title: Reference intervals for 24 laboratory parameters determined in 24-hour urine collections.
abstract: BACKGROUND
  Reference intervals for many laboratory parameters determined in 24-h urine collections are either not publicly available or based on small numbers, not sex specific or not from a representative sample.
  
  
  METHODS
  Osmolality and concentrations or enzymatic activities of sodium, potassium, chloride, glucose, creatinine, citrate, cortisol, pancreatic α-amylase, total protein, albumin, transferrin, immunoglobulin G, α1-microglobulin, α2-macroglobulin, as well as porphyrins and their precursors (δ-aminolevulinic acid and porphobilinogen) were determined in 241 24-h urine samples of a population-based cohort of asymptomatic adults (121 men and 120 women). For 16 of these 24 parameters creatinine-normalized ratios were calculated based on 24-h urine creatinine. The reference intervals for these parameters were calculated according to the CLSI C28-A3 statistical guidelines.
  
  
  RESULTS
  By contrast to most published reference intervals, which do not stratify for sex, reference intervals of 12 of 24 laboratory parameters in 24-h urine collections and of eight of 16 parameters as creatinine-normalized ratios differed significantly between men and women. For six parameters calculated as 24-h urine excretion and four parameters calculated as creatinine-normalized ratios no reference intervals had been published before. For some parameters we found significant and relevant deviations from previously reported reference intervals, most notably for 24-h urine cortisol in women. Ten 24-h urine parameters showed weak or moderate sex-specific correlations with age.
  
  
  CONCLUSIONS
  By applying up-to-date analytical methods and clinical chemistry analyzers to 24-h urine collections from a large population-based cohort we provide as yet the most comprehensive set of sex-specific reference intervals calculated according to CLSI guidelines for parameters determined in 24-h urine collections.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Curcio
authors.forename: Helen
authors.initials: H
authors.lastname: Stettler
authors.forename: Paolo M
authors.initials: PM
authors.lastname: Suter
authors.forename: Jasmin Barman
authors.initials: JB
authors.lastname: Aksözen
authors.forename: Lanja
authors.initials: L
authors.lastname: Saleh
authors.forename: Katharina
authors.initials: K
authors.lastname: Spanaus
authors.forename: Murielle
authors.initials: M
authors.lastname: Bochud
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Minder
authors.forename: Arnold
authors.initials: A
authors.lastname: von Eckardstein
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002624:Chemistry, Clinical; D003404:Creatinine / Q000652:urine*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D013997:Time Factors; D059349:Urine Specimen Collection; D055815:Young Adult
chemical_list: D003404:Creatinine