Looking into the new ASAS classification criteria for axial spondyloarthritis through the other side of the glass

Axial spondyloarthritis: concept, construct, classification and implications for therapy

The axial spondyloarthritis (axSpA) disease concept has undergone substantial change from when the entity ankylosing spondylitis was defined by the modified New York criteria in 1984. Developments in imaging, therapy and genetics have all contributed to changing the concept of axSpA from one of erosions in the sacroiliac joints to a spectrum of disease with and without changes evident on plain radiographs. Changes to the previously held concept and construct of the disease have also necessitated new classification criteria. The use of MRI, primarily of the sacroiliac joints, has substantially altered the diagnosis and differential diagnosis of axSpA. Many in the axSpA community believe that the current classification criteria lack specificity, and the CLASSIC study is underway to examine this area. Although much about the evolving axSpA disease concept is universally agreed, there remains disagreement about operationalizing aspects of it, such as the requirement for the objective demonstration of axial inflammation for the classification of axSpA. New imaging technologies, biomarkers and genetics data will probably necessitate ongoing revision of axSpA classification criteria. Advances in our knowledge of the biology of axSpA will settle some differences in opinion as to how the disease concept is applied to the classification and diagnosis of patients.

Non-Radiographic Axial Spondyloarthritis (nr-axSpA): Advances in Classification, Imaging and Therapy

Non-radiographic axial spondyloarthritis (nr-axSpA) is a recently described form of axial inflammatory arthritis that has not caused substantial erosive damage to the sacroiliac joints. Nr-axSpA is associated with significant impairment in quality of life and, in a proportion of patients, it can evolve into ankylosing spondylitis (AS, also termed radiographic axSpA). The identification in the clinic of nr-axSpA has been made possible by advances in magnetic resonance imaging (MRI). Classification criteria for nr-axSpA have been proposed but there remains discussion in the international community regarding this. Studies are ongoing to further define the classification and diagnosis of nr-axSpA. There is much further research required regarding the optimal use of MRI in nr-axSpA, including distinguishing sacroiliac MRI changes in the normal population and the definition of a positive MRI in spinal disease. Non-steroidal anti-inflammatory drugs and physiotherapy are the core first-line therapy for nr-axSpA. Tumour necrosis factor inhibitors also play a very important role in treatment of patients with active nr-axSpA who do not respond to first-line therapy. Agents directed at interleukin-17, interleukin-23 and Janus kinase inhibitors are proving effective in AS with ongoing and planned studies in nr-axSpA. A great deal of active research is being undertaken in classification, imaging and therapy in nr-axSpA and so the future for improving the lives of patients with nr-axSpA is promising.

Radiologic approach to axial spondyloarthritis: where are we now and where are we heading?

Current emphasis on diagnosing axial spondyloarthritis (axSpA) in early stage enforced the search for sensitive and specific diagnostic algorithms with the use of imaging methods. The aim of this review was to summarise current recommendations concerning the use of imaging techniques in diagnostics and monitoring of axSpA as well as to outline possible future directions of the development in this field. MEDLINE database was searched between March and April 2018. In the first phase, such keywords were applied: ‘ASAS’, ‘EULAR’, ‘ASAS-EULAR’, ‘ASAS/OMERACT’, ‘axial spondyloarthritis’, while in the second step: ‘axial spondyloarthritis’, ‘ankylosing spondylitis’, ‘magnetic resonance imaging’, ‘computed tomography’, and ‘radiography’, ‘imaging’. An up-to-date summary of European League Against Rheumatism (EULAR) recommendations enriched with recent updates of Assessment of Spondyloarthritis International Society (ASAS) diagnostic criteria regarding imaging in axSpA course was created. Moreover, we outlined the role of new in this field, promising imaging techniques, such as diffusion-weighted imaging and dynamic contrast-enhanced sequences in magnetic resonance imaging (MRI) or low-dose computed tomography (CT). As precise monitoring of axSpA activity is vital, we reviewed the most precise methods: semiquantitative scores (e.g., Spondyloarthritis Research Consortium of Canada scores or CT Syndesmophyte Score) and quantitative analysis of MRI-based apparent diffusion coefficient or perfusion maps and enhancement curves. According to EULAR and ASAS recommendations, radiography and MRI still remain basic methods of axSpA diagnostics and monitoring. However, the knowledge of state-of-the-art international guidelines combined with the awareness of emerging imaging methods is the key to effective management of axSpA.

Classification Terminology and Definitions in Reporting of MRI in Axial Spondyloarthritis

Spondyloarthritis (SpA) is a group of chronic inflammatory conditions which severely impact quality of life. Several criteria have been developed in the past to aid the diagnosis of SpA based on symptoms and radiographic changes during the course of the disease. However, it takes several years before structural changes manifest on conventional radiographs, leading to a diagnostic delay of 6 to 10 years. The use of MRI and its incorporation into the Assessment of Spondyloarthritis (ASAS) criteria, has radically changed the diagnosis of SpA in the last decade by allowing visualisation of both active and chronic inflammatory changes and enabling clinicians to recognise SpA during it’s early stage and initiate treatment. An understanding of the various terminology used in the divisions of disease presentations and their relevant imaging findings are key, along with the use of clear definitions of structural and inflammatory changes on MRI, in ensuring accurate diagnosis and classification of SpA.

Progress of genome-wide association studies of ankylosing spondylitis

Ankylosing spondylitis (AS) is an immune-mediated arthritis which primarily affects the spine and sacroiliac joints. Significant progress has been made in discovery of genetic associations with AS by genome-wide association studies (GWAS) over past decade. These findings have uncovered novel pathways involved pathogenesis of the disease and have led to introduction of novel therapeutic treatments for AS. In this Review, we discuss the genetic variations associated with AS identified by GWAS, the major pathways revealed by these AS-associated variations and critical cell types involved in AS development.

Progression of Nonradiographic Axial Spondyloarthritis to Ankylosing Spondylitis: A Population-Based Cohort Study

OBJECTIVE

The long-term outcome of patients with nonradiographic axial spondyloarthritis (SpA) is unclear, particularly whether few or most progress to ankylosing spondylitis (AS). Our objective was to examine the progression to AS in a population-based inception cohort of patients with nonradiographic axial SpA.

METHODS

The Rochester Epidemiology Project (REP) is a longstanding population-based study of health in the residents of Olmsted County, Minnesota. We searched the REP from 1985 to 2010 using diagnostic and procedural codes for back pain, HLA-B27, and magnetic resonance imaging of the pelvis, and we performed detailed chart reviews to identify subjects who fulfilled the Assessment of SpondyloArthritis international Society classification criteria for axial SpA but did not have AS. We followed these subjects from disease onset to March 15, 2015, and used survival analysis to measure the time to progression to AS.

RESULTS

After screening 2,151 patients, we identified 83 subjects with new-onset nonradiographic axial SpA. Over a mean follow-up of 10.6 years, progression to AS occurred in 16 patients. The probability that the condition would remain as nonradiographic axial SpA at 5, 10, and 15 years was 93.6%, 82.7%, and 73.6%, respectively. There was more frequent and more rapid progression among subjects in the imaging arm (n = 18) than among those in the clinical arm (n = 65) (28% versus 17%; hazard ratio 3.50 [95% confidence interval 1.15-10.6], P = 0.02).

CONCLUSION

Progression to AS occurred in a minority (26%) of patients with nonradiographic axial SpA over as long as 15 years of follow-up. This suggests that the classification criteria for nonradiographic axial SpA identifies many patients in whom the condition is unlikely to progress to AS or that nonradiographic axial SpA represents a prolonged prodromal state that takes longer to evolve to AS and thus requires longer follow-up.

ASAS classification criteria for axial spondyloarthritis: time to modify

The relationship between ankylosing spondylitis and the recently proposed entity called axial spondyloarthritis with its radiographic and non-radiographic forms that have been defined by the Assessment of Spondyloarthritis International Society (ASAS) criteria for axial spondyloarthritis (axSpA), is currently being debated. The Food and Drug Agency (FDA) had criticized the ASAS criteria and the studies which used these criteria to enroll patients in a clinical trial of certolizumab and adalimumab for the treatment of non-radiographic axial spondyloarthritis. The primary aim of classification criteria is to create homogenous patient populations for basic and clinical research. But the multi-arm construct of the ASAS criteria is a potential source of heterogeneity reducing their utility. Criteria sets should be regarded as dynamic concepts open to modifications or updates as our knowledge advances. We provide evidence to conclude that it is time to modify the ASAS Criteria for axSpA, and we propose some of the steps that can be taken to start moving forward in improving the validity of these criteria.