POS1010 SPINAL RADIOGRAPHIC PROGRESSION AND ITS ASSOCIATION WITH PROGRESSION TO ANKYLOSING SPONDYLITIS IN PATIENTS WITH NON-RADIOGRAPHIC AXIAL SPONDYLOARTHRITIS.

Abstract

BackgroundPrevention of structural damage of the axial skeleton is an important goal of treatment in axial spondyloarthritis (axSpA)1. Most studies concerning spinal radiographic progression focused on ankylosing spondylitis (AS). Data on spinal radiographic progression in patients with non-radiographic (nr)-axSpA is limited and data on the relation between spinal and sacroiliac radiographic progression in this population is lacking.ObjectivesTo assess long-term spinal radiographic progression in patients with nr-axSpA. Secondly, to explore the association between radiographic progression to AS and spinal radiographic progression in these patients.MethodsPatients enrolled in the ongoing Groningen Leeuwarden Axial SpA (GLAS) cohort, classified as nr-axSpA at baseline, with pelvic and spinal (lumbar and cervical) radiographs available at baseline and at least one follow-up visit at 2, 4 or 6 years were selected for analyses. Progression from nr-axSpA to AS was defined as progression to modified New York (mNY) sacroiliitis score ≥2 bilaterally or ≥3 unilaterally. Radiographs of nr-axSpA patients were randomized with radiographs of AS patients and scored in known time sequence by two trained readers blinded for patient characteristics. SK and RW scored the SI joints and in case of disagreement in axSpA classification, the score of a third independent reader (AS) was used. SK and MS scored the spinal radiographs according to the modified stoke ankylosing spondylitis spinal score (mSASSS; 0-72), and the mean of both total scores was calculated. In case of >5 points discrepancy between both readers, the mSASSS of a third independent reader (FM) together with the closest of the scores of the primary readers was used. The mSASSS change of nr-axSpA patients who did en did not progress to AS was compared with Mann-Whitney U tests.ResultsIncluded were 60 patients with a clinical diagnosis of nr-axSpA, confirmed by their sacroiliac radiographic score at baseline. Mean age was 37±10 years, 53% were male, median symptom duration was 9 (IQR 2-17) years, 75% were HLA-B27+, and mean ASDAS was 2.6±1.1.In total 15 patients progressed to AS. Median mSASSS at baseline was 1.5 (IQR 0.5 – 4.4). Median change in mSASSS from baseline was 0.0 (IQR 0.0 – 1.0) vs. 1.0 (IQR 0.0 – 1.5) at 2 years; 1.2 (IQR 0.3 – 3.5) vs. 2.0 (0.5 – 2.7) at 4 years; and 1.8 (1.0 – 3.8) vs. 2.5 (0.5 – 3.5) at 6 years for non-AS progressors and AS progressors, respectively (Figure 1). These mSASSS changes weres were not significantly different at any timepoint (p = 0.456, p=0.814, p=0.929 for 2-, 4-, and 6-year follow-up, respectively).Figure 1.Comparison of mSASSS progression between patients with and without progression to AS during the first 6 years of follow-up.ConclusionIn our observational cohort of patients with nr-axSpA with up to 6 years of follow-up, mSASSS progression was low (< 1 mSASSS unit/year) and was not different between patients who did and did not progress to AS.