Background The incidence of fibromyalgia (FM), a chronic widespread pain syndrome, is highest in the first year after RA diagnosis.¹ These 12 months may represent a critical window during which acute inflammatory pain transitions to chronic non-inflammatory pain. To prevent this transition, more data are needed about the course and predictors of pain during this time.

Objectives 1) To describe the evolution of pain during the 12 months after RA diagnosis, and 2) to identify predictors of remaining pain and widespread pain (previously described as ‘fibromyalgic RA’)² at 12 months.

Methods Data were obtained from early RA patients in the Canadian Early Arthritis Cohort (CATCH), a prospective inception cohort. Primary outcomes were: 1) remaining pain above the Patient Acceptable Symptom State (PASS), defined as 4/10 on a pain intensity numerical rating scale,³ and 2) widespread pain, defined by tender joint count (TJC28) – swollen joint count (SJC28) ≥7.² Descriptive statistics were used to summarise the frequency of remaining pain and widespread pain over 12 months. Logistic regression models were used to identify predictors of remaining pain and widespread pain at 12 months. Variables forced into the multivariable models included age, sex, SJC28, ESR, depression, back pain, OA, sleep problems, HAQ-disability index (DI), MTX use, non-MTX conventional synthetic DMARD (csDMARD) use and NSAID use. Additional variables considered for inclusion via a backward selection process were race, education, income, FM, number of comorbidities and steroid use. Both models were adjusted for their respective baseline values.

Results 1270 patients were included, with mean (SD) age of 53.9 (14.5) years, symptom duration of 5.8 (3.0) months and baseline DAS28 of 5.0 (1.4). The percentage of patients with remaining pain decreased from 64% at baseline to 24% at 12 months. The percentage of patients with widespread pain decreased from 9% to 5%. The strongest predictors of 12 month remaining pain were sleep problems (highest quartile OR 2.2, 95% CI: 1.2 to 3.9), pain intensity >4/10 (OR 2.1, 95% CI: 1.3 to 3.4) and higher HAQ-DI score (OR 1.5, 95% CI: 1.1 to 2.0). The strongest predictors of 12 month widespread pain were higher HAQ-DI score (OR 1.8, 95% CI: 1.1 to 3.1) and higher number of comorbidities (OR 1.2, 95% CI: 1.0 to 1.5). Baseline non-MTX csDMARD use was associated with lower likelihood of widespread pain (OR 0.5, 95% CI: 0.3 to 0.8).

Conclusions Despite improvements in pain during the first year after RA diagnosis, 24% continued to report remaining pain above the PASS, and 5% reported widespread pain at 12 months. Patients at greatest risk for 12 month remaining pain were those with sleep problems, severe pain and disability at baseline. Patients at greatest risk for widespread pain were those with high baseline disability and many comorbidities. Baseline inflammation was not associated with 12 month pain outcomes.

References [1] Lee YC, et al. Ann Rheum Dis2013;72:649–54.

[2] Pollard LC, et al. Rheumatology2010;49:924–8.

[3] Tubach F, et al. Arthritis Care Res2012;64:1699–707.

Disclosure of Interest None declared