Objective: To analyze the clinical significance of serial measurements of serum matrix metalloproteinase 3 (MMP-3) levels in relation to markers of disease activity and radiological progression in early rheumatoid arthritis (RA).
Methods: In a 3 year prospective study of 33 patients with early RA (symptoms < 1 year at entry) monthly measurements of serum MMP-3 were transformed into time integrated values for 6 month periods for comparison with other markers of disease activity like swollen joint count (SJC), tender joint count (TJC), Ritchie articular index (RAI), the disease activity score (DAS), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and radiological progression, scored according to Sharp's method, in which erosions and joint space narrowing are scored separately and combined to a total Sharp score.
Results: Significant correlations were found between serum MMP-3 and SJC, ESR, and CRP during all periods and between 6 and 30 months with the DAS. There were no correlations between serum MMP-3 and TJC or the RAI. During the first 12 months serum MMP-3 was correlated only with the item joint space narrowing of the Sharp score. After 12 months of followup it was also correlated with the total Sharp score and after 18 months it was correlated with all 3 items of the Sharp score. There was a wide interindividual variation in the relation between serum MMP-3 and radiological progression but intraindividually this relation seemed to be rather constant.
Conclusion: Time integrated values of serum MMP-3 are correlated with time integrated values of other markers of disease activity such as joint swelling, ESR, CRP, and the DAS. Of the radiological scores, as outcome measures, especially joint space narrowing correlated closely with cumulative serum MMP-3.