The diagnostic utility of matrix metalloproteinase-3 and high-sensitivity C-reactive protein for predicting rheumatoid arthritis in anti-cyclic citrullinated peptide antibody-negative patients with recent-onset undifferentiated arthritis.

Anti-cyclic citrullinated peptide (anti-CCP) antibodies are well-established serological markers that show high sensitivity and specificity in early rheumatoid arthritis (RA) and are associated with bone erosions of RA. However, some patients subsequently progress to RA even if there is no presence of anti-CCP antibodies in an early stage. The aim of this study is to evaluate the diagnostic utility of matrix metalloproteinase-3 (MMP-3), high-sensitivity C-reactive protein (hsCRP) and IgM rheumatoid factor for predicting RA in anti-CCP-negative patients with recent-onset undifferentiated arthritis (UA). Baseline levels of those markers were measured at the entry of the study. A total of 99 patients with UA were included, among them 44 patients (44.4 %) had been classified as having RA by a skilled rheumatologist at some point during 1-year follow-up. Of these 99 patients, 34 patients (34.3 %) had anti-CCP antibodies and 65 patients (65.7 %) had no anti-CCP antibodies. Eleven patients who were anti-CCP-negative developed RA. We compared sensitivity, specificity, positive predictive value and negative predictive value of serum markers of these anti-CCP-negative RA patients. The combined usage of MMP-3 with hsCRP is relatively superior to other markers as predictors of RA.