Pos1167 Associations Between Criteria Items in Sle Patients in the Eular/Acr Classification Criteria Cohort

Background: During the development of the EULAR/ACR classification criteria for systemic lupus erythematosus (SLE), associations between items were analyzed in the early SLE cohort and the Eurolupus cohort [1]. Meaningful associations were found between items within organ systems, but not between organ systems, leading to the domains of the criteria. Objectives: To revisit the question of associations within the EULAR/ACR classification criteria cohort. Methods: Complete data on the presence or absence of every one of the 23 single EULAR/ACR classification criteria items were analyzed for all of the 1,197 SLE patients of the EULAR/ACR cohort [2], independent of their reaching or not reaching classification. Associations between individual items were analyzed in an unbiased approach. In this 23x23 table, associations were accordingly tested for 529 pairs, and, by Bonferroni's correction, significance was defined as a p-value <9.45e⁻⁵. Results: After correcting for the 529 comparisons, 29 correlations remained significant (Table 1). With the exception of C3 AND C4 low and C3 OR C4 low, which are, by definition, mutually exclusive, correlations within the domains were always stronger. Associations between items of different domains were weak, with correlation coefficients of 0.12 to 0.25. We found correlations between proteinuria and both antibodies to double-stranded DNA (dsDNA) and low complements, apparently driven by proliferative lupus nephritis (Table 1). Proteinuria was associated with hemolytic anemia. Low complements were associated with antibodies to dsDNA and Sm and with autoimmune cytopenias. Pleural or pericardial effusion was associated with fever (r= 0.12) and non-scarring alopecia with anti-Sm antibodies (r=0.13). Joint involvement was negatively correlated with lupus nephritis (r=-0.13 to -0.16) and thrombocytopenia (r=-0.14). Conclusion: These results underline the relevance of the EULAR/ACR SLE criteria domain structure. The association between anti-Sm and non-scarring alopecia, the association of serositis and fever, and the negative association between joint involvement and both nephritis and thrombocytopenia are of interest and warrant further investigation. REFERENCES: [1] Touma et al, Arthritis Care Res (Hoboken) 2020; 72: 1820-1826. [2] Aringer et al, Ann Rheum Dis 2019; 78: 1151-1159. Acknowledgements: The SLE classification criteria project was jointly supported by EULAR and the ACR. Disclosure of Interests: None declared.