title: Basic or extended urine sampling to analyse urine production?
abstract: BACKGROUND
  Frequency volume charts are valuable tools to objectify urine production in patients with nocturia, enuresis or nocturnal incontinence. Analyses of daytime and nighttime urine (=basic collection) or analyses of urine samples collected every 3 h (=extended collection) extend this evaluation by describing circadian patterns of water and solute diuresis (=renal function profiles).
  
  
  OBJECTIVE
  To assess intra-individual correlation and agreement between renal function profiles provided using basic and extended urine collections, and using two extended urine collections. To create a short-form of the extended collection.
  
  
  METHODS
  This prospective observational study was executed at Ghent University Hospital, Belgium. Study participation was open for anyone visiting the hospital. Participants collected one basic and two extended 24-h urine collections. Urinary levels of osmolality, sodium and creatinine were determined.
  
  
  RESULTS
  There was a moderate to strong correlation between results of basic and extended urinalyses. Comparing both extended urinalyses showed a moderate correlation between the eight individual samples and a weak to strong correlation between the mean daytime and nighttime values of renal functions. Different samples could be considered as most representative for mean daytime values, while all samples collected between 03 and 05am showed the highest agreement with mean nighttime values of renal function.
  
  
  CONCLUSIONS
  Since there is a good correlation and agreement between basic and extended urine collections to study the mechanisms underlying urine production, the choice of urine sampling method to evaluate urine production depends on the purpose. A nighttime-only urine sample collected between 03 and 05am may be the most practical approach.
authors.affiliation: Department of Urology, Ghent University Hospital, Ghent, Belgium.
authors.forename: Marie-Astrid
authors.initials: MA
authors.lastname: Denys
authors.affiliation: Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium.
authors.forename: Vansh
authors.initials: V
authors.lastname: Kapila
authors.affiliation: Department of Urology, SUNY Downstate Medical Center, New York City, New York.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Weiss
authors.affiliation: Department of Urology, Ghent University Hospital, Ghent, Belgium.
authors.forename: An-Sofie
authors.initials: AS
authors.lastname: Goessaert
authors.affiliation: Department of Urology, Ghent University Hospital, Ghent, Belgium.
authors.forename: Karel
authors.initials: K
authors.lastname: Everaert
mesh_terms: D000328:Adult; D001530:Belgium; D002940:Circadian Rhythm; D003404:Creatinine / Q000652:urine; D004231:Diuresis; D004775:Enuresis / Q000652:urine; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D053158:Nocturia / Q000652:urine*; D053206:Nocturnal Enuresis / Q000652:urine*; D009994:Osmolar Concentration; D011141:Polyuria / Q000652:urine*; D011446:Prospective Studies; D012964:Sodium / Q000652:urine; D016482:Urinalysis / Q000379:methods*; D014549:Urinary Incontinence / Q000652:urine; D059349:Urine Specimen Collection / Q000379:methods*
chemical_list: D012964:Sodium; D003404:Creatinine
keywords: diagnosis; diuresis; nocturia; nocturnal polyuria; physiopathology