Application of the 2023 ACR/EULAR antiphospholipid syndrome classification criteria to patients fulfilling the 2006 revised Sapporo criteria.

Objectives: The American College of Rheumatology (ACR) and the European Alliance of Associations for Rheumatology (EULAR) developed new classification criteria for antiphospholipid syndrome (APS) in 2023. Although the new criteria yielded high specificity, further validation is needed in Asia, as the clinical characteristics of APS differ across ethnicities. We applied the 2023 ACR/EULAR criteria to Korean patients classified as having APS by the 2006 revised Sapporo criteria and assessed the concordance rate between the criteria.

Methods: For this study, 126 patients with APS were included. Clinical and laboratory data were reviewed, and the fulfilment of the 2023 ACR/EULAR criteria was assessed for each patient.

Results: Of the 126 patients classified by the 2006 revised Sapporo criteria, 107 had APS according to the 2023 ACR/EULAR criteria, accounting for a concordance rate of 84.9%. The concordance rate differed according to the index event. Patients with venous thromboembolism had the highest concordance rate (100%), followed by those with arterial thrombosis (76.4%). Patients with obstetric events had the lowest concordance rate (45.5%), attributable to the stricter obstetric criterion in the 2023 ACR/EULAR criteria than in the 2006 revised Sapporo criteria.

Conclusions: In Korean patients with APS, the concordance rate between the 2023 ACR/EULAR criteria and the 2006 revised Sapporo criteria was high. The concordance rate was considerably lower when confined to patients with obstetric APS. The 2023 ACR/EULAR criteria are stricter, particularly for obstetric events; its emphasis on specificity may result in the exclusion of patients with clinically significant obstetric APS.