Classification of Spondyloarthritis: An Historical Perspective
MAY 24, 2016
MD Magazine Staff
John D. Reveille, MD, and Philip J. Mease, MD, provide insight on the evolution in classifying spondyloarthritis, including a review of the criteria.
John D. Reveille, MD: Ankylosing spondylitis (AS) has been around for a long time. The mummy of Rameses II, who was the Rameses of the book of Exodus, actually had AS. They had to break his neck, because his spine was fused in a forward position, to fit him into the sarcophagus. It’s been around a long time. A lot of skeletons of old have been found to have AS. A lot of historical figures have had AS, the most recent being Pope John Paul II. That’s why you saw him completely hunched over later in his life. But the disease really was first described in the 19th century. It was called Von Bekhterev's disease, or Marie-Strümpell disease, and then in the 20th century they were calling it rheumatoid spondylitis. It was only with discovery of the blood test to diagnose rheumatoid arthritis, like the rheumatoid factor, and then the discovery of the HLA-B27. But really, the realization was these were very, very different diseases.
Philip J. Mease, MD: Historically, spondyloarthritis has been characterized into a number of different subtypes, including ankylosing spondylitis, 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.
So, now there has been an evolution in the classification criteria. First, there was the Caspar Criteria for psoriatic arthritis that was published in 2006. And the Caspar Criteria is based on a clinician evaluating a patient, determining that they have inflammatory arthritis, enthesitis, or spondylitis. And then if they have three points from a list of elements, then they may be classified as having psoriatic arthritis. If the person has current psoriasis, that gets them two points. If they have a history of psoriasis, or a family history of psoriasis, that would be one point for either of those. A negative rheumatoid factor would be a point, although some patients may have a positive rheumatoid factor, so thus they wouldn’t get a point. If they have a history of or current dactylitis, if they have nail changes, or if they have evidence on x-ray of their hands or feet of something called juxta-articular periostitis, then that’s a very specific feature that would get them a point. So, if you had three points from this list in a person with inflammatory arthritis, then that would give them the Caspar Criteria, which has a specificity of 99% and a sensitivity of 92%, which is very good for classification criteria.
The newest classification criteria for spondyloarthritis has been established by the ASAS 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 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.