DAS28 Calculation — SCE Rheumatology MCQ

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ModerateRheumatoid ArthritisDAS28 CalculationSCE Rheumatology

A 48-year-old woman with rheumatoid arthritis has a 28-joint tender joint count of 4, a 28-joint swollen joint count of 3, an ESR of 28 mm/hour and a patient global assessment of disease activity of 45 mm on a 0–100 mm visual analogue scale. Using DAS28-ESR = 0.56×√(TJC28) + 0.28×√(SJC28) + 0.70×ln(ESR) + 0.014×PtGA, where ln denotes the natural logarithm, what is her approximate DAS28-ESR?

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Correct answer: D — 4.6

The correct answer is D, approximately 4.6. The four contributions are 1.12 from the tender joint count, 0.49 from the swollen joint count, 2.33 from the logarithm of the ESR and 0.63 from the patient global assessment. Their sum is 4.57. This lies within the UK-defined moderate disease-activity interval of 3.2 to 5.1. A value near 3.9 results from omitting the patient-global component, while a value near 3.4 can result from omitting the tender-joint contribution. A result of 3.0 omits substantial joint-count contributions, and 5.2 overestimates one or more terms. The original keyed answer was numerically correct, but the item has been repaired because its categorical options had overlapping boundaries and included a non-standard “very high” DAS28 category.

Reference: BMJ Open, “Association between fat-to-muscle ratio and secondary osteoporosis in rheumatoid arthritis: a cross-sectional study at a tertiary hospital in China”, disease activity assessment methods, 2025. https://www.nice.org.uk/guidance/ng100/chapter/Recommendations