Ankylosing spondylitis and axial spondyloarthritis: recent insights and impact of new classification criteria

Abstract

Development of the Assessment in Spondyloarthritis International Society (ASAS) classification criteria for axial spondyloarthritis (SpA) was one of the major breakthroughs in the field over the past decade. Despite some concerns related to the specificity of the criteria, they stimulated research into the early stage of the disease. This resulted in major advances in the understanding of the course of the disease, revealing predictors of progression, improvement in early diagnosis and treatment in axial SpA. In this review, we summarize the recent developments resulting from the introduction of the ASAS classification criteria for axial SpA and the implications for research and clinical practice.

Keywords: ASAS; Axial spondyloarthritis; ankylosing spondylitis; classification criteria; diagnosis.

Figure 1.

The spectrum of spondyloarthritis (SpA) and overlap (cross-sectional and longitudinal) between different SpA forms. IBD, inflammatory bowel disease.

Figure 2.

Assessment in Spondyloarthritis International Society (ASAS) classification criteria for axial spondyloarthritis (SpA). *Sacroiliitis on imaging refers to definite radiographic sacroiliitis according to the modified New York criteria or active sacroiliitis on magnetic resonance imaging according to the ASAS consensus definition. CRP, C-reactive protein; HLA-B27, human leucocyte antigen-B27; IBD, inflammatory bowel disease; NSAIDs, nonsteroidal anti-inflammatory drugs.

Figure 3.

Treatment algorithm for axial spondyloarthritis (SpA) based on the Assessment in Spondyloarthritis International Society/European League Against Rheumatism and American College of Rheumatology/Spondylitis Association of America/SpA Research and Treatment Network recommendations. bDMARDs, biologic disease-modifying antirheumatic drugs; csDMARDs, conventional synthetic disease-modifying antirheumatic drugs; IL-17A, interleukin-17A; NSAIDs, nonsteroidal anti-inflammatory drugs; TNF, tumour necrosis factor.

Figure 4.

(a) Approval status and year of approval for biological disease-modifying antirheumatic drugs (bDMARDs) by the European Medicines Agency for axial spondyloarthritis (SpA) in the EU and a number of other countries. (b) Approval status and year of approval for bDMARDs by the US Food and Drug Administration for SpA in the USA.