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Background: Recently, the updated version of the antiphospholipid syndrome (APS) 2023 ACR/EULAR criteria has been published 1. Objectives: To characterize the qualitative and quantitative variations in patient categorization and to examine the influence of the 2023 ACR/EULAR criteria in identifying patients included in a research cohort as having APS. Methods: The research cohorts included consecutive patients enrolled at SGB Hospital (Turin, Italy) and at the HCMNMRD (Córdoba, Argentina) over the last 3 years (Jan 2021-23). Patients had tested consistently positive for at least one antiphospholipid antibody (aPL) throughout the previous 3 years. To compare the Sydney and 2023 APS criteria, the first APS Sydney index event was considered and calculated. Results: 249 individuals made up the cohort (185 APS and 64 aPL carriers based on Sydney criteria). 146/185 subjects (78.9%) were classified as primary APS (PAPS), in 39 subjects (21.1%) APS was associated to another autoimmune disease (secondary APS, SAPS). The initial index event for the 185 patients was venous thrombosis (VT) in 55 cases (29.8%), arterial thrombosis (AT) in 63 cases (34%), and pregnancy morbidity (PM) in 67 cases (36.2%). 90 participants (48.7%) were unable to meet the new criteria's composite score once the modified criteria were applied. According to Sydney criteria, the percentage of thrombotic APS dropped from 47.3% to 34.9% in 23 cases due to high cardiovascular risk, 6 due to IgM aPL profile, and 2 patients due to both. The percentage of patients with PM dropped from 26.9 to 3.2% (20 occurrences of fetal losses and 39 cases of recurrent early pregnancy loss). The proportion of aPL carriers went from 26% to 61%. When looking at the disease evolution at follow-up, 32 additional patients out of 90 (35.6%) fulfilled the new criteria, after developing new clinical manifestation following index event. Additional clinical manifestations included: 4 venous events, 7 arterial events; 11 suspected livedo racemosa, 5 livedoid vasculopathy, 1 myocardial infarction; 3 foetal deaths, 13 severe preeclampsia and placental insufficiency, 5 early recurrent miscarriages; valvular thickening, 1 valvular vegetation; 6 thrombocytopenia. Considering both index event and subsequent event developed/identified during the follow-up, a total of 122 APS patients fulfilled both Sydney and 2023 classification criteria. It is noteworthy that new thrombotic events (N=11) happened while patients were receiving VKA medication, and further obstetric clinical symptoms (N=21) occurred despite standard of care treatment. Furthermore, independent of the concomitant presence of positivity for IgM isotypes, all participants who developed further clinical symptoms had an aPL profile that satisfied the new ACR/EULAR categorization criteria (i.e., single LA positivity, high titer of aCL IgG and/or aB2GPI IgG). Lastly, per the Sydney definition, none of the 64 aPL carriers met the requirements for APS in 2023. However, 8 aPL carriers presented thrombocytopenia (without other clinical manifestations). Conclusion: APS exerts unique challenges due to its low prevalence and the often-heterogeneous clinical manifestations. Healthcare providers, patients, and other stakeholders must carefully plan, communicate, and work together to manage the transition from the old categorization criteria to the new set of criteria for rare diseases. It will be necessary to use a multidisciplinary approach to evaluate how new criteria may affect research and, ultimately, patient care. Taking into consideration our cohort, quite few variations in the patients' classification when using the new APS 2023 criteria were detected. REFERENCES: 1 Barbhaiya M, Zuily S, Naden R, et al. 2023 ACR/EULAR Antiphospholipid Syndrome Classification Criteria. Arthritis Rheumatol (Hoboken, NJ) 2023. DOI:10.1002/ART.42624. Acknowledgements: NIL. Disclosure of Interests: None declared.
Foddai et al. (Sat,) studied this question.