Background/Purpose:   Disease flares are a concern to patients with JIA, their parents, and caregivers alike; but little is known of disease manifestations during a flare in children who have achieved inactive disease (ID) or whether flares differ among subtypes.  The aim of this study is to describe flares in children with JIA and determine differences in flare characteristics among JIA subtypes. 

Methods:    We studied children diagnosed with JIA between 2005 and 2010 who had at least one visit with ID (no active joints, no extra-articular manifestation, and a physician global assessment < 10mm) while being prospectively followed in the Research in Arthritis in Canadian Children emphasizing Outcomes (ReACCh-Out) cohort. They received usual pediatric rheumatology care at 16 Canadian centres.  Flare was defined as loss of any criteria for ID. In addition a flare was imputed on the basis of an intra-articular injection alone in absence of other documentation of disease activity.  Treatment of flares were recorded if there was a change, addition, or restart of anti-rheumatic or anti-uveitis treatment.

Results: Of 1492 children recruited in ReACCh-Out, 1146 had at least one visit with ID, with median follow-up of 24 mo (IQR 12,39) following first record of ID.   A total of 1,191 flares were observed in 531 children (46.3%) after their first ID episode: 31% with systemic  JIA and 44-50% with other subtypes.   Arthritis was a feature of the majority of flares but there were significant differences in frequencies across subtypes (p=0.001).  Frequencies of nonarticular flares also differed among subtypes (p<0.001) and were most common in children with systemic, enthesitis related arthritis and undifferentiated subtypes.  Flares due to uveitis were seen in patients with oligoarticular, rheumatoid factor negative, and undifferentiated subtype most commonly.  The majority of flares occurred while patients were still on treatment for their JIA and overall 45% were not associated with treatment changes (Table).

Table:  Characteristics of disease flare across JIA subtypes

Feature	All	Systemic	Oligo	RF neg	RF pos	Psoriatic	ERA	Undiff
# subjects	1146	68	488	212	35	75	155	113
# subjects with flare	531	21	232	106	17	36	69	50
# flares	1191	82	483	233	56	70	133	134
Flare signs (% of flares):
Arthritis flares	79	58.5	83	85	93	86	63	72
Non-articular   flares	18	41.5	13	12	7	14	35	22
PGA ≥ 1 without   other signs	10	29	8	7	7	9	13.5	7.5
Treatment at time of flare (% of flares):
Flare on treatment	70	91.5	56.5	83	86	60	78	71
Flare off  treatment	27	7	39	15.5	14	40	19.5	25
No change in   treatment   following flare	45	66	40	48	50	46	48	37

Conclusion:  Flare characteristics in JIA differ among disease subtypes.  An increase in PGA alone accounts for flare some patients, suggesting that PGA includes consideration of disease manifestations not included in our flare definition.  Our results suggest that while disease flares occur in approximately half of children with JIA managed with usual care, many are mild and require no treatment change.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/flares-in-children-with-jia-results-from-the-reacch-out-cohort/