Excretion of pyridinium crosslinks correlates with disease activity and appendicular bone loss in early rheumatoid arthritis.

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Abstract
OBJECTIVE--To establish if urinary excretion rates of the collagen crosslinks pyridinoline and deoxypyridinoline, which are known to be elevated in established rheumatoid arthritis (RA), are useful markers of bone loss in this disease. METHODS--Eight hour urine collections on all patients and 52 controls were performed, and the rates of pyridinoline and deoxypyridinoline excretion were measured. Bone mineral density (BMD), by dual energy x-ray absorption, and full laboratory and clinical assessments were performed. RESULTS--The rates of excretion of pyridinoline and deoxypyridinoline were significantly increased in patients compared with controls (p < 0.001). Pyridinoline excretion was associated with increased disease activity (ESR/CRP) but not disability (HAQ score/Functional Grade), and correlated with BMD loss at the femoral neck (p < 0.01). CONCLUSION--The excretion of collagen crosslinks may be useful as markers of bone and cartilage turnover in patients with RA.