MRI Definitions Proposed for Structural Joint Lesions in Axial Juvenile Spondyloarthritis

Data-driven definitions were proposed for active inflammatory and structural lesions on magnetic resonance imaging (MRI) in axial juvenile spondyloarthritis (JSpA), in a study published in Arthritis Care and Research (Hoboken).

In 2009, based on consensus methodology, the Assessment of Spondyloarthritis International Society (ASAS) established MRI definitions in adults with SpA.

In the current study, researchers sought to determine sacroiliac (SIJ) MRI cutoffs for active and structural lesions, to be incorporated as imaging domains in the classification criteria, of axial disease in patients with JSpA.

Six musculoskeletal imaging experts who were blinded to clinical details reviewed MRI scans from an international cross-section of patients with JSpA. The reviewers globally assessed the presence or absence of lesions characteristic of axial SpA and conducted SIJ quadrant- or joint-based scoring. The sensitivity and specificity of lesion cutoffs were calculated with the use of rater majority (≥4 of 6 the reviewers).

All participants who were enrolled in the study fulfilled the provisional Pediatric Rheumatology International Trials Organization criteria for enthesitis/spondylitis-related juvenile idiopathic arthritis or had received a diagnosis of JSpA from a rheumatologist between 2006 and 2021 from 6 institutions across Europe (ie, Istanbul, Turkey; Sankt Augustin, Germany) and the United States (Bethesda, Maryland; Birmingham, Alabama; Madison, Wisconsin; Philadelphia, Pennsylvania).

Imaging from a total of 243 participants (61% adolescent boys; median age, 14.9 years) showed available sequences for detailed MRI scoring. The MRI sequences were available for detailed scoring of active inflammation-only in 17 individuals; structural lesions-only in 4 individuals; and inflammation and structural lesions in 222 individuals.

The optimal cutoffs for defining lesions typical of axial disease in JSpA were as follows:

• Inflammatory lesion: bone marrow edema in at least 3 SIJ quadrants across all SIJ MRI slices (sensitivity, 98.6%; specificity, 96.5%).
• Structural lesion(s): erosion in at least 3 SIJ quadrants or sclerosis or fat lesion in at least 2 SIJ quadrants or backfillor ankylosis in at least 2 joint halves across all SIJ MRI slices (sensitivity, 98.6%; specificity, 95.5%).

Both the sensitivity and the specificity of the optimal cutoffs in the validation cohort were found to be excellent. 

One of the study limitations included the fact that there was imaging protocol variability, as the MRI scans were collected as part of routine clinical care and not according to a specified protocol. Further, the current analysis was essentially an imaging study, which used expert consensus imaging as the gold standard, with no direct correlation to clinical findings or outcomes taken into consideration.

According to the study authors, “These are the first quantitative imaging cut-offs developed for use in juvenile SpA and leverage a large international cohort of children with SpA evaluated for axial disease. These definitions have applicability for inclusion in classification criteria and selection of patients for clinical trials.”

Disclosure: Some of the study authors have declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 

Reference

Weiss PF, Brandon TG, Lambert RG, et al. Data-driven MRI definitions for active and structural sacroiliac joint lesions in juvenile spondyloarthritis typical of axial disease; a cross-sectional international study. Arthritis Care Res (Hoboken). Published online September 5, 2022. doi:10.1002/acr.25014