POS0992 CLINICAL AND IMAGING FEATURES IN SPONDYLOARTHRITIS PATIENTS WITH AND WITHOUT HLA-B27 AND HLA-B51: A VALIDATION COHORT

BackgroundDespite being commonly expressed in the general population, the human leucocyte antigen (HLA)-B27 allele strongly increases the susceptibility to develop spondyloarthritis (SpA). Likewise, the association between the HLA-B51 allele and the development of Behçet’s disease is well documented. In a previous pilot study, we identified similarities and differences in patients with axial or peripheral SpA according to the presence of HLA-B51 only, HLA-B27 only or neither of the two.ObjectivesTo investigate the clinical and imaging findings of SpA patients according to the absence or presence of HLA-B27 or HLA-B51 in an independent validation cohort.MethodsWe retrospectively analyzed patients with axial or peripheral SpA, according to the ASAS criteria, referring to our institution between 2020 and 2021. All patients had been tested for HLA-B alleles. Patients with HLA-B51 haplotype and fulfilling the criteria for Behçet’s disease were excluded.ResultsThe independent validation cohort included 185 patients and was comparable to the original cohort of 236 patients with regard to age, gender, age at diagnosis and symptom duration. In line with the findings in the original cohort we observed that aphtous lesions were more prevalent in patients with HLA-B51 (p< 0.001) while inflammatory bowel disease was more prevalent in the double negative group (p=0.0006). Unlike the original cohort, patients of the validation cohort did not show a different prevalence of inflammatory back pain (IBP) at disease onset or in the disease course based on the HLA status. A sub-analysis by gender demonstrated a comparable prevalence of IBP in males and females within the 3 groups. As novel finding, we observed that enthesitis and psoriasis were significantly more prevalent in the double negative group compared to the B27 and B51 groups (p=0.004) and their prevalence did not differ when comparing B27 and B51 groups. With regard to imaging in patients with axial manifestations, in the original cohort we observed that sacroiliitis, assessed by X-ray or magnetic resonance imaging (MRI), were more prevalent in double negative and HLA-B27 patients, compared to HLA-B51 patients and the latter showed a significant negative association with sacroiliitis on imaging (OR 0.342 CI 0.189-0.619 pConclusionOur findings underscore the clinical and radiological heterogeneity of patients with SpA and HLA-B51 alone or neither HLA-B27 nor HLA-B51 compared to those with HLA-B27 only and underline the need to explore further this area by means of registry data with large real-life cohorts.Disclosure of InterestsNone declared