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DAS28 Limitations in PsA — SCE Rheumatology MCQ

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ModerateSpondyloarthropathyDAS28 Limitations in PsASCE Rheumatology

A 38-year-old man with psoriatic arthritis has active synovitis of the right knee and left ankle, together with dactylitis of the left second toe. His DAS28-CRP is 3.0, indicating low disease activity by the DAS28 threshold. Which statement best describes the interpretation of this result?

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Correct answer: A — DAS28 may underestimate activity because the ankle and dactylitis are not captured; a PsA-specific assessment should be used

DAS28 may substantially underestimate this patient's PsA activity. Its 28-joint count includes the knee but excludes the ankle, feet and distal interphalangeal joints, and it does not directly assess dactylitis, enthesitis, psoriasis or axial disease. A low DAS28 therefore cannot establish low overall PsA activity when clinically active domains lie outside the score. A PsA-specific approach should be used: DAPSA assesses peripheral arthritis using broader joint counts, while MDA or PASDAS incorporate additional disease domains; separate domain assessment remains necessary. Option D is anatomically incorrect. Normal inflammatory markers would not correct the omitted domains, so B is false. DAS28 is neither expected to overestimate activity nor preferred specifically for oligoarticular PsA, excluding A and E.

Reference: Mulder MLM et al. Measuring disease activity in psoriatic arthritis: PASDAS implementation in a tightly monitored cohort reveals residual disease burden. Rheumatology. 2021;60:3165-3175. https://pubmed.ncbi.nlm.nih.gov/33331947/