Background/Purpose: The distribution of Juvenile Idiopathic Arthritis (JIA) categories and disease severity at presentation vary across countries, however it is unclear how much of this variation is due to differences in healthcare systems. Canada’s universal healthcare system and multiculturalism offer a unique opportunity to assess the impact of ethnicity in a single setting where referral biases may be attenuated.

The objective of this study is to assess the association of self-reported ethnicity with the distribution of JIA categories and clinical Juvenile Arthritis Disease Activity Scores (cJADAS10) at initial presentation to pediatric rheumatology care in Canada.

Methods: Newly diagnosed JIA patients recruited into the Research in Arthritis in Canadian Children emphasizing Outcomes cohort (ReACCh-Out) from 2005 to 2010 reported their ethnicities. The cJADAS10 at enrolment was used as a proxy for disease severity at presentation to care. For each ethnicity, we compared the distribution of JIA categories and median cJADAS10 scores among three groups: children reporting only that ethnicity, children reporting that and other ethnicities, and children not reporting that ethnicity. We analyzed ethnicities reported by at least 10 participants. Chi-square tests assessed if any JIA category was under or overrepresented in a given ethnicity. We tested each JIA category with Fisher exact tests. P-values < 0.05 were considered significant and P-values below the threshold of the Bonferroni correction (p< 0.007) were considered a strong discovery signal. Kruskal-wallis tests compared median cJADAS10 scores and multivariable linear regression assessed the association of cJADAS10 scores with ethnicity, JIA categories and time from symptom onset to diagnosis.

Results: 1395 ReACCh-Out participants volunteered ethnicity data. Fifteen ethnic groups were reported by at least 10 ReACCh-Out participants each, four groups (Black, British, French, Indigenous) had statistically significant differences in distribution of JIA categories, and four (British, Eastern European, French, Indigenous) in cJADAS10 scores. British ethnicities had increased frequency of enthesitis related arthritis (ERA) and psoriatic arthritis with reduced frequency of oligoarthritis (Table 1). French ethnicities had increased frequency of oligoarthritis and decreased frequency of ERA. Indigenous and Black ethnicities had increased frequency of Rheumatoid Factor (RF)-positive polyarthritis. Median cJADAS10 scores were higher in children reporting British or Indigenous ethnicities, and lower in children reporting French or Eastern European ethnicities (Table 2). Associations of ethnicity with cJADAS10 scores were no longer significant in multivariable regression including JIA categories and time from symptom onset to diagnosis. There were no significant associations between these ethnicities and time from symptom onset to diagnosis.

Conclusion: Four of 15 ethnicities represented in this multiethnic cohort were associated with differences in JIA category distribution and severity at presentation. Differences in disease severity were largely explained by differences in JIA categories and time from symptom onset to diagnosis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/a-tale-of-many-canadas-associations-of-ethnicity-with-juvenile-idiopathic-arthritis-categories-and-disease-severity-at-presentation-in-a-multicultural-universal-healthcare-setting-results-from-reacc/