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CDAI Definition — SCE Rheumatology MCQ

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EasyRheumatoid ArthritisCDAI DefinitionSCE Rheumatology

A 40-year-old woman with rheumatoid arthritis has her disease activity assessed using the Clinical Disease Activity Index (CDAI). Which statement correctly defines the CDAI and distinguishes it from the DAS28?

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

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Correct answer: D — It sums 28-joint tender and swollen joint counts, patient global assessment and evaluator global assessment, without an acute-phase reactant.

CDAI is calculated as TJC28 + SJC28 + patient global assessment + evaluator global assessment, with each global assessment scored from 0 to 10. It contains no ESR or CRP, so it can be calculated immediately from the clinical assessment. In contrast, DAS28 uses tender and swollen 28-joint counts, patient global assessment and an acute-phase reactant—either ESR or CRP—in a weighted formula; it does not include evaluator global assessment. Option A omits three CDAI components. Option B incorrectly adds ESR. Option E is wrong because CDAI and DAS28 have different components and calculation methods. Option C more closely describes the SDAI, which adds CRP to the clinical components. CDAI remission is defined as a score of 2.8 or below.

Reference: Aletaha D et al. Acute phase reactants add little to composite disease activity indices for rheumatoid arthritis: validation of a clinical activity score. Arthritis Research & Therapy. 2005. https://pubmed.ncbi.nlm.nih.gov/15987481/