Background: To determine the intraindividual coefficient of variation (CV(i)) of albumin excretion rate (AER).
Method: We studied 76 patients with type 1diabetes and 66 non-diabetic subjects (ND) under routine clinical conditions providing three timed overnight urine samples for urinary albumin determination by radioimmunoassay.
Results: Patients and ND had similar CV(i) of AER (50.7+/-33.3 vs. 58.1+/-33.2% P=0.12). Intermittent microalbuminuric subjects (one out of 3 AER >20 microg/min) had higher CV(i) of AER than normoalbuminuric and persistent microalbuminuric patients, [84.9 (37.1-145. 3) vs. 39.8 (4.9-124.8) vs. 34.6 (12.1-116.5)% P=0.0007] without difference between the two latter groups. In patients, the independent factor associated with the CV(i) of AER in multiple regression analysis was age (r(2)=0.08; P=0.01). Sensitivity (95% CL) and specificity of first AER for diagnosing microalbuminuria was 85.7% (42.0-99.2) and 91.3% (81.4-96.4). CONCLUIONS: Our findings suggest the variability of AER was physiological, unrelated to diabetic condition. First AER could be used for screening of microalbuminuria followed by a second one when the patient has AER >20 microg/min in the first. This would result in low cost for screening and diagnosis of microalbuminuria, that is not always feasible in routine clinical practice in developing countries using three urine samples.