Antinuclear antibody-positive patients should be grouped as a separate category in the classification of juvenile idiopathic arthritis

Objective: We undertook this study to test the hypothesis that in the International League of Associations for Rheumatology (ILAR) classification of juvenile idiopathic arthritis (JIA), patients with similar characteristics can be classified into different categories. We sought to investigate whether antinuclear antibody (ANA)-positive patients having disease in the ILAR categories of oligoarthritis, rheumatoid factor-negative polyarthritis, psoriatic arthritis, and undifferentiated arthritis share homogeneous features and to compare these features with those of ANA-negative patients having the same categories of disease.

Methods: We identified JIA patients who had been followed up during a 22-year period. ANA positivity was defined as ≥2 positive results at a titer of ≥1:160. Demographic and clinical features were recorded retrospectively and compared between ANA-positive and ANA-negative patients.

Results: Of a total of 971 patients, 711 were ANA positive, 149 were ANA negative, and 111 had an indeterminate ANA status. Patients with indeterminate ANA status were excluded. ANA-positive patients in the different ILAR categories were similar in terms of age at disease presentation, female-to-male ratio, and frequency of asymmetric arthritis and iridocyclitis. Compared with ANA-positive patients, the ANA-negative group was older at disease presentation and had a lower prevalence of females, a lower frequency of iridocyclitis and asymmetric arthritis, a greater number of affected joints over time, and a different pattern of arthritis. The close relationship between the presence of ANAs and younger age at disease presentation, female predominance, asymmetric arthritis, development of iridocyclitis, lower number of affected joints over time, and lack of hip involvement was also confirmed by multivariate and multiple correspondence analysis.

Conclusion: Our findings substantiate the hypothesis that ANA-positive patients classified into different JIA categories by current ILAR criteria constitute a homogeneous patient population.