Quantitation of Microalbuminuria Using Random Urine Samples

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 microg/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 microg/mg in the randomly voided sample. Microalbuminuria was unlikely if the U(MA)/U(Cr) was below 20 microg/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.