'Insights in the relationship of joint space narrowing versus erosive joint damage and physical functioning of patients with RA'.
OBJECTIVE
To evaluate the contribution of joint space narrowing (JSN) and erosions in general and in four different joint groups in relation to physical disability in rheumatoid arthritis (RA).


METHODS
5-year follow-up data from the Behandel Strategieën (BeSt) trial were used, where 508 patients with recent onset RA were treated aiming at a disease activity score≤2.4. Joint damage was assessed annually and scored according to the Sharp-van der Heijde method. Physical disability was measured 3-monthly with the Health Assessment Questionnaire (HAQ). Generalised Estimating Equations analyses were performed to assess the relationship between the HAQ and JSN scores and erosions scores, separately and in joint groups.


RESULTS
Overall, damage scores were low, and neither total JSN nor erosions showed a significant effect on HAQ (β=0.001 95% CI -0.003 to 0.004 and β=0.002 95% CI -0.001 to 0.006, respectively). Of the total damage scores per joint group, damage in the wrist shows a trend for association with physical disability displaying the largest effect size (β=0.005 95% CI 0.000 to 0.011). Also in the analysis with erosions per joint group, the wrist was most strongly related with physical functioning (β=0.016 95% CI 0.003 to 0.029); in the analysis with JSN per joint group no joint group was significantly related to the HAQ. Analysis of all erosion and narrowing scores per joint group in one model reveals only erosions in the wrist to be independently associated with impaired physical functioning (β=0.017 95% CI 0.003 to 0.030).


CONCLUSIONS
Joint damage in the wrist, erosions more than JSN, is associated with impaired physical functioning even in patients with early RA with limited overall damage after 5 years tightly controlled treatment.