INCREASED LEVELS OF URINARY COLLAGEN CROSS-LINKS IN FEMALES WITH RHEUMATOID-ARTHRITIS

Bone loss is a feature of RA, but the exact mechanisms involved are no t clear. The collagen crosslinks deoxypyridinoline (DPYR) and pyridino line (PYR) are specific indices of 'mature' collagen breakdown and ref lect increased bone turnover. The aims of the study were to examine cr osslink levels in RA and their association with disease activity and t he effect of steroids. Urinary crosslinks corrected for creatinine wer e measured on morning fasting samples by HPLC in 70 postmenopausal wom en with rheumatoid arthritis (RA) aged 45-65 and compared with 169 pos tmenopausal healthy age-matched controls from the population. Mean lev els of PYR were significantly higher in RA cases than in controls (52. 4 versus 37.5 nmols/mmolCr) although mean levels of DPYR did not diffe r significantly. A weak correlation was found with ESR and PYR (r = 0. 35) but not with other markers of disease activity. Thirteen of the RA cases were current steroid users and their levels of DPYR and PYR eve n with low doses, were significantly elevated above those of non-users , ex-users and controls. The finding of raised urinary PYR but not the bone specific DPYR in nonsteroid using RA cases suggests that the inc reased collagen breakdown does not primarily come from bone but from o ther sources such as cartilage and synovium. The large increases in co llagen excretion in low dose steroid users, may reflect the higher ris k of osteoporosis in this group.