Page 23 - Recognizing axial spondyloarthritis - Janneke de Winter

INTRODUCTION
Spondyloarthritis (SpA) is a chronic inflammatory disease with a heterogeneous clinical presentation which can include axial, peripheral, and extra-articular (skin, gut, and eye) disease manifestations. Traditionally, SpA was divided in subtypes based on phenotypic presentation. However, recent insights in the taxonomy of the disease do not justify this phenotypic classification as data from family and genetic studies (1–5), response to treatment (6–9), and immunopathology (10– 13) rather suggest a single disease with overlapping but distinct pathophysiology for axial versus peripheral disease (14). This taxonomy parallels the Assessment of SpondyloArthritis international Society (ASAS) classification criteria distinguishing axial and peripheral SpA (15,16).
One potential issue with the classification into axial versus peripheral SpA is that approximately 30% of the SpA patients have both axial and peripheral involvement (15,17). The ASAS criteria pre-specify that patients with back pain and peripheral disease manifestations (arthritis, enthesitis and/or dactylitis) are classified as axial SpA, independently of which disease manifestations predominates in terms of disease activity and burden. When inappropriately applied by different stakeholders (including not only rheumatologists but also other health care professionals, regulators, and payers), this classification may thus potentially lead to an underestimation of the prevalence and disease burden of peripheral disease in SpA. Therefore, this study aimed to systematically assess the prevalence and burden of peripheral disease in axial and peripheral SpA as defined by the ASAS criteria in a large, real-life observational cohort.
METHODS
Patient cohort
Patients presenting on the specialized SpA outpatient clinic of the Department of Clinical Immunology and Rheumatology at the Academic Medical Center/ University of Amsterdam between June 2007 and August 2012 (n=272) and of the University Medical Center Utrecht between January 2011 and August 2012 (n=42) were included in this real-life prospective observational cohort, as approved by the local Medical Ethics Committees. Patients were ≥ 18 years old, had both a clinical diagnosis of SpA according to the expert opinion of the treating rheumatologist and fulfilled the ASAS criteria (15,18). Demographic and disease characteristics, HLA-B27 and X-rays of the sacroiliac joints were collected at the first visit. X-rays were scored locally according to the modified New York (mNY) criteria (19). The patient’s and physician’s global assessment of disease activity, Bath Ankylosing Spondylitis Disease Activity (BASDAI) (20), Ankylosing Spondylitis Disease Activity Score (ASDAS) based on the C-reactive protein (CRP) (21), 66/68 swollen joint count (SJC) and tender joint count (TJC), Schober, chest expansion, CRP, erythrocyte sedimentation rate (ESR), and medication use were measured and
PERIPHERAL DISEASE IN AXIAL SPA
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