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Evaluation of plasma carboxy-terminal cross-linking telopeptide of type I collagen concentration in horses

Bianca Carstanjen Dr med vet, DEA1,2, Nicholas R. Hoyle PhD3, Annick Gabriel DVM, PhD4, Olaf Hars Dr rer nat5, Charlotte Sandersen DVM, DEA6, Hélène Amory DVM, PhD7, and Benoit Remy DVM8
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  • 1 Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, University of Liège, Sart Tilman, Liège, Belgium.
  • | 2 Present address is the Département d'Elevage et de Pathologie des Equidés, Ecole Nationale Vétérinaire d'Alfort, 7, Av. Général de Gaulle, 94704 Maisons-Alfort Cedex, France.
  • | 3 Section of Bone Metabolism & Anemia, Roche Diagnostics GmbH, Penzberg, Germany.
  • | 4 Department of Morphology and Pathology, Faculty of Veterinary Medicine, University of Liège, Sart Tilman, Liège, Belgium.
  • | 5 Research Institute Havelhöhe, Berlin, Germany.
  • | 6 Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, University of Liège, Sart Tilman, Liège, Belgium.
  • | 7 Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, University of Liège, Sart Tilman, Liège, Belgium.
  • | 8 Department of Physiology of Reproduction, Faculty of Veterinary Medicine, University of Liège, Sart Tilman, Liège, Belgium.

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.

Procedure—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 and Clinical Relevance—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. ( Am J Vet Res 2004;65:104–109)

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.

Procedure—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 and Clinical Relevance—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. ( Am J Vet Res 2004;65:104–109)