Ankylosing Spondylitis — SCE Rheumatology MCQ

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EasyMusculoskeletal ImagingAnkylosing SpondylitisSCE Rheumatology

A 30-year-old man has clinical features suggestive of axial spondyloarthritis. Plain pelvic radiographs do not show sacroiliitis meeting the modified New York criteria. Which imaging investigation is most appropriate next to detect active inflammatory sacroiliitis?

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Correct answer: D — Unenhanced MRI with T1 and STIR sequences

The correct answer is D. In suspected axial spondyloarthritis with non-diagnostic sacroiliac-joint radiographs, NICE recommends unenhanced MRI using an inflammatory back pain protocol. Fluid-sensitive imaging such as STIR detects subchondral bone-marrow oedema associated with active inflammation before radiographic structural sacroiliitis develops; T1-weighted imaging assesses structural lesions and important mimics. CT depicts erosions, sclerosis and ankylosis well but is less suitable for detecting early active inflammation and entails ionising radiation. NICE specifically advises against scintigraphy because of inadequate diagnostic performance. Conventional tomography and FDG PET-CT are not recommended routine investigations for this indication. MRI findings must still be interpreted in clinical context, and a negative MRI does not by itself exclude axial spondyloarthritis.

Reference: National Institute for Health and Care Excellence. Spondyloarthritis in over 16s: diagnosis and management (NG65), recommendations 1.2.6–1.2.10, 2017; reviewed 2025. https://www.nice.org.uk/guidance/ng65/chapter/Recommendations