To examine the association of treatment response and disease duration with changes in rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibody levels among patients with rheumatoid arthritis (RA).
The study sample included 66 RA patients who completed double-blind, randomized clinical protocols and for whom baseline and followup serum samples were available. Anti-CCP and RF levels were measured using commercially available assay kits. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were used to describe the association of response and disease duration with declines in antibody levels.
Patients had a mean +/- SD age of 49.9 +/- 12.0 years and were predominantly female (n = 51; 77%). The mean +/- SD duration between the times at which the baseline and followup serum samples were obtained was 13.7 +/- 8.6 months. Among the 64 subjects with positive antibody at baseline, 33 (52%) experienced a > or =25% reduction in the anti-CCP antibody level during the course of treatment, and 35 patients (55%) had a > or =25% reduction in RF. After adjustment for the baseline anti-CCP antibody level, only a shorter disease duration (< or =12 months) was significantly associated with a decline in the level of anti-CCP antibody (OR 3.0, 95% CI 1.0-8.8), and no association with treatment response was observed. Conversely, treatment response was the only significant determinant of a decrease in RF levels (OR 3.6, 95% CI 1.2-10.4).
Shorter disease duration predicts greater declines in anti-CCP antibody levels with treatment in RA. Although treatment response is a robust determinant of a decrease in RF, it does not appear to be associated with declines in the anti-CCP antibody level.