title: First morning voids are more reliable than spot urine samples to assess microalbuminuria.
abstract: 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.
authors.affiliation: Department of Nephrology, University Medical Center Groningen, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
authors.forename: Elsbeth C
authors.initials: EC
authors.lastname: Witte
authors.forename: Hiddo J
authors.initials: HJ
authors.lastname: Lambers Heerspink
authors.forename: Dick
authors.initials: D
authors.lastname: de Zeeuw
authors.forename: Stephan J L
authors.initials: SJ
authors.lastname: Bakker
authors.forename: Paul E
authors.initials: PE
authors.lastname: de Jong
authors.forename: Ronald
authors.initials: R
authors.lastname: Gansevoort
mesh_terms: D000368:Aged; D000418:Albumins; D000419:Albuminuria / Q000175:diagnosis*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009398:Nephrology / Q000379:methods*; D012016:Reference Values; D012044:Regression Analysis; D015203:Reproducibility of Results; D012709:Serum Albumin; D013997:Time Factors; D016482:Urinalysis / Q000379:methods*
chemical_list: D000418:Albumins; D012709:Serum Albumin