Calculators · Rheumatology · Score
ASDAS-CRP (Ankylosing Spondylitis Disease Activity Score)
Also called ASDAS, axial spondyloarthritis disease activity score
Axial spondyloarthritis disease activity from three BASDAI items, patient global and CRP (preferred ASDAS version).
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Formula and scoring
ASDAS-CRP = 0.12·back pain + 0.06·morning stiffness duration + 0.11·patient global + 0.07·peripheral pain/swelling + 0.58·ln(CRP mg/L + 1). CRP <2 mg/L is entered as 2.
Exam and ward pearls
- Cut-offs 1.3, 2.1 and 3.5 separate the four states; the 1.3–2.1 band was renamed "low" (from "moderate") in the 2018 ASAS update.
- A fall of ≥1.1 units is a clinically important improvement; a fall of ≥2.0 is a major improvement (Machado 2011).
When not to rely on it
- All four patient items are 0–10 numerical rating scales; the stiffness item rates duration, not severity.
Source
- Lukas C, Landewé R, Sieper J, et al. Development of an ASAS-endorsed disease activity score (ASDAS) in patients with ankylosing spondylitis. Ann Rheum Dis. 2009;68(1):18-24. doi:10.1136/ard.2008.094870 · PMID 18625618
- Machado P, Landewé R, Lie E, et al. Ankylosing Spondylitis Disease Activity Score (ASDAS): defining cut-off values for disease activity states and improvement scores. Ann Rheum Dis. 2011;70(1):47-53. doi:10.1136/ard.2010.138594 · PMID 21068095
- Machado PM, Landewé R, van der Heijde D. Ankylosing Spondylitis Disease Activity Score (ASDAS): 2018 update of the nomenclature for disease activity states. Ann Rheum Dis. 2018;77(10):1539-40. doi:10.1136/annrheumdis-2018-213184 · PMID 29453216
- Assessment of SpondyloArthritis international Society (ASAS). ASDAS calculator: formulae, CRP rule and disease activity states. Link
Formula and cut-offs checked against these sources on 8 Nov 2026. Educational tool for clinicians; it does not replace clinical judgement.