Hypertension and non-insulin-dependent diabetes mellitus (NIDDM) are two major risk factors for end-stage renal failure. The value of microalbuminuria (urinary albumin excretion [UAE]: 30-300 mg/24 h) as an indicator of the glomerular filtration rate (GFR) is not known in these patients.
Methods: The relationships between microalbuminuria and GFR in subjects with NIDDM and hypertension were studied cross-sectionally (Study I) and longitudinally (Study II).
Results: In study I, 205 NIDDM subjects with hypertension (151 with normoalbuminuria [UAE < 30 mg/24 h] and 54 with microalbuminuria) were studied. The GFR of subjects with normoalbuminuria (97 +/- 30 ml/min) (mean +/- SD), and microalbuminuria (97 +/- 27 ml/min; NS) were similar. Study II examined 51 of the subjects with normoalbuminuria and 21 with microalbuminuria 22 months (range 13-57) later. The GFR of subjects with microalbuminuria (-10 +/- 19 ml/min) declined more than in those with normoalbuminuria (+4 +/- 17 ml/min; Student's t-test: p = 0.0022). The predictive value of microalbuminuria for a drop in GFR was independent of the antihypertensive treatment used, the follow-up time, or changes in UAE. The only variable linked to GFR loss in subjects with microalbuminuria was an increase in diastolic blood pressure (p = 0.0298).
Conclusion: Microalbuminuria is a risk factor for a drop in GRF in NIDDM subjects with hypertension, and a reduction in blood pressure is the only effective way to prevent a loss of GFR in subjects with microalbuminuria.