Associations Between Clinical Characteristics and Magnetic Resonance Imaging of the Sacroiliac Joints and Spine: Exploratory Analysis of the Phase 4, Randomized, Placebo-Controlled STAR Study

Objective To compare demographic and clinical characteristics of patients who did and did not meet the magnetic resonance imaging (MRI) axial inflammation eligibility criteria for the STAR study. Methods STAR is a phase 4, randomized, placebo-controlled trial of guselkumab, a selective interleukin-23p19-subunit inhibitor, in participants with active PsA and MRI-confirmed axial inflammation. Axial involvement was defined as having a BASDAI score ≥4, spinal pain (BASDAI Question 2≥4, and MRI-confirmed axial inflammation (centrally read): Spondyloarthritis Research Consortium of Canada (SPARCC) score ≥3 for the sacroiliac joints (SIJ) or spine. Utilizing data from patients screened for STAR, this exploratory post hoc analysis compared demographic and disease characteristics for patients with both positive and both negative MRI scores (SIJ+/Spine+ vs SIJ−/Spine−). Results Among 487 screened patients in STAR, 433 had available MRI scores for both SIJ and Spine (SIJ+/Spine+: 65 [15%]; SIJ−/Spine−: 257 [59%]). The SIJ+/Spine+ subgroup had a higher mean CRP level (2.3 vs 1.4 mg/dL), higher mean spinal pain score (7.8 vs 7.3), and lower mean swollen (6.6 vs 8.1) and tender (11.1 vs 15.6) joint counts relative to the SIJ−/Spine− subgroup (all nominal P < 0.05). SIJ+/Spine+ patients were also significantly more likely to be male (Odds ratio [95% confidence intervals]: 3.96 [2.14, 7.34]) and numerically more likely to have a history of inflammatory back pain, while the presence of palmoplantar psoriasis was numerically less common than in SIJ−/Spine− patients. Conclusions Among patients with active PsA, male sex and higher CRP levels were significantly associated with MRI-confirmed SIJ and spinal inflammation. Registration ClinicalTrials.gov: NCT04929210.