title: Assessment and recommendations on factors contributing to preanalytical variability of urinary pyridinoline and deoxypyridinoline.
abstract: BACKGROUND
  Pyridinoline (PYD) and deoxypyridinoline (DPD) are two of the most extensively characterized biochemical bone markers, but the interpretation of results is hampered by biologic and other preanalytical variability. We reviewed factors contributing to preanalytical variation of pyridinium cross-links in urine.
  
  
  METHODS
  We searched four databases for English-language reports on PYD and/or DPD in urine. Searches were restricted to humans, except for studies of stability, when the search was expanded to other species. The 599 identified articles were supplemented with references from those articles and with articles known to the authors.
  
  
  RESULTS
  The mean reported within-day variability was 71% for PYD (range, 57-78%) and 67% for DPD (range, 53-75%). The mean interday variability was 16% for both DPD and PYD (range for PYD, 12-21%; range for DPD, 5-24%). The mean intersubject variabilities across studies were 26% for PYD (range, 12-63%) and 34% for DPD (range, 8-98%) for healthy premenopausal women and 36% (range, 22-61%) and 40%, (range, 27-54%) for postmenopausal women, respectively. Specimen instability and errors in creatinine measurements were additional sources of variability.
  
  
  CONCLUSIONS
  Intra- and intersubject variability can be reduced by collecting specimens at a specific time of the day and by maintaining similar patient status at each specimen collection regarding factors such as medications and dietary supplements.
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA 30341-3724, USA. hav2@cdc.gov
authors.forename: Hubert W
authors.initials: HW
authors.lastname: Vesper
authors.forename: Laurence M
authors.initials: LM
authors.lastname: Demers
authors.forename: Richard
authors.initials: R
authors.lastname: Eastell
authors.forename: Patrick
authors.initials: P
authors.lastname: Garnero
authors.forename: Michael
authors.initials: M
authors.lastname: Kleerekoper
authors.forename: Simon P
authors.initials: SP
authors.lastname: Robins
authors.forename: Apurva K
authors.initials: AK
authors.lastname: Srivastava
authors.forename: G Russell
authors.initials: GR
authors.lastname: Warnick
authors.forename: Nelson B
authors.initials: NB
authors.lastname: Watts
authors.forename: Gary L
authors.initials: GL
authors.lastname: Myers
mesh_terms: D000596:Amino Acids / Q000652:urine*; D001800:Blood Specimen Collection; D002940:Circadian Rhythm; D004032:Diet; D004347:Drug Interactions; D015444:Exercise; D005260:Female; D006801:Humans; D007774:Lactation / Q000652:urine; D008597:Menstrual Cycle; D011247:Pregnancy; D012621:Seasons
chemical_list: D000596:Amino Acids; C015484:pyridinoline; C036020:deoxypyridinoline