Manouk de Hooge

Background: To compare the performances of magnetic resonance imaging (MRI) and radiography in detecting changes in structural lesions of the sacroiliac joints (SIJs) in routine care patients with axial spondyloarthritis (axSpA). Methods: SIJ MRIs and radiographs of routine care patients with axSpA in four European countries were collected as part of the EuroSpA Imaging Project. Patients were included if both MRIs and radiographs (≤ 6 months apart) were available at two time points (≥ 1 year apart). Images were evaluated centrally and independently by two trained readers (blinded to chronology and other imaging), applying the Spondyloarthritis Research Consortium of Canada SIJ scores (MRI) and the modified New York criteria (mNY, radiography). Intermodality agreement was assessed cross-sectionally and for change. Results: One-hundred-and-five patients (65 male, mean (SD) age 38.1 (10.9) years, symptom duration 9.1 (9.7) years), with a follow-up interval of 2.6 (1.4) years) were included. Baseline agreement between radiography and MRI was slight-to-fair for erosion detection (kappa = 0.12 to 0.42), poor to slight for sclerosis (− 0.04 to 0.07), and substantial to almost perfect for ankylosis (0.66–0.86). Agreement for change over time was poor-to-slight (− 0.04 to 0.20). While lesions remained largely stable on radiography (≤ 6 patients showing change in scores, per lesion type), MRI detected change in at least one lesion in ≥ 50% of patients (positive/negative change in scores (“progression”/”regression”): sclerosis 27/30, erosion 51/38, ankylosis 14/5). A composite MRI score of damage correlated well with mNY grades (Spearman rho = 0.65–0.69). Conclusions: Compared to radiography, MRI detected more SIJ structural lesion changes over time, reflecting its ability to capture dynamic changes not readily visible on radiography.

Psoriatic arthritis (PsA) is a heterogeneous inflammatory disease characterized by diverse musculoskeletal manifestations, including peripheral and axial arthritis, enthesitis, and dactylitis, often in conjunction with skin and nail psoriasis. Imaging modalities, particularly musculoskeletal ultrasound (MSUS) and magnetic resonance imaging (MRI), are crucial for accurate diagnosis, monitoring disease activity, and assessing structural damage in PsA. This review summarizes key insights from the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) 2025 session "Imaging in psoriatic arthritis: focus on axial MRI and peripheral musculoskeletal ultrasound," highlighting advancements in both peripheral and axial imaging. Efforts to standardize imaging protocols and scoring systems continue to enhance the utility and reliability of these tools in both research and daily practice, emphasizing the importance of nuanced interpretation to avoid common pitfalls. The session also underscored the valuable input from patient research partners, whose involvement highlights a crucial commitment to patient-centered research and care in rheumatology.

Objective: To evaluate the prevalence and anatomical distribution of inflammatory and structural MRI lesions in axial spondyloarthritis (axSpA) and compare these between patients with isolated axial involvement and those with peripheral manifestations. Methods: Data from the Assessment of SpondyloArthritis International Society (ASAS) Classification Cohort were analysed. Peripheral involvement was defined as past or current arthritis/dactylitis/enthesitis. Sacroiliac joint (SIJ) and spinal MRI lesions typical of axSpA were classified per ASAS lesion definitions and centrally read with multi-reader majority agreement (lesion present if called by the majority; SIJ ≥4/7, spine ≥5/9 readers). Comparisons between patients with and without peripheral manifestations were made. Results: Among 199 axSpA patients with SIJ MRI, 67 also had spinal MRI. Subchondral SIJ bone marrow oedema (BMO) was observed in 49%, without quadrant preference or subgroup differences. Other SIJ inflammatory lesions ranged from 4%–18%. Erosions (35%) and fat lesions (22%) were the most frequent structural lesions. In the spine, BMO, fat lesions and syndesmophytes/ankylosis were detected in 38%, 25% and 5%, respectively, with similar subgroup frequencies. Among 40 patients with both SIJ and whole spine MRI, inflammatory lesions were observed in both sites in 18%, SIJ only in 38%, and spine only in 20%. Structural lesions occurred in both sites in 19%, SIJ only in 30%, and spine only in 5%, with no subgroup differences. Conclusion: The prevalence and anatomical distribution of ASAS-defined MRI lesions was similar across axSpA subgroups. Notably, 20% exhibited spine-only inflammation, suggesting potential added diagnostic and monitoring value of spinal MRI, warranting further study.

Background: Cohort studies often use simple models, for example, completers-only or aggregated scores, to assess changes in imaging outcomes. With more data available, this introduces selection bias. Integrated analyses allow scores from multiple reading rounds; therefore, we assessed their effect on the change estimates’ precision compared with the completers-only analysis. Second, we compared change estimates from models using aggregated scores and scores analysed per reader. Methods: Patients with axial spondyloarthritis (axSpA) from the SPondyloArthritis Caught Early cohort were followed for 2 years. Imaging of the sacroiliac joints and spine was scored by ≥2 central readers in two rounds. Change in imaging outcomes was analysed using generalised estimating equations, with different patient and data selections for integrated and completers-only analyses. The integrated and multilevel completers-only analyses assessed outcomes per reader. Change estimates of the completers-only analysis of aggregated scores of readers were compared with estimates of the multilevel completers-only analysis. Results: The integrated analysis included 332 patients (vs 279 completers-only). Compared with the multilevel completers-only analysis, the integrated analysis included 12%–16% more patients with a similar precision. Within the completers-only population, change estimates from models using reader and aggregated scores were similar for continuous outcomes. However, similar comparisons in dichotomous outcomes showed that models with aggregated scores underestimated spinal changes (maximum 82% less) and overestimated sacroiliac joint changes (maximum 37% more). Conclusion: Multilevel models retain level variability by integrating information across patients, time points, readers and rounds to reduce selection bias and improve precision of change, which would otherwise be lost in simpler models.

Background: The Leiden group and the Assessment of Spondyloarthritis International Society (ASAS)-MRI study group have proposed definitions for structural (SL) and active (AL) lesions typical for axial spondyloarthritis (axSpA) on MRI of the sacroiliac joints (MRI-SIJ). Objectives: To analyse the predictive validity of proposed SL and AL MRI-SIJ definitions in early axSpA and compare proposed AL with the current ASAS-MRI-SIJ+ definition. Methods: Patients with chronic back pain (≤2 years) from the Spondyloarthritis Caught Early cohort were diagnosed as axSpA or non-axSpA after 2 years follow-up. Three central readers scored baseline MRI-SIJ for SL (erosions and fat lesions) and AL (bone marrow oedema). Validation required specificity and positive predictive value (PPV) ≥95%. Results: Among 643 patients (52% axSpA), SL were infrequent (2%–14%). All Leiden and most MRI study group SL definitions met the validation threshold, except for ‘erosion in ≥2 consecutive slices’ and the overall MRI study group definition (PPV <95%). The ASAS-MRI-SIJ+ definition had a higher sensitivity than the MRI study group AL (40% vs 31%) with similar specificity (98% vs 99%). Combining SL and AL, the Leiden SL with ASAS-MRI-SIJ+ definition met the validation threshold with the highest sensitivity (46%). SL increased sensitivity beyond AL alone by 6%–11%. Conclusions: The ASAS-MRI-SIJ+ definition outperforms the MRI study group AL. The Leiden SL combined with the ASAS-MRI-SIJ+ definition is validated, most sensitive and feasible as it simultaneously upholds lesion quantification and detection precision, making it the preferred approach. Nevertheless, SL were uncommon in early axSpA, contributing only marginally beyond AL definitions in early diagnosis.