Evaluation of free and peptide bound collagen crosslink excretion in different skeletal diseases.

OBJECTIVE To investigate urinary fractions of free and peptide forms of collagen crosslinks in patients with rheumatoid arthritis (n=50), osteoarthrosis (n=38), psoriatic arthritis (n=38) and in healthy volunteers (33 adults, 17 children). METHODS Pyridinoline (PYD) and deoxypyridinoline (DPD) were measured by high performance liquid chromatography. RESULTS In rheumatoid arthritis (RA) all fractions of PYD and DPD were significantly raised compared with osteoarthritis, psoriatic arthritis, and healthy controls. PYD and DPD correlated with disease activity in RA. In RA the collagen degradation resulted in primarily peptide bound forms. CONCLUSION The correlation between total peptide bound or free collagen crosslinks in different chronic joint diseases varies; however, this variation does not allow for a reliable differentiation between inflammatory and degenerative joint diseases.