Microalbuminuria in type I diabetic patients. Prevalence and clinical characteristics.

Abstract

To estimate the prevalence of microalbuminuria, overnight urinary albumin excretion rate (AER) greater than or equal to 30 and less than or equal to 250 micrograms/min, in a large sequential sample of nonhypertensive insulin-dependent (type I) diabetic patients attending hospital diabetic clinics, to identify micro- and normoalbuminuric patients in this sample for subsequent intervention and natural history follow-up studies, and to compare the clinical characteristics of the micro- and normoalbuminuric patients identified. Screening was conducted in two phases. In phase 1, all eligible patients were asked to provide an early morning urine specimen for measurement of albumin concentration and albumin-creatinine ratio. In phase 2, all patients with an albumin concn greater than or equal to 15 mg/L and/or an albumin-creatinine ratio greater than or equal to 3.5 mg/mmol and a random sample of those with an albumin concn less than 15 mg/L and albumin-creatinine ratio less than 3.5 mg/mmol were asked to collect a timed overnight urine specimen for determination of AER. Among 1888 patients (16-60 yr old, diabetes onset less than 40 yr, and duration of diabetes less than 35 yr) who were screened, the prevalence of microalbuminuria was approximately 3.7% (95% confidence interval (CI) 2.7-7.6%). Duration of diabetes was significantly longer in micro- than normoalbuminuric patients (20 vs. 15 yr, respectively; P less than 0.001), and in no patient with microalbuminuria was the duration of diabetes less than 5 yr. Systolic and diastolic blood pressures, higher in micro- than normoalbuminuric patients (132 vs. 122 mmHg, P less than 0.01; 77 vs. 72 mmHg, P less than 0.01), were strongly associated with AER. Microalbuminuria in type I diabetes, which appears to represent an earlier phase in the development of clinical nephropathy, is associated with elevated blood pressure and a longer duration of diabetes.