The field of spondyloarthritis (SpA) has experienced major progress in the last decade, especially with regard to new treatments, earlier diagnosis, imaging technology and a better definition of outcome parameters for clinical trials. In the present work, the Assessment in SpondyloArthritis international Society (ASAS) provides a comprehensive handbook on the most relevant aspects for the assessments of spondyloarthritis, covering classification criteria, MRI and x rays for sacroiliac joints and the spine, a complete set of all measurements relevant for clinical trials and international recommendations for the management of SpA. The handbook focuses at this time on axial SpA, with ankylosing spondylitis (AS) being the prototype disease, for which recent progress has been faster than in peripheral SpA. The target audience includes rheumatologists, trial methodologists and any doctor and/or medical student interested in SpA. The focus of this handbook is on practicality, with many examples of MRI and x ray images, which will help to standardise not only patient care but also the design of clinical studies.

Background: Magnetic resonance imaging (MRI) of sacroiliac joints has evolved as the most relevant imaging modality for diagnosis and classification of early axial spondyloarthritis (SpA) including early ankylosing spondylitis. Objectives: To identify and describe MRI findings in sacroiliitis and to reach consensus on which MRI findings are essential for the definition of sacroiliitis. Methods: Ten doctors (two radiologists and eight rheumatologists) from the ASAS/OMERACT MRI working group reviewed and discussed in three workshops MR images depicting sacroiliitis associated with SpA and other conditions which may mimic SpA. Descriptions of the pathological findings and technical requirements for the appropriate acquisition were formulated. In a consensual approach MRI findings considered to be essential for sacroiliitis were defined. Results: Active inflammatory lesions such as bone marrow oedema (BMO)/osteitis, synovitis, enthesitis and capsulitis associated with SpA can be detected by MRI. Among these, the clear presence of BMO/osteitis was considered essential for defining active sacroiliitis. Structural damage lesions such as sclerosis, erosions, fat deposition and ankylosis can also be detected by MRI. At present, however, the exact place of structural damage lesions for diagnosis and classification is less clear, particularly if these findings are minor. The ASAS group formally approved these proposals by voting at the annual assembly. Conclusions: For the first time, MRI findings relevant for sacroiliitis have been defined by consensus by a group of rheumatologists and radiologists. These definitions should help in applying correctly the imaging feature “active sacroiliitis by MRI” in the new ASAS classification criteria for axial SpA.

Objectives To review and update the existing definition of a positive MRI for classification of axial spondyloarthritis (SpA). Methods The Assessment in SpondyloArthritis International Society (ASAS) MRI working group conducted a consensus exercise to review the definition of a positive MRI for inclusion in the ASAS classification criteria of axial SpA. Existing definitions and new data relevant to the MRI diagnosis and classification of sacroiliitis and spondylitis in axial SpA, published since the ASAS definition first appeared in print in 2009, were reviewed and discussed. The precise wording of the existing definition was examined in detail and the data and a draft proposal were presented to and voted on by the ASAS membership. Results The clear presence of bone marrow oedema on MRI in subchondral bone is still considered to be the defining observation that determines the presence of active sacroiliitis. Structural damage lesions seen on MRI may contribute to a decision by the observer that inflammatory lesions are genuinely due to SpA but are not required to meet the definition. The existing definition was clarified adding guidelines and images to assist in the application of the definition. Conclusion The definition of a positive MRI for classification of axial SpA should continue to primarily depend on the imaging features of ‘active sacroiliitis’ until more data are available regarding MRI features of structural damage in the sacroiliac joint and MRI features in the spine and their utility when used for classification purposes.

Objective To study the relationship between spinal mobility, radiographic damage of the spine and spinal inflammation as assessed by MRI in patients with ankylosing spondylitis (AS). Methods In this subanalysis of the Ankylosing Spondylitis Study for the Evaluation of Recombinant Infliximab Therapy cohort, 214 patients, representing an 80% random sample, were investigated. Only baseline data were used. MRI inflammation was assessed by the AS spinal MRI activity (ASspiMRI-a) score, structural damage by the modified Stoke AS Spine Score (mSASSS) and spinal mobility by the linear definition of the Bath Ankylosing Spondylitis Metrology Index (BASMI). Univariate correlations were calculated on baseline values using Spearman rank correlation. Independent associations between the variables of interest were investigated by multivariate linear regression analysis. Associations with clinical disease activity, C-reactive protein, disease duration, age, gender, body mass index and HLA-B27 status were also investigated. Subanalyses were performed according to disease duration. Results BASMI correlated moderately well with mSASSS (Spearman's ρ=0.6) and weakly with ASspiMRI-a (ρ=0.3). A best-fit model for BASMI included both mSASSS (regression coefficient (B)=0.865, p3 years B was greater for mSASSS than for ASspiMRI-a (0.924 vs 0.156). Conclusion Spinal mobility impairment in AS is independently determined both by irreversible spinal damage and by reversible spinal inflammation. Spinal mobility impairment is more influenced by spinal inflammation in early disease, and by structural damage in later disease.

Objective The aim of this study was to define characteristic MRI findings in the spine of patients with axial spondyloarthritis (SpA) and provide a definition of a positive spinal MRI for inflammation and structural changes. Methods Technical details of spinal MRI and the description of spinal lesions of both inflammation and structural changes were discussed in consecutive meetings of 10 experts of the Assessment in SpondyloArthritis international Society (ASAS). The discussions aimed at a broad consensus on definitions of ‘a positive spinal MRI’ for both types of lesions and were backed up by a systematic literature search. Results A total of six different types of lesions were described for inflammation—anterior/posterior spondylitis, spondylodiscitis, arthritis of costovertebral joints, arthritis of zygoapophyseal joints and enthesitis of spinal ligaments—and another four for structural changes—fatty deposition, erosions, syndesmophytes and ankylosis. In the literature review, four relevant papers were identified. Anterior/posterior spondylitis and fat depositions at vertebral edges were considered as the most typical findings in SpA. Based on expert consensus and taking the literature review into consideration, a positive spinal MRI for inflammation was defined as the presence of anterior/posterior spondylitis in ≥3 sites. Evidence of fatty deposition at several vertebral corners was found to be suggestive of axial SpA, especially in younger adults. ASAS members (n=56) approved these definitions by voting in January 2010. Conclusions This consensus statement gives clear descriptions of disease-related spinal lesions and of definitions of a positive spinal MRI for inflammatory lesions (spondylitis) and structural changes (fat deposition). These definitions can be used to describe findings of spinal MRI in patients with SpA in daily practice and clinical studies.

Purpose To evaluate the potential of etanercept versus sulfasalazine to reduce active inflammatory lesions on whole-body MRI in active axial spondyloarthritis with a symptom duration of less than 5 years. Methods Patients were randomly assigned to etanercept (n=40) or sulfasalazine (n=36) treatment over 48 weeks. All patients showed active inflammatory lesions (bone marrow oedema) on MRI in either the sacroiliac joints or the spine. MRI was performed at weeks 0, 24 and 48 and was scored for active inflammatory lesions in sacroiliac joints and the spine including posterior segments and peripheral enthesitis by two radiologists, blinded for treatment arm and MRI time point. Results In the etanercept group, the reduction of the sacroiliac joint score from 7.7 at baseline to 2.0 at week 48 was significantly (p=0.02) larger compared with the sulfasalazine group from 5.4 at baseline to 3.5 at week 48. A similar difference in the reduction of inflammation was found in the spine from 2.2 to 1.0 in the etanercept group versus from 1.4 to 1.3 in the sulfasalazine group between baseline and week 48, respectively (p=0.01). The number of enthesitic sites also improved significantly from 26 to 11 in the etanercept group versus 24 to 26 in the sulfasalazine group (p=0.04 for difference). 50% of patients reached clinical remission in the etanercept group versus 19% in the sulfasalazine group at week 48. Conclusion In patients with early axial spondyloarthritis active inflammatory lesions detected by whole-body MRI improved significantly more in etanercept versus sulfasalazine-treated patients. This effect correlated with a good clinical response in the etanercept group.