Background The imaging arm of the ASAS axial spondyloarthritis (SpA) criteria requires the presence of sacroiliitis on MRI or radiographs. In patients (pts) with non-radiographic axial SpA (nr-axSpA), there may be inflammation along the spine in the absence of sacroiliac joint (SIJ) inflammation on MRI.

Objectives To determine the concurrent existence of inflammation on MRI in the SIJ and the spine at baseline (BL) as assessed by the SPARCC scoring method in nr-axSpA pts.

Methods ABILITY-1 is an ongoing multicenter, randomized, controlled trial of adalimumab vs. placebo in pts with nr-axSpA (fulfilling ASAS axial SpA criteria but not modified New York criteria for AS) who had an inadequate response, intolerance, or contraindication to NSAIDs. MRI of the SIJ and spine were performed at BL and at week 12, and were centrally read using the SPARCC method (6DVU method for the spine) by 2 independent, blinded readers. Average scores of the readers were used. The proportion of pts with SPARCC score ≥2 for either the SIJ or spine was evaluated. For the purpose of these analyses, all pts were combined, independent of randomization.

Results Mean symptom duration of the study population (N=185) was 10 yrs. At BL, 48% of pts were reported by the local investigator to have past or present MRI evidence of sacroiliitis as required by the ASAS axial SpA criteria. Of pts with available BL SPARCC scores, 40% had a BL SIJ score ≥2 and 52% had a BL spine score ≥2. Of the pts with BL SPARCC SIJ score <2, 49% had evidence of spinal inflammation, with a BL SPARCC spine score ≥2. Figure 1 shows the cumulative probability plot of spine scores for pts with SIJ score <2 or ≥2. BL disease characteristics of pts with BL spine score <2 vs. ≥2 were generally comparable except for mean age (36 vs. 40 yrs) and SIJ scores (3.2 vs. 6.5); likewise for pts with BL SIJ score <2 vs. ≥2, except for gender (61% vs. 44% female).

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Conclusions Assessment by experienced readers shows that spinal inflammation on MRI may be observed in half of nr-axSpA pts without SIJ inflammation on MRI. MRI of both sites might be of value when evaluating for nr-axSpA. As pts in this study had long disease duration, these data need to be confirmed in pts with shorter disease duration.

Disclosure of Interest D. van der Heijde Consultant for: Abbott, Amgen, AstraZeneca, BMS, Centocor, Chugai, Eli-Lilly, GSK, Merck, Novartis, Otsuka, Pfizer, Roche, Sanofi-Aventis, Schering-Plough, UCB, Wyeth, J. Sieper Grant/Research support from: Abbott, Merck, Pfizer, UCB, Consultant for: Abbott, Merck, Pfizer, UCB, W. Maksymowych Grant/Research support from: Abbott, Consultant for: Abbott, M. Brown Consultant for: Abbott, S. Sarkar Shareholder of: Abbott, Employee of: Abbott, A. Pangan Shareholder of: Abbott, Employee of: Abbott