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What Is Axial Spondyloarthritis

By Spondylitis Association of America

What Is Axial Spondyloarthritis
This article originally appeared in the Spring 2013 issue of Spondylitis Plus, the quarterly news magazine of Spondylitis Association of America. Members receive every copy of Spondylitis Plus in the mail for free.

A relatively new term has been seen more and more in medical literature over the past few years: Axial spondyloarthritis (AxSpA). This specific classification of spondyloarthritis was originally developed by the Assessment of Spondyloarthritis international Society (ASAS).

Dr. Jim Rosenbaum, Division Chief of Arthritis and Rheumatic Diseases at the Oregon Health & Science University, and past chair of SAA's Medical and Scientific Advisory Board, describes AxSpA thusly:

"Once upon a time, we refused to diagnose ankylosing spondylitis unless the x-rays of the sacroiliac joints were abnormal.

The problem is that the disease can be mild or it can take years before the x-rays show changes. And even when the x-rays are abnormal, interpretation is always subject to some debate.

So the ASAS group in Europe has appropriately tried to define new criteria for the diagnosis such that x-ray changes are not required and that group preferred a new name: axial spondyloarthritis."

A study published in May 2012 in Arthritis Care & Research regarding the prevalence of AxSpA described this classification as "a form of spondyloarthritis in which the predominant symptom is back pain, and where radiographic sacroiliitis might or might not be present. If definite radiographic sacroiliitis on plain X-rays is present, the disease can be classified as ankylosing spondylitis (AS).”

The study, "Prevalence of axial spondyloarthritis in the United States: Estimates from a cross-sectional survey," found that as much as 1% of the adult United States population may have axial spondyloarthritis. This means that as many as 2.7 million adults may be affected by the disease if the classification of axial spondyloarthritis is used. However, the study authors note that "current U.S. SpA prevalence estimates may be lower than the true value" because of the way the data was collected. Thus, even more may be affected than is estimated in the study.

The new classification can also affect how spondyloarthritis is diagnosed in terms of gender. In the Spring 2013 issue of Spondylitis Plus, Dr. Jessica Walsh wrote that, "When broader definitions are used to identify people with spondyloarthritis in the pelvis and/or spine (axial spondyloarthritis), the prevalence is similar in men and women."

In our Summer 2013 issue of Spondylitis Plus, Dr. John Reveille, Professor of Internal Medicine, Director of The Division Of Rheumatology and Clinical Immunogenetics at the University of Texas Medical School at Houston and member of SAA’s Board of Directors, argued that the axial spondyloarthritis classification is one of the ten most important questions facing the "Spondyloarthritis Community."

In regards to AxSpA, Dr. Reveille wrote:

"It takes up to 10 years between the time that the back pain begins and the x-rays turn positive for sacroiliitis, the hallmark of AS. This condition has been called 'pre-radiographic' axial spondyloarthritis. More recently, as groups of patients from Europe have been followed, it has become evident that many never go on to develop radiographic sacroiliitis, yet have other classical spondyloarthritis features (inflammatory back pain, positive MRIs for inflammation around the sacroiliac joints, HLA-B27 positivity, enthesitis, uveitis, positive family history, etc). This condition is called axial spondyloarthritis (AxSpA), and many consider AS to be part of this disease spectrum. Women with normal inflammatory blood markers who have AxSpA are more likely NOT to progress to AS. This has led to the development of criteria for axial spondyloarthritis as a disease entity, although the accuracy of these criteria as applied by doctors to patients in the general population is still being debated."

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