title: A comparison of methods for measuring serum and urinary markers of bone metabolism in cats.
abstract: Biochemical markers of bone cell activity have recently been shown to be useful for monitoring skeletal health in domestic animals, including dogs and horses. The aim of this study was to evaluate a number of biochemical assays, originally developed for use in humans, for their ability to measure indicators of bone cell activity in serum and urine of normal cats over a range of ages. Bone alkaline phosphatase (BAP), a marker of bone formation, was measured in serum using wheatgerm lectin precipitation (WGL) and by ELISA. The curve derived from serial dilution of feline serum was parallel with the ELISA standard curve, indicating species cross-reactivity, and there was a significant relationship between assays (rs = 0.97, P < 0.001). Deoxypyridinoline (DPD), a marker of bone resorption, was measured in its total form in urine by HPLC and ELISA, and in its free form in serum and urine by ELISA. The dilution curve for free DPD in urine showed parallelism with the assay standard curve; however, the curves for total DPD in urine and serum did not. A significant relationship was established between total urinary DPD (HPLC) with total serum DPD (rs = 0.69, P < 0.001), and with free urinary DPD (rs = 0.95, P < 0.001) concentrations. Carboxy-terminal telopeptide of type I collagen (CTX) concentration, another marker of bone resorption, was measured in serum and urine by ELISA, and there was a significant relationship between assays (rs = 0.82, P < 0.001). CTX could not be measured reliably using an auto-analysis method. A significant relationship was established between total urinary DPD (HPLC) with serum CTX (rs = 0.59, P < 0.05), and urinary CTX (rs = 0.65, P < 0.001) concentrations. BAP (ELISA and WGL), total urinary DPD (HPLC), urinary CTX (ELISA), and serum CTX (ELISA) concentrations were significantly inversely correlated with age (rs = -0.66, -0.88, -0.61, -0.70, and -0.51, P < 0.05 respectively). Cats under two years of age had significantly higher BAP, total urinary DPD (HPLC), and urinary CTX concentrations compared to older cats. In conclusion, this study has shown that a number of commercially available assays provide reliable methods for non-invasively monitoring bone cell activity in cats and has shown that bone turnover decreases within the first two years of life, until complete skeletal maturity is attained. Future studies can now be directed at evaluating the potential clinical application of these methods.
authors.affiliation: Bone and Mineral Centre, Department of Medicine, University College London, London WC1E 6JJ, UK. adelaur@nimr.mrc.ac.uk
authors.forename: A
authors.initials: A
authors.lastname: DeLaurier
authors.forename: B
authors.initials: B
authors.lastname: Jackson
authors.forename: D
authors.initials: D
authors.lastname: Pfeiffer
authors.forename: K
authors.initials: K
authors.lastname: Ingham
authors.forename: M A
authors.initials: MA
authors.lastname: Horton
authors.forename: J S
authors.initials: JS
authors.lastname: Price
mesh_terms: D000410:Alanine Transaminase / Q000652:urine; D000469:Alkaline Phosphatase / Q000097:blood / Q000652:urine; D000596:Amino Acids / Q000097:blood / Q000652:urine; D000818:Animals; D015415:Biomarkers / Q000032:analysis* / Q000097:blood / Q000652:urine; D001862:Bone Resorption / Q000097:blood / Q000652:urine / Q000662:veterinary; D001842:Bone and Bones / Q000378:metabolism*; D002415:Cats / Q000097:blood* / Q000652:urine*; D002851:Chromatography, High Pressure Liquid / Q000662:veterinary; D003094:Collagen / Q000097:blood / Q000652:urine; D024042:Collagen Type I; D003404:Creatinine / Q000652:urine; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005260:Female; D008297:Male; D010012:Osteogenesis; D010455:Peptides / Q000097:blood / Q000652:urine; D014508:Urea / Q000032:analysis; D005723:gamma-Glutamyltransferase / Q000652:urine
chemical_list: D000596:Amino Acids; D015415:Biomarkers; D024042:Collagen Type I; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D014508:Urea; C036020:deoxypyridinoline; D003094:Collagen; D003404:Creatinine; D005723:gamma-Glutamyltransferase; D000410:Alanine Transaminase; D000469:Alkaline Phosphatase