MADRID — Despite differences in required criteria, both the modified New York (mNY) and the Assessment of Spondyloarthritis International Society (ASAS) criteria are interchangeable for patients with axial spondyloarthritis (axSpA) with radiographic sacroiliitis, according to research presented at the 2019 European League Against Rheumatism (EULAR) Congress, held June 12-15, in Madrid, Spain.  

Patients classified with the mNY criteria are referred to as having ankylosing spondylitis and those classified with the ASAS criteria are referred to as having radiographic axSpA. Researchers sought to investigate the proportion of patients with axSpA and radiographic sacroiliitis who fulfilled both the mNY and the ASAS radiographic axSpA criteria to determine if the criteria are interchangeable.

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Data from patients with an axSpA diagnosis and definite radiographic sacroiliitis were pulled from 8 cohorts; however, data analysis was restricted for the Esperanza and OASIS cohorts due to unavailable information relating to individual items of the mNY criteria. Researchers then calculated how many patients from these cohorts fulfilled the mNY and/or the ASAS radiographic axSpA criteria.

Overall, 3882 patients fulfilled the mNY criteria, and 3434 patients fulfilled the ASAS radiographic axSpA criteria. Of the patients who met mNY criteria, 93% also met ASAS radiographic axSpA criteria; similarly, 96% of patients who met the ASAS radiographic axSpA criteria also fulfilled the mNY criteria.

A total of 89% of patients with both axSpA and radiographic sacroiliitis met both sets of criteria, while 7% met only mNY, 3% met only ASAS radiographic axSpA, and 1% met neither set of criteria.

The primary difference between the 2 sets of criteria was the reported age at onset of back pain. Patients older than 45 years at onset of back pain cannot fulfill ASAS criteria. Of the mNY patients who did not fulfill the ASAS radiographic axSpA criteria, 96% of cases were due to the age requirement, and 4% of cases were due to the lack of spondyloarthritis features.

Ninety percent of patients who met the ASAS radiographic axSpA criteria also met the mNY criteria due to the presence of inflammatory back pain. An additional 6% met the criteria due to a mobility restriction, despite not having inflammatory back pain. The remaining 4% of patients had neither inflammatory back pain nor mobility restriction but had other features of spondyloarthritis.

“These findings support the interchangeable use of the terms [radiographic] axSpA and [ankylosing spondylitis], which was also approved by a vote of ASAS members at the 2019 annual workshop in Amsterdam,” the researchers of the study concluded.

Disclosure: Drs van der Heijde, Ciurea, Dougados, Gensler, Poddubnyy, Rudwaleit, and Ramiro disclosed affiliations with pharmaceutical companies. For a complete list of disclosures, please see the full abstract online.

Reference

Boel A, Moltó A, van der Heijde D, et al. Are the modified New York and ASAS axial spondyloarthritis criteria interchangeable in the classification of spondyloarthritis paients with radiographic sacroiliitis: comparison in 8 cohorts? Presented at: European League Against Rheumatism (EULAR) Congress 2019; June 12-15, 2019; Madrid, Spain. Abstract OP0031.