To estimate the prevalence of microalbuminuria, overnight urinary albumin excretion rate (AER) ≥30 and ≤250 μg/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 ≥15 mg/L and/or an albumin-creatinine ratio ≥3.5 mg/mmol and a random sample of those with an albumin concn <15 mg/L and albumin-creatinine ratio <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 <40 yr, and duration of diabetes <35 yr) who were screened, the prevalence of microalbuminuria was ∼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 <0.001), and in no patient with microalbuminuria was the duration of diabetes <5 yr. Systolic and diastolic blood pressures, higher in micro- than normoalbuminuric patients (132 vs. 122 mmHg, P <0.01; 77 vs. 72 mmHg, P <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.
