Aim: Serum levels of C-reactive protein (CRP) and matrix metalloproteinase-3 (MMP-3) are used as indicators of the activity of rheumatoid arthritis (RA). The aim of this study was to characterize the clinical features of patients showing exclusive elevation of either serum CRP or MMP-3, and the differences in the time-course of changes between the serum levels of MMP-3 and CRP after initiation of therapy. Methods: A total of 129 RA patients were classified into four groups according to the serum levels of CRP and MMP-3 at the time of enrolment: Negative for both CRP and MMP-3 levels; positive for both; positive for CRP alone (CRP-positive group); and positive for MMP-3 alone (MMP-3-positive group). The analysis included evaluation of the serum CRP and MMP-3 levels, and the Lansbury Articular Index at enrolment and at final observation. Results: In the CRP-positive group (19%), 21% of the patients remained CRP-positive at the final observation; 42% became double-negative, and 31% became double-positive. In contrast, in the MMP-3-positive group (9%), about two-thirds of the patients remained MMP-3-positive at the final observation. The disease duration in the MMP-3-positive group was significantly longer, and the ratio of the number of large swollen joints to the total number of swollen joints was higher as compared with that in the other groups. Furthermore, elevated serum CRP responded faster to disease-modifying antirheumatic drug therapy than elevated serum MMP-3. Conclusions: Serum CRP is a better predictor of the response to treatment than serum MMP-3, which is associated to a greater extent with large joint involvement.
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