Background Very few studies have previously assessed the separate effects of the different types of radiographic damage on disability in RA patients. Their results suggest that joint space narrowing (JSN) rather than erosions is the main driver of disability. Nevertheless, these studies did not distinguish (sub)luxation from true JSN or they applied HAQ-score as the sole outcome measure for disability.
Objectives To assess the independent relationship of true JSN, (sub)luxation, and erosions with disability in RA patients. Secondly, to investigate the influence of radiographic damage in different hand joint groups (PIP, MCP and wrist joints) on disability.
Methods Data from the EURIDISS cohort including RA patients with disease duration ≤4 years followed over 10 years were used. The relationship between the three types of radiographic damage and disability (grip strength, HAQ and dexterity scale in AIMS) was investigated. Data from 167 patients with hand radiographs in ≥2 visits were longitudinally analysed by GEE using separate models per type of damage and joint group as well as combined models (including all types of damage) adjusted for age, sex, Ritchie index, ESR and treatment.
Results Mean ± SD baseline values were 0.90±0.62 for HAQ-score and 15.6±7.6 kg for grip strength in females and 33.8±12.8 kg in males. Median (range) Sharp-van-der-Heijde score was 2 (0-61) and increased on average with 20 units after 10 years. All types of damage were inversely associated with grip strength in the analysis of separate models, but only “true JSN” had an independent and statistically significant contribution in the combined analysis (Table). Neither JSN, (sub)luxation nor erosions were associated with HAQ-score while erosions were associated with the AIMS dexterity scale only in the analysis of separate models. After stratifying for hand joint group, erosions at MCPs and true JSN at wrist were significantly related to grip strength. Erosions at PIPs and MCPs were the only type of damage associated with HAQ-score and AIMS dexterity, respectively.
Conclusions All types of radiographically visible joint damage may interfere with important but different aspects of physical functions. True JSN is most closely related to hand function.
Acknowledgements This study was supported by grants from the Eastern Norway Regional Health Authority. The data collection in EURIDISS was supported by The Research Council of Norway, The Norwegian Rheumatism Association, The Norwegian Women Public Health Association, The Norwegian ExtraFoundation for Health and Rehabilitation, the Grethe Harbitz Legacy and the Marie and Else Mustad's Legacy. VNC was partially supported by a grant from the Fundaciόn Española de Reumatología.
Disclosure of Interest None declared