Progression to rheumatoid arthritis in patients with undifferentiated arthritis with a positive anti-cyclic citrullinated peptides antibody and a negative C-reactive protein

Abstract

Objective: To evaluate the progression rate to rheumatoid arthritis (RA) in patients with undifferentiated arthritis (UA) with a positive anti-cyclic citrullinated peptides (CCP) antibody and a negative C-reactive protein (CRP).
Methods: We calculated the rate of progression to RA in 50 patients with UA with a positive anti-CCP antibody and a negative CRP from retrospective clinical data.
Results: Among the 50 UA patients, 22 patients (44%) progressed to RA by 1987 ACR criteria during 25.1±13.9months observation. Patients who progressed to RA had a significantly higher rheumatoid factor and a greater number of swollen joints on first visit and more were found to be CRP-positive, satisfy the criteria for early RA by JCR 1994, and satisfy the diagnostic criteria for RA by ACR/EULAR 2009than patients who had not progressed to RA.
Conclusion: Even if CRP is negative upon the first visit, the rate of development to RA in UA patients with a positive anti-CCP antibody and more swollen joints on first visit is high.