Background/Purpose: The definition for early spondyloarthritis (SpA) implies the correct identification of the initial symptom of SpA. There is currently no consensus on whether only musculoskeletal manifestations (MM) or also extra-MM (EMM) should be considered as the onset of SpA.

Objectives: a) To describe the initial symptom (either MM or EMM) in the different SpA subtypes; b) to describe the initial symptom stratified by the clinical diagnosis and by the presence of HLA-B27; c) to analyze the clinical factors associated with different forms of initiation.

Methods: Observational, cross-sectional and multicenter study, including patients with a diagnosis of SpA (Ankylosing Spondylitis (AS), AS associated with Psoriasis (AS-Pso), AS associated with Inflammatory Bowel Disease (AS-IBD), Psoriatic Arthritis (PsA), Reactive Arthritis (ReA), Juvenile Spa (Juv-SpA), Arthritis associated with IBD (A-IBD) and undifferentiated SpA (u-SpA)) from REGISPONSER and RESPONDIA registries. Investigators responses to the question “Indicate the first sign or symptom attributable to the disease” have been recorded. The date of appearance of each MM and EMM feature was collected, allowing to determine the first symptom(s) in each patient. Differences in the first symptom across diagnosis and between HLA-B27 carriers were compared using the chi-square test. Finally, factors associated with the most prevalent initial symptom were evaluated.

Results: A total of 4411 patients were included. AS (54.9%), PsA (18.7%) and uSpA (11.1%) were the most prevalent diagnosis. In the overall population, low back pain (60.3%) was the most prevalent initial symptom followed by buttock pain (35.3%) and lower limbs arthritis (39.9%). The percentage of patients who started the disease with each symptom according to the diagnosis is represented in Figure 1.

In AS patients, the absence of HLA-B27 lead to an increment in the probability of initiating the disease with cervical pain (25.6% vs. 15.5%), enthesitis (18.8% vs. 12.4%) and coxitis (15.7% vs. 8.4%) in comparison with HLA-B27 positives. In PsA, the initiation with upper limb arthritis (61% vs. 38.4%) and psoriasis (62.1% vs. 37%) was more prevalent in HLA-B27 negatives, while the initiation with low back pain (22.1% vs. 38.4%) and buttock pain 13.6% vs. 28.8%) was more prevalent in HLA-B27 positives. In AS-Pso, the absence of HLA-B27 was more frequently associated with peripheral features and psoriasis as first symptom.

In the whole population, factors associated with cervical pain vs. low back pain as first symptom were cutaneous psoriasis, negative HLA-B27 and peripheral involvement (arthritis, enthesitis and dactylitis). On the other hand, factors associated with upper limbs arthritis vs. lower limbs arthritis as first symptom were female gender, cutaneous psoriasis, HLA-B27 negative and absence of axial symptoms.

Conclusion: In this SpA population, the most prevalent initial symptoms were musculoskeletal, with differences across diagnosis and depending on the presence of HLA-B27 antigen. In AS patients the absence of the HLA-B27 seems to be associated with cervicalgia and peripheral involvement as first symptom, while in PsA it was associated with upper limbs involvement as initial symptom.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/how-do-spondyloarthritis-start-identification-of-the-first-signs-or-symptoms-according-to-diagnosis-and-hla-b27-data-from-regisponser-and-respondia-registries/