ASAS Axial Spondyloarthritis Classification
ASAS classification criteria for axial spondyloarthritis (Rudwaleit 2009) — entry = back pain >= 3 months with age at onset < 45 years, then either the imaging arm (sacroiliitis on imaging plus >= 1 SpA feature) or the clinical arm.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Back pain >= 3 months
- Yes
- Age at onset < 45 years
- Yes
- HLA-B27 positive
- Yes
- Inflammatory back pain
- Yes
- Psoriasis
- Yes
Result: MEETS the ASAS axial-SpA classification
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Entry
- Back pain >= 3 months AND age at onset < 45 years.
- Imaging arm
- Sacroiliitis on imaging (active MRI or definite radiographic, modified New York) PLUS >= 1 SpA feature.
- Clinical arm
- HLA-B27 positive PLUS >= 2 other SpA features (inflammatory back pain, arthritis, enthesitis, uveitis, dactylitis, psoriasis, Crohn's/colitis, NSAID response, family history, HLA-B27, elevated CRP).
- Scope
- Classifies for study enrollment (admits radiographic and non-radiographic axial SpA); not a diagnostic test.
What you enter
- Back pain >= 3 months (entry)
- Age at onset < 45 years (entry)
- Sacroiliitis on imaging (active MRI or definite radiographic, modified New York)
- Inflammatory back pain
- Arthritis
- Enthesitis (heel)
- Uveitis
- Dactylitis
The other 6 fields
- Psoriasis
- Crohn's / colitis
- Good response to NSAIDs
- Family history of SpA
- HLA-B27 positive
- Elevated CRP
How this is calculated
Rudwaleit M, van der Heijde D, Landewé R, et al. The development of ASAS classification criteria for axial spondyloarthritis (part II): validation and final selection. Ann Rheum Dis. 2009;68(6):777-783. Entry + imaging arm or clinical arm. A classification tool, not a diagnosis. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.