Collagen type IIC-telopeptide fragments as an index of cartilage degradation

We report the development of an assay for measurement of the urinary concen tration of collagen type II C-telopeptide fragments. This assay was develop ed for providing a specific marker of joint metabolism. A monoclonal antibo dy, recognizing a linear six amino acid epitope from the middle region of t he collagen type II C-telopeptide was used in a competitive enzyme-linked i mmunoassay (ELISA) format for measurement of urine samples. The technical p erformance and specificity of the assay was evaluated and a panel of sample s from patients with rheumatoid arthritis (RA) (n = 27), osteoarthritis (OA ) (n = 29), Paget's disease (n = 9), and healthy controls (n = 428) was mea sured in the assay. The ELISA was specific for the peptide EKGPDP derived f rom collagen type II C-telopeptide: it did not recognize peptides from the N-telopeptide of the molecule or from other collagen types. Collagen type I I C-telopeptide fragments measured in the assay resisted seven freeze-thaw cycles and >20 h of storage at room temperature. RA and OA patients showed significant 2.33-fold (95% confidence interval [CI] 1.50-3.16) and 1.53-fol d (CI 1.24-1.82) elevations in CartiLaps concentration, respectively. Paget 's disease patients did not have elevated CartiLaps levels. RA patients wit h radiological evidence of cartilage damage had significantly higher (1.79- fold, CI 1.04-2.54) CartiLaps levels than RA patients without radiological evidence of cartilage destruction. The Cartilaps assay showed high technica l precision and an ability to differentiate populations with an elevated jo int metabolism from normal controls. This suggests that the assay may have clinical value in assisting in the diagnosis of joint diseases and in monit oring progression and therapy in RA and OA. (Bone 29:209-215; 2001) (C) 200 1 by Elsevier Science Inc. All rights reserved.