Op0258 Performance Validation of the 2023 Acr/Eular Antiphospholipid Syndrome Classification Criteria in an Antiphospholipid Syndrome Cohort

Background: The 2023 ACR/EULAR Antiphospholipid Syndrome (APS) classification criteria were developed with higher specificity but lower sensitivity compared to the 2006 Sydney revised classification criteria. The validation in a larger cohort, particularly in specific ethnic groups (e.g., Asian populations) and among those with comorbid conditions (e.g., systemic lupus erythematosus) is vital to clarify both specificity and sensitivity and to address potential limitations. Objectives: This study was conducted to validate the performance of the 2023 ACR/EULAR APS classification criteria in a large Chinese APS cohort and in various subgroups. Methods: This was a single-center cohort study, conducted at the Department of Rheumatology and Clinical Immunology, Peking Union Medical College Hospital, from June 2012 to August 2023. Patients referred with suspected APS were prospectively enrolled and underwent regular follow-ups at 3- and 6-month intervals. Inclusion criteria aligned with the entry criteria of 2023 criteria. APS classification by multidisciplinary experts served as the gold standard. Sensitivity and specificity were compared between the 2023 and 2006 criteria. Results: A total of 526 patients with a mean age of 38.55±12.67 years were enrolled, of which 366 (69.58%) were female and 182 (34.6%) had systemic lupus erythematosus (SLE). Among them, 407 (77.4%) patients were classified as APS by experts, 335 (63.7%) patients met the 2023 criteria, while 353 (67.1%) met the 2006 criteria. The distributions of clinical domains in 2023 criteria exhibited variations across subgroups, including sex, age, disease duration, and underlying disease, as shown in Figure 1. Female patients displayed a higher prevalence of Domains 4, 5, and 6. Patients over 50 years old were more likely to have Domain 2. A shorter disease duration was associated with a higher prevalence of Domain 2, and longer durations were linked to increased prevalence of Domains 4 and 5. In patients with SLE, Domains 3, 4, 5, and 6 were more commonly observed. The 2023 criteria demonstrated higher overall specificity than the 2006 criteria (0.983 vs. 0.950), while sensitivity was relatively lower (0.818 vs. 0.853). The sensitivity of the 2023 criteria improved for patients with SLE (0.860 vs. 0.825), microvascular manifestations (0.867 vs. 0.786), cardiac valve disease (0.903 vs. 0.774), and thrombocytopenia (0.811 vs. 0.790). Among the 74 patients who met the gold standard but did not meet the 2023 criteria, 27 (36.5%) failed to meet the laboratory criteria, while 54 (73.0%) did not fulfill the clinical criteria. In the subset of 27 patients who did not meet the 2023 laboratory criteria, 16 (59.3%) exhibited moderate or high positive IgM. The 54 patients who did not meet the 2023 clinical criteria had a high prevalence of microvascular manifestations (11, 20.4%), pregnancy morbidity (23, 42.6%), and thrombocytopenia (36, 66.7%). Conclusion: The 2023 criteria offer higher overall specificity and improved sensitivity in specific patient subsets, such as those with SLE, microvascular manifestations, cardiac valve disease, and thrombocytopenia when compared to the 2006 criteria. Further studies are needed to determine the specificity of other microvascular manifestations, pregnancy morbidity, thrombocytopenia and IgM isotype aPLs as well as their potential inclusion in future classification criteria. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: None declared.