Parameters:
(1) total 28 joint count for tenderness
(2) total 28 joint count for swelling
(3) C-reactive protein (CRP) in mg/L
(4) patient assessment of global health (GH) using a 100 mm VAS ranging from 0 (very good) to 100 (very poor)
28 joint counts:
(1) shoulders (2)
(2) elbows (2)
(3) wrists (2)
(4) MCP for 4 fingers (8)
(5) MCP thumb (2)
(6) PIP for 4 fingers and thumb (10)
(7) knees (2)
disease activity score using 4 variables =
= (0.56 * SQRT(28 joint tenderness count)) + (0.28 * SQRT(28 joint swelling count)) + (0.36 * LN(CRP + 1)) + (0.014 * (global health)) + 0.96
disease activity score using 3 variables =
= (1.1 * ((0.56 * SQRT(28 joint tenderness count)) + (0.28 * SQRT(28 joint swelling count)) + (0.36 * LN(CRP + 1)))) + 1.15
where:
• The addition of 1 in CRP + 1 prevents LN(0).
Interpretation:
• minimum score: 0.96 for the 4 variable version and 1.15 for the 3 variable version
• maximum score: around 8.5 for the 4 variable equation and around 7.9 for the 3 variable version
• The higher the DAS28 CRP the higher the disease activity.
