Revised axial spondyloarthritis classification criteria remain elusive

DENVER – The revised axial spondyloarthritis classification criteria that U.S. rheumatologists say they desperately need remain elusive, with no firm path to creation.

The 2009 classification criteria for axial spondyloarthritis (SpA) developed by the Assessment of Spondyloarthritis international Society (ASAS) was a landmark in creating a definition for axial SpA to use when enrolling patients into clinical trials and to also potentially use for diagnosis.

But the 2009 classification criteria also have several shortcomings, especially from a U.S. perspective, that have limited the utility of the criteria in U.S. practice and studies.

^{Mitchel L. Zoler/Frontline Medical News}

Dr. Liron Caplan

Several years of discussions among North American rheumatologists about the classification criteria have produced consensus about what is wrong with them: The clinical elements of the criteria are not specific enough with sensitivity and specificity rates that are each about 80%-85%; the imaging component of the criteria is not totally up to date and as one example only considers osteitis and not other MRI abnormalities such as fatty metaplasia and T1 structural lesions; the criteria were entirely based on results from studies with Europeans, making their applicability to other patient types uncertain; and some terminology in the criteria are confusing, Liron Caplan, MD, said during a discussion of the criteria at the annual meeting of the of the Spondyloarthritis Research and Treatment Network.

But while the SpA experts who gathered at the meeting and who have also been discussing this issue since 2013 are of one mind on the problems, agreement on exactly how to solve them remains unresolved.

“Everything is still on the table,” said Dr. Caplan, a rheumatologist and director of the SpA program at the University of Colorado in Aurora.

A year ago, at SPARTAN’s prior annual meeting, circumstances looked on track for a quicker resolution. In a vote of the membership at the 2015 gathering, 64% backed creation of new classification criteria, and Dr. Caplan proposed quickly preparing a research proposal to present in early 2016 to the American College of Rheumatology and the European League Against Rheumatism for funding.

^{Mitchel L. Zoler/Frontline Medical News}

Dr. Atul A. Deodhar

But in the ensuing year, the effort got mired in discussions on how to perform the study needed to gather the evidence base for criteria revisions. Some progress occurred, most notably an agreement between SPARTAN officials and the ASAS leadership to work together on the revision, said Atul A. Deodhar, MD, professor of medicine and medical director of the rheumatology clinics at the Oregon Health & Science University in Portland.

The SPARTAN and ASAS representatives also agreed on several specifics of what’s needed, including a weighting formula for the 10 different clinical criteria of the SpA classification. Currently, in individuals with low back pain lasting 3 months or longer at an age of onset younger than 45 years, any one of these 10 clinical criteria can create a case of SpA either if combined with MRI or radiographic evidence of sacroiliitis, or without any imaging if the individual is HLA-B27 positive and fulfills two items from the 10-item list of clinical criteria.

It’s the lack of radiographic imaging confirmation, so-called “nonradiographic SpA,” that generates the greatest concern about below-par specificity and that may be helped by a weighting adjustment that varies the classification power of each of the 10 clinical items. A more ideal balance might be criteria with sensitivity reduced from the current level to about 70% and with specificity rising to about 90%, Dr. Caplan suggested.

The keystone of any revision will be a large, new study with SpA patients from various locations. Dr. Caplan emphasized that “no firm decisions have yet been made” regarding the study's name or research focus.

mzoler@frontlinemedcom.com

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This article was updated August 11, 2016.