In the multicentre Screening for Axial SpA in Psoriasis, Iritis (AAU), and Colitis cohort, 48% of people with psoriasis, AAU or colitis, ≤45 years of age with ≥3 months undiagnosed back pain were diagnosed with axial SpA if using a three-stage evaluation approach (clinical evaluation, laboratory results [HLA-B27, CRP] and radiography, MRI); 69% were diagnosed with axial SpA after the clinical evaluation alone. These figures suggest that many opportunities to identify, diagnose and treat axial SpA are being missed.
The following clinical SpA features were non-discriminatory between axial SpA/not axial SpA: NSAID response, family history of SpA, heel enthesitis, peripheral arthritis, dactylitis. This effect was particularly noteworthy in patients with lower degree of symptomatology (back pain severity <5/10), short symptom duration (<5 years) and in females. In a prospective cohort with a high pre-test probability of axial SpA certain clinical SpA features were not helpful in discriminating a diagnosis of SpA.
Clinical and patient-reported outcomes of 2420 patients with axial SpA from 83 centres were collected by the British Society for Rheumatology Biologics Register in Ankylosing Spondylitis (BSRBR-AS). This study demonstrates that one in three patients with axial SpA have at least one EAM of axial SpA; however, 84% have a single EAM, suggesting that there are unrelated pathogenic mechanisms. AAU was significantly associated with HLA-B27; however, patients with psoriasis and IBD had lower rates of HLA-B27 positivity than the overall cohort. The presence of EAMs does not increase the likelihood of patients being started on a TNF-inhibitor; however, EAMs do influence TNF-inhibitor choice. Patients with previous AAU and IBD are more likely to be prescribed adalimumab and less likely to receive etanercept, consistent with the superior efficacy of monoclonal TNF-inhibitors for these indications. Future longitudinal analysis will determine whether EAMs influence TNF-inhibitor survival and whether or not individual TNF-inhibitors protect patients from incident or flares of existing EAMs.
A total of 1729 patients with axial SpA were included in the analyses (mean age: 56 years; 46% female), of whom 6%, 10% and 9% had current IBD, psoriasis, and AAU, respectively; and 9%, 15% and 27% had ever had IBD, psoriasis, and AAU, respectively. Ever having presence of IBD and history of psoriasis were significantly associated with higher level of disease activity. Ever presence of psoriasis was also associated with higher level of functional impairment, whereas current AAU was significantly associated with lower disease activity. Patients with current IBD or psoriasis received biological and conventional synthetic disease-modifying anti-rheumatic drugs more frequently, as well as systemic steroids. AAU was associated with a higher use of conventional synthetic disease-modifying anti-rheumatic drugs only.
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