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First Morning Voids Are More Reliable Than Spot Urine Samples to Assess Microalbuminuria

2008; American Society of Nephrology; Volume: 20; Issue: 2 Linguagem: Inglês

10.1681/asn.2008030292

1533-3450

Elsbeth C. Witte, Hiddo J.L. Heerspink, Dick de Zeeuw, Stephan J. L. Bakker, Paul E. de Jong, Ronald T. Gansevoort,

Renal and Vascular Pathologies

Measurement of urinary albumin excretion (UAE) in a 24-h collection is the gold standard method to determine the presence of microalbuminuria. We sought to compare more practical alternatives—measurement of urinary albumin concentration (UAC) or albumin:creatinine ratio (ACR)—in a first morning void or in a spot urine sample with this gold standard. We asked 241 participants of a prospective cohort study to make three 24-h urine collections, a first morning void, and a spot urine sample. Regression analysis showed that the ACR in a first morning void best agreed with 24-h UAE. The prevalence of microalbuminuria determined by data from a first morning void (7.5%, whether by UAC or ACR) nearly equaled the prevalence of microalbuminuria determined by 24-h UAE (10.0%), whereas the prevalence was higher when determined by spot urine samples (25.4% for UAC and 22.4% for ACR; both P < 0.001 versus 24-h UAE). The intraindividual coefficients of variation of the ACR in a first morning void and 24-h UAE were similar (19%). Intraindividual coefficients of variations of all other measurements of albuminuria were significantly greater. In conclusion, measurement of albuminuria in a first morning void, preferably as the ACR, is more reliable than a spot urine sample to diagnose and monitor microalbuminuria.