Limited added value of whole spine MRI in spondyloarthritis for disease activity assessment

To evaluate the added value of whole spine magnetic resonance imaging (MRI) for disease activity assessment in ankylosing spondylitis (AS) and psoriatic arthritis (PsA).

Spine and sacroiliac joint (SIJ) MRI scans requested by rheumatologists between 2012 and 2018 were screened retrospectively, and patients who had known diagnosis of AS or PsA were included, if the MRI was done for disease activity assessment. All MRI scans were reviewed by two experienced musculoskeletal radiologists independently, blinded to patients' diagnosis and to the other MRI. Comparisons were done for the presence of active and structural lesions. In addition, radiologists were asked to rate for "confidence level for active inflammation related to SpA." Analysis was done using the consensus scores.

Ninety patients with known diagnosis of AS (n = 55) or PsA (n = 35) were included. The frequency of active and structural lesions was not significantly different both in AS vs PsA, neither in the cervical/thoracic/lumbar spine or the SIJ. The percentage of people only with any inflammatory changes on the spine MRI without any inflammation in the SIJ MRI was 24% in AS and 23% in PsA. However, considering the confidence level of the radiologists on active inflammation, only one patient's spine MRI was scored as active, while SIJ MRI being negative for inflammation.

The spinal MRI had limited added value to the SIJ MRI in SpA, when performed to assess disease activity, limiting its value in routine practice unless clinically indicated. Key Points • Spine MRI adds limited value to SIJs in SpA, when performed for disease activity assessment. • SpA disease activity assessment may be restricted to sacroiliac joint MRI, unless clinically indicated.