Abstract
OBJECTIVE: Patients with early rheumatoid arthritis (RA) may present with more tender than swollen joints, which can persist. Elevated tender-swollen joint difference (TSJD) is often challenging, because there may be multiple causes and it may contribute to overestimating disease activity. Little is known about the phenotype and impact of TSJDs on patient function. Our objective was to evaluate the impact of TSJD on functional outcomes in early RA and to see whether associations vary by joint size. METHODS: Data were from patients with active, early RA (≤12 months) enrolled in the Canadian Early Arthritis Cohort, who completed assessments of general function (Multidimensional Health Assessment Questionnaire [MDHAQ]), upper extremity (UE) function (Quality of Life in Neurological Disorders [Neuro-QoL] UE scale), and work/activity impairment (Work Productivity and Activity Impairment RA) over their first year of follow-up. A total of 28 joint counts were performed. TSJDs were calculated. Adjusted associations between TSJDs and functional outcomes were estimated in separate multivariable linear mixed effects models. Separate analyses were performed for large- versus small-joint TSJD. RESULTS: Patients (N = 547) were 70% female, mean age 56 (SD 15) years, mean disease duration 5.3 (SD 2.9) months. At baseline, 287 (52%) had TSJD >0 (43% involved large joints and 34% small joints), decreasing to 32% at 12 months. A one-point increase in TSJD was significantly associated with worse function (MDHAQ: adjusted mean change 0.10, 95% confidence interval [CI] 0.08-0.13; Neuro-QoL UE function T score: adjusted mean change -0.59, 95% CI -0.76 to -0.43; and greater work impairment: adjusted mean change 1.95%, 95% CI 0.85%-3.05%). Higher large-joint TSJDs were associated with the worst functional outcomes. CONCLUSION: Having more tender than swollen joints is common in early RA and is associated with worse function, most notably when involving large joints. Early identification and targeted intervention strategies may be needed.