Classification of Nonsystemic Juvenile Idiopathic Arthritis Using the Provisional Paediatric Rheumatology International Trials Organisation Criteria

OBJECTIVE: This study aimed to retrospectively evaluate the provisional Paediatric Rheumatology International Trials Organisation (PRINTO) criteria in patients with juvenile idiopathic arthritis (JIA) classified according to the International League of Associations for Rheumatology (ILAR) criteria. METHODS: This retrospective cohort study was conducted at a single tertiary pediatric rheumatology center. In total, 310 patients with nonsystemic JIA were classified according to both ILAR and provisional PRINTO criteria. Demographic, clinical, and laboratory features were recorded, and the distribution of JIA categories under both classification systems was analyzed. RESULTS: The mean age at study enrollment was 169.8 (SD 59.2) months. Using ILAR criteria, 136 patients (43.9%) were categorized as having oligoarticular JIA, 73 (23.5%) enthesitis-related arthritis, 34 (11%) rheumatoid factor (RF)-negative polyarticular JIA, 12 (3.9%) psoriatic arthritis (PsA), 7 (2.3%) RF-positive polyarticular JIA, and 48 (15.5%) undifferentiated JIA. The provisional PRINTO criteria classified 107 (34.5%) patients with early-onset antinuclear antibody-positive JIA, 93 (30%) other JIA, 88 (28.4%) enthesitis/spondylitis-related JIA, 17 (5.5%) RF-positive JIA, and 5 (1.6%) unclassified JIA. The other JIA category included 93 patients, consisting of those with oligoarticular JIA (54.8%), RF-negative polyarticular JIA (21.5%), undifferentiated JIA (11.8%), enthesitis-related arthritis (6.5%), and PsA (5.4%) under the ILAR classification system. CONCLUSION: The provisional PRINTO criteria successfully reclassified a substantial proportion of previously undifferentiated JIA cases, improving diagnostic categorization by addressing some ILAR classification limitations. However, the high number of patients in the other JIA group highlights a potential limitation of the new system, warranting further investigation.