-YEAR PROSPECTIVE-STUDY

OBJECTIVE - To investigate the long-term course of glomerular filtrati on rate (GFR) in IDDM patients with microalbuminuria in order to ident ify patients with stable or declining kidney function over a 5-year st udy. RESEARCH DESIGN AND METHODS - Forty normotensive (129 +/- 11/80 /- 8 mmHg) IDDM patients with persistent microalbuminuria (mean urinar y albumin excretion [UAE] 84 mg/24 h [range 30-300]) were followed pro spectively for 5 years of clinical examinations that included the meas urement of GFR (Cr-51-Iabeled EDTA clearance) at least once a year. Th e mean GFR at baseline was 120 +/- 18 ml . min(-1). 1.73 m(-2). RESULT S - Using multiple regression analysis, the rate of decline in GFR was independently correlated to onset of diabetic nephropathy (P < 0.001) and systolic blood pressure (sBP) at baseline (P < 0.05). Increase in UAE was correlated to the mean HbA(1c) during the observation period. Out of 40 patients, 14 progressed to diabetic nephropathy (UAE >300 m g/24 h). These patients had a significant reduction in GFR (mean -2.2 +/- 3.8 ml . min(-1). year(-1); P = 0.05), while GFR remained stable i n the remaining 26 patients with nonprogressive microalbuminuria (chan ge in GFR 0.5 +/- 2.1 ml . min(-1). year(-1); NS). The difference in t he rate of decline of GFR was significant (mean 2.7 ml . min(-1). year (-1); P < 0.05). CONCLUSIONS - Normotensive IDDM patients with nonprog ressive microalbuminuria have a stable GFR Progression of UAE to diabe tic nephropathy heralds a progressive loss of kidney function. Efforts should be made to prevent the progression from microalbuminuria to di abetic nephropathy in every IDDM patient with microalbuminuria.