Do the Provisional Paediatric Rheumatology International Trials Organisation Enthesitis/Spondylitis-Related Juvenile Idiopathic Arthritis Criteria Capture Youth With Axial Spondyloarthritis?

Objective: The Paediatric Rheumatology International Trials Organisation (PRINTO) recently undertook an effort to better harmonize the pediatric and adult arthritis criteria. These provisional criteria are being refined for optimal performance. We aimed to investigate differences between patients who did and did not fulfill these PRINTO criteria among youth diagnosed with juvenile spondyloarthritis (SpA) that met axial juvenile SpA (axJSpA) classification criteria. Methods: This was a retrospective cross-sectional sample of youth diagnosed with juvenile SpA who met the axJSpA classification criteria. Demographics, clinical manifestations, and physician and patient-reported outcomes were abstracted from medical records. Magnetic resonance imaging (MRI) scans underwent central imaging review by at least two central raters. Differences between groups were compared using Wilcoxon signed-rank test or chi-square test, as appropriate. Results: Of 158 patients who met axJSpA criteria, 107 patients (68%) met the PRINTO provisional criteria for enthesitis/spondylitis-related arthritis. A total of 41 patients (26%) did not fulfill any of the three major PRINTO criteria due to lack of peripheral disease manifestations. Demographics, prevalence of inflammatory or structural lesions on MRI, family history of SpA, and duration of pain were not statistically different between those who did and did not meet PRINTO criteria. Those who fulfilled the PRINTO criteria had significantly more peripheral arthritis, enthesitis, and HLA-B27 positivity but reported less sacral/buttock pain. Conclusion: Phenotypic differences of children with axJSpA between those who were and were not classified by the PRINTO criteria were primarily due to peripheral disease manifestations and HLA-B27 positivity. Modification of the PRINTO provisional criteria may facilitate capture of youth with primarily axial disease.