First-Morning Versus Spot Urine to Assess Microalbuminuria

A first-morning void provides a more reliable measurement of urinary albumin excretion (UAE) than does a spot urine sample, according to a paper from the Journal of the American Society of Nephrology.

Researchers compared the findings of 24-hour urine collections, first-morning voids, and spot urine samples in 241 men and women. The UAE was measured in the 24-hour collections, while urinary albumin concentration (UAC) and albumin:creatine ratio (ACR) were measured in the morning and spot samples.

Based on UAE measurement in 24-hour urine collections, the prevalence of microalbuminuria was 10 percent. This was similar to the 7.5 percent rate in first-morning void specimens, both on UAC and ACR. In contrast, tests in spot urine samples overestimated the prevalence of microalbuminuria: 25.4 percent for UAC and 22.4 percent for ACR [Witte EC, Heerspink HJL, de Zeeuw D, Bakker SJL, de Jong PE, and Gansevoort R: First morning voids are more reliable than spot urine samples to assess microalbuminuria. J Am Soc Nephrol 2009; 20:436–443].