ANA interpretation — SCE Rheumatology MCQ

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EasyMusculoskeletal InvestigationsANA interpretationSCE Rheumatology

A 26-year-old woman has photosensitive rash and inflammatory arthralgia. ANA is positive at 1:1280 homogeneous pattern. Anti-dsDNA is high and C3/C4 are low. Urine dipstick shows protein 2+ and blood 2+. What is the most likely diagnosis?

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Correct answer: C — Systemic lupus erythematosus with possible nephritis

Explanation lettering: B = shown as A · A = shown as B · D = shown as C · C = shown as D

Systemic lupus erythematosus with possible nephritis is best because high-titre ANA with anti-dsDNA, low complement and urinary abnormalities supports active SLE with renal involvement. A is less suitable because OA does not cause lupus serology or proteinuria; B is less suitable because mechanical back pain is unrelated; C is less suitable because incidental ANA would not explain low complement and urinary sediment; E is less suitable because gout causes crystal arthritis rather than immune nephritis. Clinical pearl: ANA is sensitive but becomes more meaningful when disease-specific antibodies and organ features align.

Reference: EULAR SLE recommendations 2023; BSR lupus guideline