RA Disease Activity Measures Comparison — SCE Rheumatology MCQ
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Correct answer: A — DAS28 uses a weighted formula including an acute-phase reactant; SDAI is an arithmetic sum including CRP; CDAI omits laboratory markers; Boolean remission requires simultaneous component thresholds.
Explanation lettering: D = shown as A · A = shown as C · E = shown as D · C = shown as E
D is correct. DAS28 combines 28-joint tender and swollen counts, patient global assessment and either ESR or CRP using a weighted formula. SDAI is the arithmetic sum of TJC28, SJC28, patient and evaluator global assessments, and CRP in mg/dL; CDAI uses the same clinical variables but omits CRP, allowing immediate calculation. The four-variable ACR/EULAR Boolean2.0 remission definition requires TJC28 ≤1, SJC28 ≤1, CRP ≤1 mg/dL and patient global assessment ≤2/10 simultaneously. It is a remission definition, not a continuous index, so components cannot compensate for one another. A reverses the laboratory requirements, B reverses the mathematical structure, and C incorrectly describes Boolean remission. E is false because joint counts are central to all these approaches.
Reference: Janke K et al. A systematic comparison of different composite measures (DAS28, CDAI, SDAI, and Boolean approach) for determining treatment effects on low disease activity and remission in rheumatoid arthritis. BMC Rheumatology. 2022. https://pubmed.ncbi.nlm.nih.gov/36482451/