Quantitation of microalbuminuria using random urine samples

Abstract 

Microalbuminuria is a harbinger of progressive renal disease and cardiovascular complications in patients with diabetes mellitus. The method most commonly used to measure microalbuminuria relies on a timed urine collection, either a 24-h or overnight specimen, which is time-consuming, cumbersome, and often inaccurate. We compared microalbumin-creatinine ratio (U_MA/U_Cr) in a random urine sample obtained after the first voided morning specimen with the quantity of microalbumin in a 24-h collection to determine whether the U_MA/U_Cr correlates with the microalbumin content of 24-h urine collection. In a study of 124 urine samples from 97 pediatric patients with type I diabetes, daily microalbumin excretion varied from 7 to 108 mg/24-h with a mean of 55.7±18.2 mg and U_MA/U_Cr ranged from 5 to 59 µg/mg with a mean of 39.4±11.3. An excellent correlation was found between the microalbumin excretion measured in 24-h urine collections and the random urine U_MA/U_Cr specimens (r=0.89, P<0.001). All patients who excreted more than 30 mg microalbumin in the 24-h specimen also had a U_MA/U_Cr of more than 20 µg/mg in the randomly voided sample. Microalbuminuria was unlikely if the U_MA/U_Cr was below 20 µg/mg. The results of this study indicate that the measurement of U_MA/U_Cr in a second voided morning specimen is a simple and reliable method for monitoring microalbuminuria in diabetic patients and may replace the need to assess quantitative microalbumin excretion on 24-h urine collections.