title: Evaluation of plasma carboxy-terminal cross-linking telopeptide of type I collagen concentration in horses.
abstract: OBJECTIVE
  To evaluate a human assay for quantification of carboxy-terminal cross-linking telopeptide of type I collagen (CTX-I), assess the influence of age on plasma CTX-I concentration, investigate the relationship between plasma CTX-I and serum osteocalcin concentrations, and determine whether concentrations of plasma CTX-I or serum osteocalcin fluctuate in circadian manner in horses. HORSES: 75 clinically normal horses.
  
  
  METHODS
  Cross-reactivity between equine serum CTX-I and CTX-I antibodies in an automated electrochemiluminescent sandwich antibody assay (ECLIA) was evaluated via a specificity test (ie, dilution test) and recovery calculation. Serum osteocalcin concentration was measured with an equine-specific osteocalcin radioimmunoassay. To analyze diurnal variations in plasma CTX-I and serum osteocalcin concentrations, blood samples were obtained hourly during a 24-hour period.
  
  
  RESULTS
  Results of the dilution test indicated good correlation (r > 0.99) between expected serum CTX-I concentrations and measured serum CTX-I concentrations. The calculated CTX-I recovery was 97.6% to 109.9%. Plasma CTX-I and serum osteocalcin concentrations were correlated. Plasma CTX-I concentration was inversely correlated with age of the horse. No significant circadian variations in plasma CTX-I and serum osteocalcin concentrations were detected.
  
  
  CONCLUSIONS
  Results suggest that the fully automated CTX-I ECLIA can be used for evaluation of plasma and serum samples from horses and may be a useful tool to monitor bone metabolism changes. Horses in this study did not have notable diurnal fluctuations in serum osteocalcin and plasma CTX-I concentrations.
authors.affiliation: Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, University of Liège, Sart Tilman, Belgium.
authors.forename: Bianca
authors.initials: B
authors.lastname: Carstanjen
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Hoyle
authors.forename: Annick
authors.initials: A
authors.lastname: Gabriel
authors.forename: Olaf
authors.initials: O
authors.lastname: Hars
authors.forename: Charlotte
authors.initials: C
authors.lastname: Sandersen
authors.forename: Hélène
authors.initials: H
authors.lastname: Amory
authors.forename: Benoit
authors.initials: B
authors.lastname: Remy
mesh_terms: D000367:Age Factors; D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D003094:Collagen / Q000097:blood*; D024042:Collagen Type I; D006736:Horses / Q000097:blood* / Q000502:physiology; D007163:Immunosorbent Techniques; D008163:Luminescent Measurements; D015675:Osteocalcin / Q000097:blood*; D010455:Peptides / Q000097:blood*; D011863:Radioimmunoassay
chemical_list: D024042:Collagen Type I; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D015675:Osteocalcin; D003094:Collagen