COMPARATIVE EVALUATION OF THE PERFORMANCE OF REVISED SAPPORO AND 2023 ACR/EULAR CLASSIFICATION CRITERIA IN CHILDHOOD-ONSET ANTIPHOSPHOLIPID SYNDROME

PV019 / #134 Poster Topic: AS03 - Antiphospholipid Syndrome Background/Purpose Antiphospholipid syndrome (APS) is a systemic autoimmune disease characterized by increased risk of thrombosis and pregnancy morbidity with persistently elevated antiphospholipid antibodies (aPL). Childhood APS is usually diagnosed before age 18. Historically, APS has been classified using the Sapporo criteria, revised in 2006. The American College of Rheumatology (ACR) and European Alliance of Rheumatology Associations (EULAR) developed new classification criteria for APS in 2023 for research. Here we characterized a single-center cohort of adolescents and young adults (AYA) with childhood-onset APS, diagnosed by expert opinion. We compared the performance of the new 2023 ACR/EULAR criteria, which have not yet been tested in childhood APS vs. the revised Sapporo criteria. Methods We screened our childhood-onset connective tissue disease clinical service database comprising 215 cases to identify AYA diagnosed with childhood-onset APS based on expert opinion. We collected retrospective data to assess their demographics, disease duration, clinical manifestations, serological markers, treatment, and compared the 2 classification criteria. Results We identified 12 AYA diagnosed with childhood-onset APS (see Table 1 below), 91% of which had another associated autoimmune disease, including childhood-onset systemic lupus erythematosus (cSLE)/Sjögren and juvenile dermatomyositis (JDM). For APS manifestations, 8/12 cases were treated with aspirin and warfarin and 2/12 with direct oral anticoagulants (DOACs). One young person had previously received plasma exchange for catastrophic APS. 5/215 cases of AYA had persistently elevated aPL (4 with cSLE and 1 with JDM) without clinical APS manifestations (fulfilling neither the Sapporo nor the 2023 ACR/EULAR criteria for APS). Table 1: Summary of persistent aPL positive cases with childhood APS Conclusions The 2023 ACR/EULAR classified 75%, while the revised Sapporo criteria classified 66% of AYA with APS diagnosed by expert opinion, suggesting that childhood-specific criteria may be warranted. In this small cohort, macrovascular thrombosis affected 66% of AYA diagnosed with APS, and 33% had more than 1 major thrombotic event. Overall, 47% (8/17) of AYA with persistently elevated aPL had thrombosis, despite previous publications suggesting low risk of thrombosis in childhood APS. This cohort was followed up for 3-20 years, allowing us to assess the clinical course of this rare disease phenotype in children. Our findings challenged some of the previous assumptions about the lack of severity of this condition in people of younger age. Future large cohort studies are required to define the natural course and outcomes of childhood APS, as well as optimal long-term management strategies.