Page 11 - Recognizing axial spondyloarthritis - Janneke de Winter

Spondyloarthritis (SpA) is a heterogeneous form of inflammatory arthritis affecting the axial skeleton, including the sacroiliac joints and the spine, as well as peripheral joints and extra-articular sites. SpA has a prevalence of 0.5-1.0% (1,2). Traditionally, SpA was classified according to its phenotypic presentation as ankylosing spondylitis (AS), psoriatic arthritis (PsA), inflammatory bowel disease (IBD)-related SpA, reactive arthritis and undifferentiated SpA. Although SpA subtypes present heterogeneously, their common genetic background and strong familial aggregation (3–9), overlapping immunopathology (10–13), and largely similar response to treatment, justify handling them as one disease (14).
In 2009 the Assessment of SpondyloArthritis international Society (ASAS) developed sets of classification criteria reflecting the close resemblance of the different subtypes. Figure 1 shows the classification as axial SpA according to the ASAS criteria. The ASAS criteria distinguish between the axial and peripheral phenotype of SpA (15,16) and they were primarily developed to create homogeneous groups of patients for study purposes. The ASAS criteria classify a patient as axial SpA in the presence of back pain and 1) sacroiliitis on imaging (plain radiograph or magnetic resonance imaging (MRI)) and at least 1 other SpA feature, or 2) when a patient is HLA-B*27 positive and has at least 2 other SpA features. Patients with axial SpA can be classified as radiographic axial SpA, AS: with sacroiliitis on plain radiograph, or as non-radiographic axial SpA: when fulfilling either the clinical arm of the criteria or having SpA-specific sacroiliitis on MRI plus fulfilling one or two other criteria (Figure 1A). A patient classifies as having peripheral SpA in the presence of peripheral arthritis, enthesitis, or dactylitis plus at least one or two other SpA features, depending on the nature of the feature (Figure 1B). A recent meta-analysis showed good performance of the ASAS criteria when compared to a rheumatologists’ diagnosis (17).
AB
Figure 1. A The ASAS criteria for axial SpA. Patients are classified via the clinical arm (HLA-B*27 plus ≥ 2 other SpA features) or via the imaging arm (sacroiliitis on MRI or plain
GENERAL INTRODUCTION AND OUTLINE
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