A67: Factors That Contribute to Classification of Children as Having Undifferentiated Juvenile Idiopathic Arthritis

Abstract

Background/Purpose:According to the ILAR criteria, undifferentiated juvenile idiopathic arthritis (U‐JIA) includes children who fail to meet criteria for 1 of the other 6 categories or who meet criteria in more than 1 category. Classification requires category‐specific application of 5 exclusion criteria: 1. Psoriasis in the patient or a 1st degree relative; 2. Arthritis beginning after the 6th birthday in an HLA‐B27 + male; 3. HLAB27 associated disease in a 1st degree relative; 4. Rheumatoid factor positivity (RF+) on 2 occasions; and 5. The presence of systemic JIA (SoJIA).A pilot single‐centre study (n=21) revealed that psoriasis in a 1st degree relative was the most common reason for classifying patients as U‐JIA; disregarding this criterion would allow re‐classification of most U‐JIA patients and had no impact on the classification of JPsA patients (Chan et al., 2011). We aimed to determine the most frequent reasons for classifying children as U‐JIA from a large multicenter prospective cohort of children with JIA (n=1104).Methods:Two investigators reviewed data on patients diagnosed with UJIA extracted from the Research in Arthritis in Canadian Children emphasizing Outcomes (ReACCh‐Out) database. They identified by consensus the reasons for classifying patients as U‐JIA and the JIA category they would fall in if the following two changes were made: disregarding psoriasis in a 1st degree relative, considering patients as RF negative when only a single positive RF test was recorded.Results:84 patients (51 female), were classified as U‐JIA for the reasons shown in the . Exclusion criteria 1st degree relative with psoriasis (n=57) B27 male>6 years + arthritis (n=4) RF+ on 2 occasions (n=1) RF+ on 1 occasion only (n=17) 1st degree relative with B27 related disease (n=4) SoJIA (n=0) Fulfills criteria for 2 categories (n=2) Revised category if exclusion criteria disregarded Oligo 25 9 2 Poly RF− 13 2 Poly RF+ 5 (1 RF+x2, 4 RF+x1) ERA 12 5 Systemic 2 1 JPsA 4 1 U‐JIA 1 1 2 (JPsA + ERA)If the criterion of having a 1st degree relative with psoriasis was disregarded, 25 patients would be classified as oligo JIA, 13 poly RF−, 5 poly RF+, 12 ERA and 2 SoJIA. If a single positive RF test was considered to be insufficient to meet the ILAR criterion of RF positivity, 9 patients would be re‐classified as oligo JIA, 5 ERA, 1 SoJIA, 1 JPsA and 1 would remain U‐JIA.Conclusion:Psoriasis in a 1st degree relative is the most common factor contributing to the classification of a child as having U‐JIA and removing it from the existing criteria should be considered. The presence of a single positive test for RF was the second most common reason resulting in a classification of U‐JIA. Definitive RF testing (two tests) should be maintained to satisfy the criterion of “RF positivity”.