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Suspected non-radiographic axial spondyloarthritis — SCE Rheumatology MCQ

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ModerateMusculoskeletal InvestigationsSuspected non-radiographic axial spondyloarthritisSCE Rheumatology

A 32-year-old woman is assessed for 18 months of low back and alternating buttock pain. The pain wakes her during the second half of the night, improves with exercise and responds rapidly to naproxen. She has scalp psoriasis and previously had acute anterior uveitis. Examination shows restricted lumbar flexion but no neurological deficit. HLA-B27 is positive; CRP and ESR are normal. Plain radiographs of the sacroiliac joints do not show sacroiliitis meeting modified New York criteria. A previous routine lumbar MRI showed mild L5/S1 disc degeneration but did not adequately include the sacroiliac joints. Which imaging investigation is most appropriate now?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: C — Unenhanced T1-weighted and STIR MRI of the whole spine and sacroiliac joints

Explanation lettering: E = shown as A · A = shown as D · D = shown as E

Her age at onset, inflammatory back-pain phenotype, psoriasis, previous uveitis and HLA-B27 positivity create a high pre-test probability of axial spondyloarthritis. Normal inflammatory markers and radiographs do not exclude the diagnosis. NICE recommends that when sacroiliac radiographs do not meet modified New York criteria, the next investigation is an unenhanced MRI using an inflammatory back-pain protocol: sagittal T1-weighted and STIR sequences of the whole spine, together with coronal-oblique T1-weighted and STIR imaging of the sacroiliac joints. A is not the recommended next test: CT depicts structural erosions and sclerosis well but exposes the patient to ionising radiation and is less appropriate for detecting active inflammation. B is attractive because the sacroiliac joints are the principal diagnostic site, but it omits the whole-spine sequences specified by the NICE protocol. D is unnecessary because gadolinium enhancement is not required for standard assessment of inflammatory lesions in suspected axial spondyloarthritis; it would be more relevant if infection or neoplasia were suspected. E is incorrect because scintigraphy lacks adequate diagnostic performance for axial spondyloarthritis and NICE specifically advises against offering it in this setting. The incidental mild disc degeneration does not explain the complete inflammatory and extra-articular phenotype.

Reference: Spondyloarthritis in over 16s: diagnosis and management — Recommendations (Last updated 2 June 2017) — https://www.nice.org.uk/guidance/NG65/chapter/Recommendations NICE Quality Standard QS170, Quality statement 2: Diagnosis of axial spondyloarthritis using imaging (28 June 2018) — https://www.nice.org.uk/guidance/qs170/chapter/quality-statement-2-diagnosis-of-axial-spondyloarthritis-using-imaging