Axial Spondyloarthritis Classification: Assessing Need for Spine MRI

Results from a study showing infrequent inflammatory lesions of the spine in patients with chronic back pain with no sacroiliitis prompted researchers to recommended against including magnetic resonance imaging (MRI) in the Assessment of Spondyloarthritis International Society (ASAS) classification criteria for axial spondyloarthritis; this study was recently published in the Annals of the Rheumatic Diseases.¹

“In this early disease stage, the addition of a positive MRI-spine as [an] imaging criterion to the ASAS classification criteria for axSpA [axial spondyloarthritis] yielded a very low number of newly classified patients in both cohorts. Therefore, the use of MRI-spine is not recommended in the classification of patients with CBP [chronic back pain] suspected of axSpA,” Ms Zineb Ez-Zaitouni, from the department of rheumatology at Leiden University Medical Center in The Netherlands, and colleagues wrote in their study.

Ms Ez-Zaitouni and colleagues identified 541 patients in the SPondyloArthritis Caught Early (SPACE) cohort and 650 patients from the DEvenir des Spondylarthropathies Indifférenciées Récentes (DESIR) cohort with CBP for ≤3 years who underwent baseline imaging of sacroiliac joints (X-SI), MRI of sacroiliac joints (MRI-SI), and MRI for inflammatory lesions of the spine (MRI-spine). The imaging tests were scored by a minimum of 2 readers who looked for ≥5 bone marrow edemas (BMEs) per slice to determine the presence of axSpA.

“In the SPACE cohort, a positive MRI-spine was defined by the presence of ≥5 corner BME lesions highly suggestive of axSpA each visible on ≥2 consecutive slices and if ≥2 readers agreed,” Ms Ez-Zaitouni and colleagues wrote. “A positive MRI-spine was also defined by the ASAS consensus definition (≥3corner BME lesions on ≥2 consecutive slices) and if ≥2 readers agreed.”

Readers identified sacroiliitis at baseline in 40 patients (7%) and during MRI in 76 patients (14%) in the SPACE cohort, while there were 134 patients (21%) with sacroiliitis at baseline and 231 patients (36%) in the DESIR cohort. MRI-spine was positive in 4 patients (1%) in the SPACE cohort and 48 patients (7%) in the DESIR cohort. However, researchers noted 3 patients (1%) in the SPACE cohort and 8 patients (2%) in the DESIR cohort with a positive MRI-spine had no sacroiliitis on imaging.

Summary and Clinical Applicability

“Considering the number of MRI-spine [scans] needed to additionally classify a few patients, the longer scanning time for the patient and higher costs, we conclude that the yield of adding MRI-spine to the ASAS-criteria is unacceptably low in relation to the number of MRI-spine [scans] needed to be performed in patients with early disease,” Ms Ez-Zaitouni and colleagues wrote in their study.

Limitations

The researchers noted short symptom duration and extrapolation of data to the patient group as limitations in this study.

Reference

Ez-Zaitouni Z, Bakker PAC, van Lunteren M, et al. The yield of a positive MRI of the spine as imaging criterion in the ASAS classification criteria for axial spondyloarthritis: results from the SPACE and DESIR cohorts [published online June 29, 2017]. Ann Rheum Dis. doi:10.1136/annrheumdis-2017-211486