ASDAS-CRP (Ankylosing Spondylitis Disease Activity Score)

The Ankylosing Spondylitis Disease Activity Score (ASDAS) is an index to assess disease activity in Ankylosing Spondylitis (AS).

The prefered score uses CRP, rather than ESR.

ASDAS-CRP = 0.12 x Back Pain + 0.06 x Duration of Morning Stiffness + 0.11 x Patient Global + 0.07 x Peripheral Pain/Swelling + 0.58 x Ln(CRP+1)

ASDAS-ESR = 0.08 x Back Pain + 0.07 x Duration of Morning Stiffness + 0.11 x Patient Global + 0.09 x Peripheral Pain/Swelling + 0.29 x √(ESR)

Back pain, patient global assessment, duration of morning stiffness and peripheral pain/swelling are all assessed on a numerical rating scale (from 0 to 10).

The 3 cut-offs selected to separate these states (figure 1) were: <1.3 between "inactive disease" and "moderate disease activity", <2.1 between "moderate disease activity" and "high disease activity", and >3.5 between "high disease activity" and "very high disease activity".

Cut-offs for improvement scores were: a change ≥1.1 units for "clinically important improvement" and a change ≥2.0 units for "major improvement".