Background In patients with rheumatoid arthritis (RA), joint damage can determine irreversible physical disability. The different types of joint structures affected can be evaluated separately on radiographs as erosions (E), joint space narrowing (JSN) or (sub)luxation (SLUX).
Objectives To evaluate longitudinally the separate effects of E (reflecting bone damage), JSN (cartilage loss) and SLUX (soft tissue damage) in four different joint groups (PIPs, MCPs, wrist, MTPs) on physical disability in patients with RA.
Methods 3-year follow-up data from the Rheumatoid Arthritis PreventIon of structural Damage 1 (RAPID1) trial were used (1). RAPID1 was a randomised controlled trial comparing 2 dosages of certolizumab (CZP) plus methotrexate (MTX) vs. MTX in patients with RA. Physical function was measured by the Health Assessment Questionnaire (HAQ) score at each visit. Radiographic damage was measured by the van der Heijde-modified Sharp score (SvdH) on radiographs of hands and feet obtained every 6 months in the first 2 years and at year 3. Separate scores for E, JSN and SLUX were available, allowing comparisons between all 3 components of the SvdH. Generalised Estimating Equations analyses were performed to assess the relationship between the HAQ and E, JSN and SLUX scores, separately and in all joint groups.
Results In separate models for each type of damage and after adjusting for age, gender, baseline disease activity and treatment group, E and JSN were more strongly associated with HAQ than SLUX (table 1). In combined models, JSN was the most important predictor of HAQ (β 0.003, 95% CI 0.002-0.005) when all joints were included together (table 2). When separate joint groups were analyzed, erosions in the wrist were the most important predictor of function (β 0.007, 95%CI 0.004-0.011).
Conclusions This study is demonstrating that among RA-related joint damage, as reflected by radiographic changes, cartilage loss quantified by JSN is the most important predictor of physical disability. However, when analyzing joint groups separately, erosions in the wrist are the most important predictor of function loss.
Keystone E et al. Arthritis Rheum. 2008 Nov;58(11):3319-29
Acknowledgements AMG was supported by a EULAR scientific training bursary for 6 months and by an educational grant from UCB.
Disclosure of Interest : None declared