The last two decades have seen major advances in the understanding of axial SpA – a chronic, heterogeneous, inflammatory syndrome that primarily affects axial entheses and joints, especially the fibro-cartilagenous bone. This issue of Rheumatology appraises the literature on the axial SpA spectrum, discusses the ongoing challenges in diagnosis, the impact of sex and co-morbidities, and summarizes recent findings in pathogenesis and treatment strategies. We have picked out some of the key papers relevant to diagnosis and summarised them on this page.
In recent years, significant progress has been made in improving the early diagnosis of spondyloarthritides (SpA), including axial SpA. Nonetheless, there are still issues related to the application of classification criteria for making the primary diagnosis of SpA in the daily practice. There are substantial conceptional and operational differences between the diagnostic vs classification approach. Although it is not possible to develop true diagnostic criteria for natural reasons as discussed in this review, the main principles of the diagnostic approach can be clearly defined: consider the pre-test probability of the disease, evaluate positive and negative results of the diagnostic test, exclude other entities, and estimate the probability of the disease at the end. Denis Poddubnyy describes the diagnostic process as a “diagnostic scale”, whereby one should weigh positive test results and present clinical features against negative test results and the presence of an alternative explanation for the symptoms. Even when all tests have been conducted, a diagnosis of axial SpA may remain uncertain. However, we know that these conditions change and evolve over time. If a diagnosis of axial SpA cannot be confirmed but clinical suspicion remains high, consider a follow‑up MRI to monitor for any potential future inflammatory changes. Classification criteria should only be applied to patients with an established diagnosis and aimed at the identification of a homogeneous group of patients for the conduction of clinical research.
Axial spondyloarthritis is a heterogeneous inflammatory condition with variable clinical presentations and outcomes. The complexity of its diagnosis and absence of biomarkers hamper the development of diagnostic criteria with the risk of misuse of the available classification criteria in clinical practice and its consequences. Axial spondyloarthritis should be regarded as a continuum in which some patients, but not all, will have a more severe phenotype characterized by progression into new bone formation and joint fusion. Growing understanding of the factors that might drive disease progression and treatment response will allow for better characterization of treatment options and outcome for each affected individual. The aim of this review is to update the current evidence of what is axial spondyloarthritis and to highlight the need to focus on the concept rather than its classification.
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