Objectives: The aim of this study is to examine the effect of efficient management of RA on disability levels, in a large cohort of RA patients over a period of 3-years.
Methods: We studied 2,775 RA patients who had continuous enrollment for at least 3 years, among 7,511 RA patients enrolled in an observational cohort study, IORRA (Institute of Rheumatology Rheumatoid Arthritis), from October 2000 to April 2005. DAS28 scores were calculated at 6 months intervals for all the patients and a value less than 2.6 was considered as tight control. We have set up a new variable for each patient, “Avg-Dscore”, based on the transition of each patient’s DAS28 value, taking the threshold level of 2.6 into consideration. The “Avg-DAS28” is the average of DAS28 values over all the phases. Functional disability status was assessed by J-HAQ, the validated Japanese version of HAQ. The relationship of “Avg-Dscore” and “Avg-DAS28” with the functional disability level was determined using spearman correlation coefficients and multiple linear regression models.
Results: The baseline features of these 2,775 patients were: female 83.7%, mean age 56.8 years, mean RA duration 9.5 years, mean initial DAS28 4.0, mean initial J-HAQ score 0.79, and mean final J-HAQ score 0.86. There was a statistically significant correlation between “Avg-DAS28” and final J-HAQ score (r=0.57, p<0.0001), indicating that tighter disease control has significant association with lower disability levels. A similar relationship was observed between “Avg-Dscore” and final J-HAQ score (r= 0.47, p<0.0001). Multiple linear regression analysis, after adjusting for all the covariates, revealed that both “Avg-Dscore” and “Avg-DAS28” were the most significant factors contributing to final J-HAQ score, and confirmed the strong relationship between disease activity and functional disability.
Conclusions: In RA-patients efficient disease management, by maintaining the DAS28 values under 2.6, has significant association with improving functional capability. The threshold DAS28 level of 2.6 may be useful in developing guidelines of “treat to target” in RA patients.
- Disease Activity Score
- functional disability
- observational cohort study
- rheumatoid arthritis