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OP0272 Prevalence of Structural Lesions MRI-Spine in Patients with (Possible) Axial Spondyloarthritis (AXSPA) Included in the Space-Cohort

Background Little is known about the prevalence of structural lesions (erosions (ERO), (bridging) syndesmophytes, fatty lesions (FL)) on MRI of the spine (MRI-spine) in patients (pts) with chronic back pain. Objectives To investigate the prevalence of structural lesions on MRI-spine in pts with chronic back pain. Methods Pts with back pain (≥3 months, ≤2 years, onset <45 years) recruited from 5 participating centres were included in the SPondyloArthritis Caught Early (SPACE)-cohort. Pts underwent MRI-spine scored independently by 3 blinded, well-calibrated readers for presence of ERO, FL and (bridging) syndesmophytes on T1-weighted images (STIR images viewed simultaneously). FL suggestive of spondylitis were scored when visible on ≥2 consecutive slices. For ERO or (bridging) syndesmophytes, suggestive of spondylitis, presence on ≥1 slice was sufficient. Agreement of 2/3 readers was used. Prevalence of structural lesions based on several cut-offs were calculated. Results All pts with complete MRI-spine data were included for analysis (n=306). Pts were grouped according to the ASAS axSpA criteria (radiographic, non-radiographic (imaging & clinical arm), no-axSpA and possible SpA (not fulfilling ASAS axSpA)). Prevalence of FL was the highest of all structural lesions in the spine in all subgroups. With a cut-off of ≥3 FL, the ‘false-positive’ rate in the no-axSpA group was low (6.5%) with still a considerable prevalence in the imaging and radiographic axSpA groups. Prevalence of ERO and (bridging) syndesmophytes was generally low (table;*‘weak’ SpA features (low LR) are: IBD, heel pain, dactylitis, IBP, good response to NSAIDs, peripheral arthritis, psoriasis, elevated ESR/CRP). Conclusions FL (≥3) on MRI-spine are primarily present in pts with MRI-SI positive non-radiographic and radiographic axSpA, not in no-axSpA and possible axSpA pts. ERO and (bridging) syndesmophytes in the spine are equally present in all groups. FL are the only type of structural lesions that can potentially discriminate between pts with and without axSpA. Disclosure of Interest None Declared