Non-radiographic axial spondyloarthritis patients without initial evidence of inflammation may develop objective inflammation over time.

Objectives: In patients with active axial spondyloarthritis (axSpA), inflammation in the SIJ or spine on MRI, an elevated CRP level or both are considered useful objective assessments for disease activity and initiation of TNF antagonists. The aim of this post hoc analysis of the randomized, double-blind ABILITY-1 study (NCT00939003) was to assess changes in objective inflammation over time. Methods: Patients with non-radiographic axSpA (nr-axSpA) were randomized to receive adalimumab 40 mg every other week or placebo for 12 weeks in ABILITY-1. MRIs were performed at baseline and week 12; CRP was measured every 4 weeks. Results: Of 94 placebo-treated ABILITY-1 patients, 29 (30.9%) had a normal MRI of the SIJs and spine, 57 (60.6%) had normal CRP and 20 (21.3%) had a normal MRI of the SIJs and spine and a normal CRP at baseline. After 12 weeks of placebo, 9/29 (31.0%) patients subsequently developed inflammation on MRI, 14/57 (24.6%) patients developed elevated CRP and 10/20 (50.0%) patients developed a positive MRI and/or elevated CRP through week 12. Conclusions: Patients who have clinically active disease but who lack objective evidence of inflammation initially may benefit from subsequent retesting for inflammation to guide treatment.