Decreasing the variability observed in urine analysis.

Urine analysis is affected significantly by biological variability. The objective of this study was to study the feasibility of reducing the biological variability of excretion of various analytes in urine, especially albumin in children with diabetes, by mixing small volumes of early morning samples. Twenty-two male children with type 1 diabetes collected early morning aliquots of approximately 10 ml of urine on 3 consecutive days and kept them refrigerated in sealed containers. The urine collection was repeated every 4-6 months in the diabetic children. Ten normal children and 10 normal adults participated as controls. The specimens were analyzed individually and as mixed samples for each subject. Mixing the 3 urine samples before analysis decreased the biological variability of all urine assays (albumin, glucose, creatinine, total protein, potassium). The diabetic children had 3 times higher variability of urine albumin (as a ratio to creatinine) compared to normal children, when the urine samples were collected individually (61% vs 19%, respectively). The variability in the diabetic children decreased when the 3 specimens were analyzed as a single sample after mixing, especially when urine albumin was expressed as a ratio to creatinine. Blood glycated hemoglobin levels correlated better with urine glucose levels when 3 urine samples were mixed before analysis.