Performance Validation of the 2023 American College of Rheumatology/European League Against Rheumatism Antiphospholipid Syndrome Classification Criteria in an Antiphospholipid Syndrome Cohort

Background: The 2023 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) antiphospholipid syndrome (APS) classi fication criteria were developed with higher speci ficity but lower sensitivity compared with the 2006 Sydney revised classi fication criteria. Objectives: To validate the performance of the 2023 ACR/EULAR APS classi fication criteria in a large Chinese APS cohort. Methods: This was a single -center cohort study. Inclusion criteria aligned with the entry criteria of 2023 criteria. APS classi fication by "expert consensus panel " served as the gold standard. Sensitivity and speci ficity 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 whom 366 (69.58%) were female and 182 (34.60%) had systemic lupus erythematosus (SLE). Among them, 407 (77.38%) patients were classi fied as APS by experts. The 2023 criteria demonstrated higher overall speci ficity 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). Reduced sensitivity of the 2023 criteria was linked to the omission of certain microvascular manifestations, a stricter de finition of pregnancy morbidity, and the exclusion of isolated thrombocytopenia and isolated IgM isotype antiphospholipid antibodies from meeting clinical and laboratory criteria, respectively. Conclusion: The 2023 criteria offer higher overall speci ficity and improved sensitivity in speci fic patient subsets, such as those with SLE, microvascular manifestations, cardiac valve disease, and thrombocytopenia when compared with the 2006 criteria.