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Ankylosing Spondylitis

General Information


  • chronic inflammatory rheumatic disease primarily involving the sacroiliac joints and spine1,2
  • a subtype of a group of inflammatory disorders called axial spondyloarthritis2,3

Also called

  • AS
  • Bechterew disease
  • Marie-Strumpell disease


  • spondyloarthropathies
  • axial spondyloarthritis
    • spondyloarthritis with axial disease, regardless of structural damage (21684383Lancet 2011 Jun 18;377(9783):2127)
    • characterized by changes in sacroiliac joints and spinal structures
      • inflammatory changes may include sacroiliitis, spondylitis, spondyloarthritis, and spondylodiscitis
      • osteoproliferative changes may include syndesmophytes and vertical column ankylosis
      • Reference - 21339229Ann Rheum Dis 2011 Mar;70 Suppl 1:i97
    • subtypes include
    • diagnostic classification criteria for axial spondyloarthritis, developed by Assessment of SpondyloArthritis international Society (ASAS)
      • valid for patients with back pain ≥ 3 months and age of onset < 45 years
      • patients must have either of
        • sacroiliitis on x-ray (grade 2 bilateral or grade 3-4 unilateral) or magnetic resonance imaging (bone marrow edema or osteitis) plus ≥ 1 spondyloarthritis feature below
        • HLA-B27 plus ≥ 2 other spondyloarthritis features below
      • spondyloarthritis features
        • inflammatory back pain
        • arthritis
        • enthesitis
        • uveitis
        • dactylitis
        • Crohn disease/ulcerative colitis
        • psoriasis
        • family history of spondyloarthritis
        • good response to nonsteroidal anti-inflammatory drugs (NSAIDs)
        • HLA-B27
        • elevated C-reactive protein or erythrocyte sedimentation rate
      • Reference - 19297344Ann Rheum Dis 2009 Jun;68(6):777, editorial can be found in 19435721Ann Rheum Dis 2009 Jun;68(6):765
  • ankylosing spondylitis
    • type of axial spondyloarthritis with definite radiographic sacroiliitis (19297344Ann Rheum Dis 2009 Jun;68(6):777)
    • modified New York criteria for ankylosing spondylitis1,2
      • diagnosis of definite ankylosing spondylitis requires ≥ 1 clinical criteria plus 1 radiologic criterion
      • clinical criteria
        • low back pain for ≥ 3 months with inflammatory characteristics (such as, improves with exercise, does not improve with rest)
        • limited lumbar spine motion in sagittal and frontal planes
        • decreased chest expansion for age and sex
      • radiologic criteria (on x-ray)
        • bilateral sacroiliitis ≥ grade 2
        • unilateral sacroiliitis ≥ grade 3
    • guidelines for early identification of ankylosing spondylitis from the Australian 3E initiative in rheumatology
      • consider ankylosing spondylitis if
        • inflammatory back pain in patients < 45 years old
        • patient responds to appropriate course of NSAIDs
        • elevated inflammatory markers (erythrocyte sedimentation rate or C-reactive protein) present, although absence does not rule out ankylosing spondylitis
      • radiologic evaluation
        • plain spinal and pelvic x-rays are appropriate initial imaging techniques
        • magnetic resonance imaging is useful in detecting early changes
      • refer patients with inflammatory back pain to a rheumatologist for further evaluation
      • Reference - 18279132Med J Aust 2008 Feb 18;188(4):235
  • outcome measures for evaluating disease activity 4
    • Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) measures overall level of severity of symptoms over past week
      • score each of below on visual analog scale of 0-10, with 10 being very severe
        • fatigue
        • pain in hips, back, and neck
        • pain in joints other than hips, back, or neck
        • discomfort in areas tender to touch or pressure
      • take sum of numbers above, then add mean of
        • intensity of morning stiffness (scored 0-10 on visual analog scale)
        • duration of morning stiffness from 0 hours to 2 or more hours (scored on 0-10 scale)
      • to get final score, divide total sum by 5
    • Bath Ankylosing Spondylitis Functional Index (BASFI) measures severity of functional abilities
      • score each of below as "easy" to "impossible" on visual analog scale of 0-10
        • putting on socks unaided
        • picking up pen from floor
        • reaching high shelf unaided
        • getting up from armless chair
        • getting off floor from back
        • standing unaided for ≥ 10 minutes
        • climbing 12-15 stairs unaided
        • looking over shoulder
        • performing demanding activity
        • performing full day's activity
      • total score from all 10 items and divide by 10 for final score
      • scored as a continuous outcome and reported as score at follow-up or change in score from baseline
    • ASAS response criteria combines measures of symptoms and disability
      • ASAS partial remission criteria requires score ≤ 2 units (on 0-10 scale) in 4 disease measures
        • spinal inflammation (composite of intensity and duration of morning stiffness, measured by BASDAI)
        • spinal pain (combination of total back pain and nocturnal back pain over past week, measured on numerical scale 0-10 or visual analog scale 0-100)
        • patient global assessment of spondylitis over past week (measured on numerical scale 0-10 or visual analog scale 0-100)
        • functional impairment as measured by BASFI
      • ASAS20 improvement criteria requires
        • improvement of ≥ 20% and ≥ 1 unit (on 0-10 scale) in ≥ 3 of disease measures above
        • no worsening of ≥ 20% and ≥ 1 unit (on 0-10 scale) in remaining unimproved measure
      • ASAS40 improvement criteria requires
        • improvement of ≥ 40% and ≥ 2 units (on 0-10 scale) in ≥ 3 of disease measures above
        • no worsening at all in remaining measure
      • scored as binary outcome and reported as number or proportion of patients achieving improvement
    • Ankylosing Spondylitis Disease Activity Score (ASDAS) - measures severity of symptoms and signs of inflammatory reaction including
      • back pain (from BASDAI)
      • patient global assessment of spondylitis
      • peripheral pain and swelling (from BASDAI)
      • duration of morning stiffness (from BASDAI)
      • C-reactive protein or erythrocyte sedimentation rate


General references used

  1. McVeigh CM, Cairns AP. Diagnosis and management of ankylosing spondylitis. BMJ. 2006 Sep 16;333(7568):581-5full-text
  2. Sieper J, Poddubnyy D. Axial spondyloarthritis. Lancet. 2017 Jul 1;390(10089):73-84
  3. van der Heijde D, Ramiro S, Landewé R, et al. 2016 update of the ASAS-EULAR management recommendations for axial spondyloarthritis. Ann Rheum Dis. 2017 Jun;76(6):978-991
  4. Sieper J, Rudwaleit M, Baraliakos X, et al. The Assessment of SpondyloArthritis international Society (ASAS) handbook: a guide to assess spondyloarthritis. Ann Rheum Dis. 2009 Jun;68 Suppl 2:ii1-44

Recommendation grading systems used

  • Assessment of SpondyloArthritis international Society/European League Against Rheumatism (ASAS/EULAR) grading system for recommendations
    • strength of recommendations
      • Grade A - consistent level 1 evidence
      • Grade B - consistent level 2 or 3 evidence or extrapolated recommendations from level 1 evidence
      • Grade C - level 4 evidence or extrapolated recommendations from category 2 or 3 evidence
      • Grade D - level 5 evidence or troublingly inconsistent or inconclusive studies of any level
    • levels of evidence
      • Level 1A - meta-analysis of randomized controlled trials
      • Level 1B - ≥ 1 randomized controlled trial
      • Level 2A - ≥ 1 controlled study without randomization
      • Level 2B - ≥ 1 type of quasi-experimental study
      • Level 3 - descriptive studies, such as comparative studies, correlation studies, or case-control studies
      • Level 4 - expert committee reports or opinions and/or clinical experience of respected authorities
      • Level 5 - expert opinion without explicit critical appraisal, or based on physiology, bench research or “first principles”
  • American College of Radiology (ACR) grading scale for recommendations
    • Rating 1, 2, and 3 - usually not appropriate
    • Rating 4, 5, and 6 - may be appropriate
    • Rating 7, 8, and 9 - usually appropriate
    • Reference - ACR Appropriateness Criteria for chronic back pain: suspected sacroiliitis/spondyloarthropathy (ACR 2016 PDF)

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Special acknowledgements

Choosing Wisely Canada acknowledges dissemination of their recommendations through DynaMed Plus to reach the point of clinical decision-making.
On behalf of the American College of Physicians
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How to cite

National Library of Medicine, or "Vancouver style" (International Committee of Medical Journal Editors):

  • DynaMed [Internet]. Ipswich (MA): EBSCO Information Services. 1995 - . Record No. T143424, Ankylosing Spondylitis; [updated 2018 Nov 30, cited place cited date here]. Available from Registration and login required.

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