10.41. Disease Activity Score-28 (DAS28)


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Disease activity score for rheumatoid arthritis. The 28 refers to the number of joints in which disease activity is rated (bilaterally: shoulder, elbow, wrist, knee, 5 × MCP, 5 × PIP).

For each joint, “swollen?” and “tender?” are asked; there is a visual analogue rating scale (100 mm in length) for arthritis activity, plus an inflammatory marker. In the original DAS28 (sometimes termed the DAS28-ESR), this was ESR (erythrocyte sedimentation rate). An alternative is the CRP (C-reactive protein), in the DAS28-CRP.

  • t28 = number of tender joints, range [0, 28].

  • sw28 = number of swollen joints, range [0, 28].

  • The CRP units are mg/L and in the range [0, 300].

  • The ESR units are mm/hr and in the range [1, 300].

  • The VAS (visual analogue scale) units are mm, range [0, 100]. Low is inactive arthritis; high is extremely active arthritis.

DAS28 score = 0.56 × √(t28) + 0.28 × √(sw28) + 0.70 × ln(ESR) + 0.014 × VAS

DAS28-CRP score = 0.56 × √(t28) + 0.28 × √(sw28) + 0.36 × ln(CRP + 1) + 0.014 × VAS + 0.96.

These are the “4-variable” DAS scales (tenderness, swelling, inflammatory marker, VAS). There are different 3-variables scales too, without the VAS, not implemented here.

10.41.1. Intellectual property rights

10.41.2. History

10.41.3. Source