title: Reference intervals of bone turnover markers determined by using their curve-fitting valley for adult females in China.
abstract: CONCLUSIONS
  The reference values for bone turnover markers (BTMs) have a significant role in the diagnosis, monitoring, and treatment of metabolic bone disease. This study proposes that the peak value of bone mineral density and the trough value for the BTM curve can be used to determine the reference range of BTM.
  
  
  BACKGROUND
  The aim of this study is to determine the reference intervals of BTMs for adult females in China with an attempt to reference the peak bone mineral density (BMD) with the corresponding BTM valley.
  
  
  METHODS
  This study included 546 premenopausal and 394 postmenopausal women. The levels of several BTMs were determined, and the BMD was measured using a dual-energy X-ray absorptiometry.
  
  
  RESULTS
  The BTMs of postmenopausal women were 17-96 % higher than premenopausal women. The change of BTM with age presented an optimal goodness-of-fit according to the cubic regression model (R (2) = 0.074-0.346, all P = 0.000). All kinds of BTM levels were positively correlated with age in premenopausal women aged 27-56 years old (r = 0.167-0.502, P = 0.023-0.000). Except for uCTX, the BTM reference value determined using a curve-fitting valley was significantly lower than the reference values for premenopausal women. The BTM reference values determined in this study were also significantly different from the reference values given by the manufacturers of the reagents used.
  
  
  CONCLUSIONS
  This study found that the changes of level with age of BTMs in Chinese women present an optimal goodness-of-fit according to the cubic regression model. The fitting valley corresponds to the BMD fitting peak and may possibly be an effective means of determining the BTM reference intervals.
authors.affiliation: Institute of Metabolism and Endocrinology, The Second Xiangya Hospital, Central South University, No.139 Middle Renmin Road, Changsha, Hunan, 410011, People's Republic of China.
authors.forename: X-Y
authors.initials: XY
authors.lastname: Wu
authors.forename: H
authors.initials: H
authors.lastname: Zhang
authors.forename: H
authors.initials: H
authors.lastname: Xie
authors.forename: X-H
authors.initials: XH
authors.lastname: Luo
authors.forename: Y-Q
authors.initials: YQ
authors.lastname: Peng
authors.forename: L-Q
authors.initials: LQ
authors.lastname: Yuan
authors.forename: R-C
authors.initials: RC
authors.lastname: Dai
authors.forename: Z-F
authors.initials: ZF
authors.lastname: Sheng
authors.forename: X-P
authors.initials: XP
authors.lastname: Wu
authors.forename: E-Y
authors.initials: EY
authors.lastname: Liao
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood / Q000502:physiology; D000886:Anthropometry; D044466:Asian People / Q000706:statistics & numerical data; D015415:Biomarkers / Q000097:blood*; D015519:Bone Density / Q000502:physiology*; D016723:Bone Remodeling / Q000502:physiology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D017698:Postmenopause / Q000097:blood / Q000502:physiology; D017697:Premenopause / Q000097:blood / Q000502:physiology; D012016:Reference Values; D055815:Young Adult
chemical_list: D015415:Biomarkers