Background The number of clinical SpA-features plays an important role in the Assessment of SpondyloArthritis international Society (ASAS) modified Berlin algorithm for the diagnostic work-up of patients (pts) with a suspicion of axial SpA (axSpA).
Objectives To investigate whether all pts with short duration chronic back pain (CBP) and multiple SpA-features are always diagnosed as axSpA by the rheumatologist and to describe the features of these patients.
Methods The SPondyloArthritis Caught Early (SPACE)-cohort includes CBP pts (≥3 months, ≤2 years, onset <45 years) from various European rheumatology centres. Baseline data were used for the analyses. Following a fixed protocol all pts underwent a full diagnostic work-up consisting of performance of MRI and radiographs of sacroiliac joints (MRI-SI and X-SI), acute phase reactants, HLA-B27 testing, and assessment of other SpA-features (inflammatory back pain (IBP), good response to NSAIDs, family history for SpA, peripheral arthritis, dactylitis, enthesitis, uveitis, inflammatory bowel disease (IBD), and psoriasis). Local radiologists or rheumatologists from the different centres interpreted MRI-SI and X-SI on presence of sacroiliitis (yes/no) using global assessment as part of routine clinical practice. Total number of SpA-features was calculated excluding sacroiliac imaging and HLA-B27 status. The treating rheumatologist provided clinical diagnosis of pts and the ASAS-criteria for axSpA were used for classification.
Results A total of 522 pts were analysed in this study: before sacroiliac imaging and HLA-B27 testing 164/522 (31.4%) pts had no or 1 SpA-feature, 148/522 (28.4%) pts had 2 SpA-features, 85/522 (16.3%) pts had 3 SpA-features, and 125/522 (23.9%) pts had ≥4 SpA-features respectively. IBP, good response to NSAIDs, and positive family history for SpA were most common in all subgroups (0 or 1 feature: 26.8%, 8.5%, and 16.5% of pts; 2 features: 72.3%, 34.5%, 39.9%; 3 features: 87.1%, 60.0%, 54.1%; ≥4 features: 94.4%, 83.2%, 68.0% respectively). Of the pts with 2 and 3 SpA-features with negative X-SI 20/132 (15.2%) and 9/78 (11.5%) did not have axSpA diagnosis despite being HLA-B27+ (Figure 1). All pts with ≥4 SpA-features and X-SI+ (n=28) were diagnosed with axSpA. In contrast to what would be expected by following the modified Berlin algorithm for pts with ≥4 SpA-features, 18/94 pts (19.1%) with negative imaging (of which 4 HLA-B27+), were not diagnosed with axSpA by their rheumatologist. Multivariate regression analysis of presence of SpA-features identified MRI-SI+ (OR 41.7;95%CI 17.3.1–100.5), X-SI+ (OR 31.5;95%CI 3.1–321.0), HLA-B27+ (OR 4.7;95%CI 2.5–8.6), uveitis (OR 4.3;95%CI 1.5–12.7), IBP (OR 2.5;95%CI 1.4–4.7), heel enthesitis (OR 5.5;95%CI 2.7–11.4), IBD (OR 3.2;95%CI 1.2–8.8), elevated CRP/ESR (OR 2.7;95%CI 1.4–5.3), and psoriasis (OR 2.5;95%CI 1.0–6.0) as significant independent predictors of axSpA diagnosis.
Conclusions In this cohort of pts with CBP having numerous SpA-features did not automatically lead to a clinical axSpA diagnosis but positive imaging was the main driving factor to diagnosis of axSpA.
Disclosure of Interest None declared