Connective tissue metabolism in patients with unclassified polyarthritis and early rheumatoid arthritis. Relationship to disease activity, bone mineral density, and radiographic outcome.

OBJECTIVE: To assess the applicability of serum concentrations of markers of synovial inflammation, cartilage, and bone metabolism in relation to conventional markers of disease activity, bone mineral density (BMD) of the hand, and radiographic outcome.
METHODS: Biochemical markers of collagen tissue metabolism were measured in 72 patients with symmetrically swollen and tender second and third metacarpophalangeal or proximal interphalangeal joints for at least 4 weeks and less than 2 years. At 2 years, 51 patients fulfilled the American College Rheumatology criteria for rheumatoid arthritis (RA) and 21 patients had unclassified polyarthritis. Patients with RA were divided into groups according to the mean disease activity and to magnetic resonance imaging and radiographically detected bone erosions in the hands.
RESULTS: Patients with RA had significantly higher serum concentrations of matrix metalloproteinase-3 (MMP-3) at baseline and higher mean concentrations of serum MMP-3 and pyridinoline (Pyd) during the first 6 and 12 months than patients with unclassified polyarthritis. RA patients with persistent disease activity and erosive disease had significantly higher concentrations of serum MMP-3 and Pyd than patients with no disease activity or nonerosive disease. Significant mutual correlations between serum MMP-3 and Pyd and C-reactive protein and erythrocyte sedimentation rate were observed. The mean values of MMP-3 and Pyd correlated significantly to the alpha coefficient of the digital x-ray radiogrammetry (DXR-BMD).
CONCLUSION: Serum MMP-3 and Pyd varied according to disease activity, periarticular osteoporosis measured by DXR, and radiographic outcome, and thus appear to supplement the conventional markers of disease activity for monitoring patients with RA.