Objective: (1)

To compare the capacity to detect sacroiliac joint (SIJ) erosions and baseline-to-week 104 change in erosions between magnetic resonance imaging (MRI) and radiographs in recent-onset axial spondyloarthritis (axSpA); and (2) to compare treatment-discriminatory capacities of MRI and radiographic scores for erosion detection in patients receiving etanercept in the Effect of Etanercept on Symptoms and Objective Inflammation in Nonradiographic axSpA (EMBARK) trial vs controls in the DESIR (Devenir des Spondylarthropathies Indifférenciées Récentes) cohort.

Methods:

Anonymized SIJ MRI and radiographs were assessed at patient and joint surface levels. Three readers evaluated MRI; 3 different readers evaluated radiographs. Final scores for comparison of radiographs and MRI for detection of erosions were assigned based on agreement of ≥ 2 of 3 readers’ assessments.

Results:

At baseline, discordance in erosion detection between imaging methods was more frequent for MRI erosions in the absence of radiographic erosions (48/224 [21.4%] patients) than for radiographic erosions in the absence of MRI erosions (14/224 [6.3%] patients; P < 0.001). After 104 weeks, a decrease in erosions was observed on MRI but not radiographs in 49/221 (22.2%) patients, and on radiographs but not MRI in 6/221 (2.7%) patients (P < 0.001). In the treatment-discriminant capacity analysis, the largest standardized differences between etanercept and control cohorts at week 104 were changes in Spondyloarthritis Research Consortium of Canada MRI erosion discrete score, changes in erosion average score, and meeting the modified New York criteria on radiographs, with unadjusted/adjusted Hedges G effect sizes of 0.40/0.50, 0.40/0.56, and 0.40/0.43, respectively.

Conclusion:

In recent-onset axSpA, SIJ erosions and erosion change were observed more frequently on MRI than radiography. The significance of interval improvement of MRI erosions warrants further research. [ClinicalTrials.gov: NCT01258738, NCT01648907].