Background/Purpose: Previous cross-sectional data revealed disease activity (DA) measures that omit foot joint assessment inadequately capture foot synovitis in in apparent remission at 6 months¹. We sought to determine whether foot synovitis is associated with adverse radiographic and functional outcomes after 3 years in an inception cohort receiving treat-to-target combination DMARD therapy. 

Methods: Patients with early RA (<1 year; fulfilling ACR 1987 and/or 2010 classification criteria) were included. Remission was assessed using DAS28, clinical disease activity index (CDAI) and simplified disease activity index (SDAI); radiographic outcomes by annual hand and feet radiographs scored by the van der Heijde modified Sharp score and quality of life by SF-36. The prevalence of remission by different DA criteria and presence of foot synovitis was estimated using marginal binomial generalised estimating equations and transition between disease remission and non-remission states using a multi-state Markov model. Changes in radiographic scores were analysed using negative binomial mixed regression log-link model. SF-36 data were transformed to a norm-based scale (NBS) using population matched data and analysed by mixed effects linear regression.

Results: Baseline DA in 266 patients was 5.43 (SD 1.27). Dynamic correlation revealed DA scores that omit foot joint scores were modest in their ability to capture foot synovitis over time. Despite relative stringency of SDAI and CDAI as remission criteria, a significant proportion of patients in remission had foot synovitis, ranging from 25-36% (Table 1). In patients in apparent remission, foot synovitis predicted transition from remission into relapse by up to 2-fold (Table 2), and the sustainability of remission markedly influenced progression of erosion scores (p=0.006) After adjustment for DA, foot synovitis was associated with significantly worse SF-36 physical functioning subscale (p=0.025). 

Table 1. Proportion of patients in remission

Table 2. The effect of foot synovitis on transition from remission to non-remission and vice versa

Conclusion:

DA measures that omit foot joints capture foot synovitis poorly. When used to define remission, a substantial proportion have foot synovitis which predicts relapse into non-remission and worse physical function. Foot synovitis influences sustainability of remission which in turn markedly influences radiographic progression. Presence of foot synovitis regardless of remission status should warrant consideration of escalation of therapy to improve long-term outcomes.

¹ Wechalekar MD et al. Arthritis Rheum 2012;64:1316-22.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/foot-synovitis-in-patients-with-rheumatoid-arthritis-in-apparent-remission-is-associated-with-unstable-remission-status-radiographic-progression-and-worse-long-term-functional-outcomes/