An Historical Perspective
In this video from MD Magazine, Dr. Philip J. Mease, MD –– a respected leader in the field –– explains the most recent classification guidelines released by the Assessment of SpondyloArthritis international Society (ASAS).
Historically, spondyloarthritis has been characterized into a number of different subtypes, including ankylosing spondylitis (“AS”), psoriatic arthritis, the arthritis associated with inflammatory bowel disease—something called reactive arthritis, which is triggered by an infectious agent. And then we have had a broad category called undifferentiated spondyloarthritis, where we put had put a patient historically who we really thought had spondyloarthritis but didn’t fit into any of the other subtypes…
The newest classification criteria for spondyloarthritis has been established by the ASUS group, which is an international spondyloarthritis research group. And they have suggested that it’s best to classify patients as either having axial spondyloarthritis or peripheral spondyloarthritis.
The axial spondyloarthritis is divided into patients who have characteristic radiographic changes of the sacroiliac joints consistent with AS. And that would be your classic AS person who fulfills the old New York modified criteria, which includes limitation of back motion, back pain, and then these radiographic features of sacroiliitis.
There’s also an entity we are now using, the term “non-radiographic axial spondyloarthritis,” but we feel that that is going to be gradually changing and will have the general spectrum of axial spondyloarthritis either with or without radiographic changes in the sacroiliac (“SI”) joints. And in the latter group, some of the objective features may include MRI changes of the SI joint, or elevated CRP and also other features that are consistent with spondyloarthritis, such as a history of uveitis, family history of ankylosing spondylitis, inflammatory back pain features, and so on.
The other way in which the axial group is being classified is by having a positive HLA-B27, which is a genetic test, and then having at least two features that are consistent with a clinical diagnosis of spondyloarthritis. So, that’s on the spondyloarthritis side.
On the peripheral spondyloarthritis side, these are patients who have arthritis, enthesitis, for example, and then have several clinical features of spondyloarthritis. And this could include patients, for example, with inflammatory bowel disease–associated spondyloarthritis who commonly present with more peripheral joint and enthesitis findings as opposed to axial findings.
This is now the more current classification criteria. I suspect that as time goes by, we’ll see further refinement and evolution of these classification criteria, especially as we become more sophisticated about our understanding of genetics, and how to profile people genetically or with other biomarkers. So, this will aid us in time.