Treating Rheumatoid Arthritis To Target: Is Low Disease Activity Good Enough?

Background/Purpose:  It is now widely recognised that treat-to-target (T2T) principles in rheumatoid arthritis (RA) are effective in achieving optimal disease outcomes. The aim of this study was to examine for differences in outcomes between low (LDAS) and remission (RDAS) disease activity score (DAS) categories, to establish whether LDAS is an acceptable treatment target in RA.
Methods: Data from two consecutive, similarly designed UK multi-centre RA inception cohorts, were used: the Early RA Study (ERAS) and Early RA Network (ERAN). Recruitment figures/median follow up for ERAS and ERAN were 1465/10 years (maximum 25 years), and 1236/6 years (maximum 10 years) respectively. Standard demographic and clinical variables were recorded at baseline and then annually until the end of study follow up. Disease activity was categorised by mean DAS28 score between years 1-5 as remission [mRDAS<2.6] or low [mLDAS 2.6-3.2]; as sustained low/remission DAS (sLDAS/sRDAS) based on DAS persisting in each of the two categories at years 1-2 and as Boolean remission (years 1-2). Change in HAQ and SF36 (physical [PCS] and mental [MCS] components) for each disease activity category were modelled using linear mixed models with time incorporated as a linear spline with change-point at 12 months. Year of onset, age, gender and use of steroids or conventional DMARDS at first visit were included as covariates.
Results: Out of 2701 patients, 468 (17%) were in mRDAS, 284 (11%) in mLDAS in the first five years of disease. Lower proportions had achieved sRDAS (8%), sLDAS (6%) and Boolean (2%) remission (table). Mean age was similar across categories; more women were in low vs remission DAS. Compared to mLDAS or sLDAS, inflammatory markers, DAS, functional (HAQ, PCS) and mental (MCS) scores tended to be better in the mRDAs, sRDAS or Boolean remission categories. Significant differences (p<0.05) were noted between the mRDAS and mLDAS between years 1-5 for all outcomes; for sRDAS compared to sLDAS, the difference was significant at one year but not by five years (figure).

Conclusion: This study demonstrates striking differences between remission and low DAS categories, suggesting worse functional and SF36 outcomes over time in the low DAS categories. The findings support that remission should be the primary T2T goal in in RA.

Figure. Disease outcomes by DAS category.