BACKGROUND: The relationship between non-radiographic axial spondyloarthritis (nr-axSpA) and ankylosing spondylitis (AS) is currently debated. Using observational data from the South Swedish Arthritis Treatment Group register, we thus aimed to compare clinical development and treatment adherence between nr-axSpA and AS patients during three years of anti-TNF (tumor necrosis factor) therapy in clinical practice, and to explore the impact of inflammatory activity measured by CRP (C-reactive protein) at treatment initiation.

METHODS: Nr-axSpA and AS patients (n = 86/238) in southern Sweden, commencing anti-TNF therapy 1999-2011, were followed during three years. Anti-TNF cessation was defined as stopping therapy, without restarting another anti-TNF agent within three months. Differences in the three year developments of patient's visual analogue scale (VAS) scores for global health and pain, EuroQol 5-Dimensions utility, evaluator's global disease activity assessment, CRP, and ESR (erythrocyte sedimentation rate) were assessed by repeated ANOVA. Anti-TNF adherence was compared by Log rank test and Cox regression. In a subanalysis, the same outcomes were studied after splitting both groups into patients with/without baseline CRP elevation.

RESULTS: Nr-axSpA patients were more often female and had lower acute phase reactants at baseline. Apart from CRP, which remained lower in the nr-axSpA group throughout follow-up (p = 0.004), no between-group differences were detected regarding clinical developments (p >0.1 for all comparisons) or anti-TNF adherence (hazard ratio: 1.1 (95 % CI 0.7 to 1.8) for the nr-axSpA vs. AS group) during three years. Elevated baseline CRP was similarly associated with superior clinical outcomes and treatment adherence in both groups.

CONCLUSIONS: With the exception of constantly lower CRP levels in the nr-axSpA group, three years anti-TNF therapy resulted in similar clinical outcomes and treatment adherence in nr-axSpA and AS patients, thus strengthening the hypothesis that these diagnoses represent different aspects/phases of the same disease.

OBJECTIVES: To compare the 28-joint Disease Activity Score (DAS28) and its components in patients with rheumatoid arthritis (RA) with and without concomitant fibromyalgia (FM), and to investigate the use of biological treatment in the two groups.

METHOD: Questionnaires developed to diagnose FM were handed out among RA patients during their planned visits. Values for DAS28 were obtained from the DANBIO registry. Demographic data and data on patients' medical treatment, disease duration, serological and radiological status were retrieved from patients' files. The χ(2) test and an unpaired t-test were applied to investigate group differences in the use of biological therapy, baseline characteristics, patient-reported outcomes, and DAS28 between groups when appropriate.

RESULTS: Questionnaires were completed by 162 out of 264 (61%) patients. Twenty-five patients (15.4%) with concomitant FM were identified. No group differences were found regarding disease duration, age, gender, and serological status. Of the RA patients with concomitant FM, 64% were treated with biological therapy vs. 32% of RA patients without concomitant FM (p = 0.002). The mean DAS28 in the FM group was 4.4 compared to 2.9 in the non-FM group (p < 0.001). Elevated DAS28 in the FM group resulted from a high tender joint count (p = 0.003) and a high visual analogue scale (VAS)-global score (p < 0.001). Erosions were more frequent in the non-FM group (p = 0.04).

CONCLUSIONS: Concomitant FM in patients with RA is associated with a higher DAS28 due to subjective parameters and with the more frequent use of biological treatments. This raises the question of whether the more frequent use of biologics in these patients is justified by inflammation, or is instead due to persistent pain and other centrally mediated symptoms.