Background/Purpose: The Paediatric Rheumatology International Trials Organisation (PRINTO) recently undertook an effort to better harmonize the pediatric and adult arthritis criteria. These provisional criteria are not validated and refinement may be necessary for optimal performance. We aimed to investigate differences amongst youth with clinically diagnosed juvenile SpA who met axJSpA classification criteria who did and did not fulfill the PRINTO provisional enthesitis/spondylitis-related criteria.

Methods: This was a retrospective cross-sectional sample of international youth who had juvenile SpA ascertained by the treating physician. All youth had onset of symptoms prior to age 18 and fulfilled the recently validated axJSpA classification criteria. The axJSpA classification criteria consist of 7 domains: imaging – active inflammation, imaging – structural lesions, pain chronicity, pain pattern, pain location, stiffness, and genetics/family history. A youth with juvenile SpA is classified as having axial disease with a cumulative score of ≥55 (out of 100). To meet the PRINTO criteria for enthesitis/spondylitis-related arthritis youth must fulfill one of 3 major criteria (Table 1). Data were abstracted from subjects’ medical records. All MRI scans underwent central imaging review by at least 2 central raters. Patient demographics, clinical manifestations, and physician and patient-reported outcomes were evaluated using standard descriptive statistics. Differences between groups were compared using Wilcoxon signed-rank test or chi-square as appropriate.

Results: Of 143 patients that met axJSpA criteria, 100 (69%) fulfilled the PRINTO provisional criteria for enthesitis/spondylitis-related arthritis. Thirty-four (23%) did not fulfill any of the 3 major PRINTO criteria due to lack of peripheral disease manifestations. The frequency with which each major and minor criteria were fulfilled is listed in Table 1. Demographics, family history of SpA, location of back pain, and duration of pain were not statistically different between those who did and did not meet PRINTO criteria (Table 2). Those who fulfilled the PRINTO criteria had significantly more morning stiffness lasting ≥15 minutes (p=0.02), peripheral arthritis (p< 0.01), enthesitis (p< 0.01), and HLA-B27 positivity (p=0.02). Patients who did not meet the PRINTO criteria had a significantly higher percentage of pain duration ≥12 weeks (p=0.01). There were no significant differences in the prevalence of inflammatory or structural lesions on MRI between the two groups (Table 3).

Conclusion: A third of children classified with axJSpA remain unclassifiable by the provisional PRINTO enthesitis/spondylitis-related criteria. The clinical and imaging manifestations of axial disease were not significantly different between those who did and did not fulfill the provisional PRINTO criteria. The phenotypic differences between those who were and were not classified by the provisional PRINTO criteria are confined to peripheral disease manifestations. Modification of the second major criterion of the PRINTO provisional criteria may facilitate capture of youth with primarily axial disease.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/printo-provisional-enthesitis-spondylitis-related-jia-criteria-performance-in-youth-classified-as-axial-disease-in-juvenile-spondyloarthritis/