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SDAI Thresholds — SCE Rheumatology MCQ

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EasyRheumatoid ArthritisSDAI ThresholdsSCE Rheumatology

A 50-year-old man with rheumatoid arthritis has a Simplified Disease Activity Index (SDAI) of 4.0. Which set of SDAI thresholds correctly defines remission and low, moderate and high disease activity?

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

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Correct answer: A — Remission ≤3.3; low >3.3 to ≤11; moderate >11 to ≤26; high >26

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

The validated SDAI disease-activity states are remission ≤3.3, low disease activity >3.3 to ≤11, moderate disease activity >11 to ≤26, and high disease activity >26. Therefore, an SDAI of 4.0 represents low disease activity, just above the remission threshold. Option A gives commonly used DAS28 rather than SDAI boundaries, while option B corresponds broadly to CDAI categories. Options C and D use incorrect SDAI cut-offs. SDAI is calculated by summing the 28-joint tender and swollen joint counts, patient and physician global assessments, and C-reactive protein concentration; unlike DAS28, it does not require a weighted formula.

Reference: Aletaha D, Ward MM, Machold KP, et al. Remission and active disease in rheumatoid arthritis: defining criteria for disease activity states. Arthritis & Rheumatism. 2005;52:2625–2636. https://pubmed.ncbi.nlm.nih.gov/16142705/