Evaluation of ILAR and PRINTO classifications for juvenile idiopathic arthritis: oligoarticular JIA vs early-onset ANA-positive JIA.

Objectives: The International League of Associations for Rheumatology (ILAR) juvenile idiopathic arthritis (JIA) classification was revisited by the Pediatric Rheumatology International Trials Organization (PRINTO) in 2018. Classifications should establish uniform groups to assist physicians in providing optimal care. Therefore, we evaluated changes proposed by PRINTO to highlight their impact on forming consistent groups regarding uveitis and treatment responses, particularly focusing on early-onset anti-nuclear antibody (ANA)-positive JIA.

Methods: Pediatric patients diagnosed with JIA according to ILAR and PRINTO classification, with a minimum of 1-year of follow-up, were enrolled, excluding those meeting the exclusion criteria for both the oligoarticular JIA and the early-onset ANA-positive JIA groups.

Results: Among the 139 enrolled patients, 110 (79.1%) had oligoarticular JIA, while 15 (10.8%) had early-onset ANA-positive JIA. The below-age-5 criterion demonstrated the strongest association with uveitis, while the below-age-7 provided similar associations without substantial exclusions (odds ratio (OR) 8.62 [2.50-29.81] vs 7.45 [2.37-26.66]). Patients with a single ANA positivity at a titer ≥ 1/160 and age of onset below 7 had a notably higher risk of new-onset uveitis and biologic DMARD requirement (OR 7.95 [2.37-26.66] and 3.6 [1.42-9.09], respectively).

Conclusion: The inclusion of age of disease onset and ANA positivity with a titer ≥ 1/160 has enhanced uniformity in uveitis risk and treatment response, including failure of conventional synthetic DMARDs. Additionally, a single ANA positivity at a ≥ 1/160 titer rather than requiring two instances yields similar consistency. However, the joint count criteria failed to form consistent groups. PRINTO's classification places a significant proportion of patients into the "other JIA" group, necessitating further classification for improved clinical utility. Key Points •Inclusion of age and ANA positivity criteria increased uniformity among the subgroups. •Single ANA positivity at a ≥ 1/160 titer can be sufficient instead of twice. •Early utilization of bDMARDs may be beneficial for early-onset ANA-positive JIA group. •PRINTO classification must further classify the "other JIA" before being implemented in clinical practice.