History of AS Classifications

Reviewed by: HU Medical Review Board | Last reviewed: March 2019 | Last updated: May 2019

Ankylosing spondylitis (AS) is an ancient condition. The Egyptian pharaoh Rameses II, of the book of Exodus, is thought to have had AS because his spine had fused and priests preparing him for mummification broke his neck to fit him into his coffin.

AS was first officially described in medical literature in the 19th century and called Von Bekhterev's disease or Marie-Strümpell disease. Then, in the 20th century, doctors renamed it rheumatoid spondylitis.1

With the widespread use of X-ray, spinal fusion became the hallmark used to diagnose a person with AS.

Diagnosis changes from traditional classes

However, beginning in the 1970s, doctors began to recognize that ankylosing spondylitis was one in a class of several subtypes of what they began calling spondyloarthritis. From the 1970s until the early 2000s, doctors began classifying spondyloarthritis into these groups:

  • Ankylosing spondylitis (AS)
  • Psoriatic arthritis
  • Reactive arthritis, which is associated with inflammatory bowel disease
  • Undifferentiated spondyloarthritis, which is spondyloarthritis that doesn’t seem to fit into any of the other subtypes.1,2

In 1984, researchers developed the New York criteria, which required sacroiliitis (severe inflammation and sacroiliac joint damage) be visible on X-ray. However, as MRIs came into greater use, doctors began to recognize that their patients could have back pain and other signs of AS long before sacroiliac joint damage appeared on X-rays.

Changes happening

This led to calls for classifications that recognized the early, more subtle or non-standard signs of AS.

In the late 1990s to early 2000s, with the advent of testing for the presence of the HLA-B27 genetic marker and the use of MRIs, a group of researchers from ASAS, the Assessment of SpondyloArthritis International Society, recommended the types of spondyloarthritis be refined to include these three classifications1-3:

  • Axial spondyloarthritis (AxSpA), for people who show inflammation and fusion of the sacroiliac joints on X-ray, along with limited back motion, and long-term back pain.
  • Peripheral spondyloarthritis, for those who have arthritis in their arms and legs, and several other signs of spondyloarthritis such as IBD, but not necessarily visible signs of sacroiliac inflammation on X-ray.
  • Non-radiographic axial spondyloarthritis, for those people who do not show inflammation or fusion on X-ray but may show changes of the sacroiliac joints on MRI, along with other classic symptoms such as elevated CRP, a history of uveitis, family history of AS, and other signs of inflammatory back pain.

Because these classifications are more sensitive and specific than earlier criteria, it allows doctors to diagnose patients earlier and more accurately.3

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