Chapter 163: The Spondyloarthritides


The spondyloarthritides (SpA) are a family of diseases that include ankylosing spondylitis (AS), reactive arthritis (ReA), psoriatic arthritis (PsA), enteropathic arthritis, juvenile-onset SpA, and undifferentiated SpA. More recently, these disorders have been broadly classified as predominantly axial SpA, affecting the spine, pelvis, and thoracic cage, or predominantly peripheral SpA, affecting the extremities. Classification criteria based on these main clinical features have been developed that aide in early identification (Tables 163-1 and 163-2).

TABLE 163-1: ASAS Criteria for Classification of Axial Spondyloarthritis (To Be Applied for Pts with Back Pain ≥3 Months and Age of Onset <45 Years)a

Sacroiliitis on imaging

  • Active (acute) inflammation on MRI highly suggestive of SpA-associated sacroiliitisb and/or
  • Definite radiographic sacroiliitis according to modified New York criteriac

SpA features

  • Inflammatory back paind
  • Arthritise
  • Enthesitis (heel)f
  • Anterior uveitisg
  • Dactylitise
  • Psoriasise
  • Crohn’s disease or ulcerative colitise
  • Good response to NSAIDsh
  • Family history of SpAi
  • HLA-B27
  • Elevated CRPj
aSensitivity 83%, specificity 84%. The imaging arm (sacroiliitis) alone has a sensitivity of 66% and a specificity of 97%.
bBone marrow edema and/or osteitis on short tau inversion recovery (STIR) or gadolinium-enhanced T1 image.
cBilateral grade ≥2 or unilateral grade 3 or 4.
dSee text for criteria.
ePast or present, diagnosed by a physician.
fPast or present pain or tenderness on examination at calcaneus insertion of Achilles tendon or plantar fascia.
gPast or present, confirmed by an ophthalmologist.
hSubstantial relief of back pain at 24–48 h after a full dose of NSAID.
iFirst- or second-degree relatives with ankylosing spondylitis (AS), psoriasis, uveitis, reactive arthritis (ReA), or inflammatory bowel disease (IBD).
jAfter exclusion of other causes of elevated CRP.
Abbreviations: ASAS, Assessment of Spondyloarthritis International Society; CRP, C-reactive protein; MRI, magnetic resonance imaging; NSAIDs, nonsteroidal anti-inflammatory drugs; SpA, spondyloarthritis.
Source: Rudwaleit M et al: The development of assessment of spondyloarthritis international society classification criteria for axial spondyloarthritis (part II). Ann Rheum Dis 68:777, 2009. Adapted by permission from BMJ Publishing Group Limited.
TABLE 163-2: ASAS Criteria for Peripheral Spondyloarthritisa
Arthritisb Or Enthesitis Or Dactylitis


One or more of the following SpA features:

  • Psoriasis
  • Crohn’s disease or ulcerative colitis
  • Preceding infection
  • Uveitis
  • HLA-B27
  • Sacroiliitis on imaging (radiographs or MRI)

OR two or more of the following SpA features:

  • Arthritis
  • Enthesitis
  • Dactylitis
  • Inflammatory back pain ever
  • Family history for SpA
aSensitivity 78%, specificity 82%.
bPeripheral arthritis, usually predominantly lower limb and/or asymmetric. The various SpA features are as defined in Table 163-1. Preceding infection refers to preceding gastrointestinal or urogenital infection.
Source: Rudawaleit M et al: The assessment of spondyloarthritis international society classification criteria for peripheral spondyloarthritis and for spondyloarthritis in general. Ann Rheum Dis 70:25, 2011. Adapted by permission from BMJ Publishing Group Limited.

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