0684: Single Antiphospholipid Antibody Positive Thrombotic APS Patients’ Clinical Characteristics: Retrospective Results from the APS ACTION Clinical Database and Repository (Registry)

Silvia Grazietta Foddai¹, Irene Cecchi², Massimo Radin¹, Danieli De Andrade³, Maria Tektonidou⁴, Vittorio Pengo⁵, Guillermo Ruiz-Irastorza⁶, H. Michael Belmont⁷, Maria Gerosa⁸, Paul Fortin⁹, Rosario Lopez-Pedrera¹⁰, Zhouli Zhang¹¹, Tatsuya Atsumi¹², Guilherme de Jesus¹³, Hannah Cohen¹⁴, Nina Kello¹⁵, Ware Branch¹⁶, Denis Wahl¹⁷, Laura Andreoli¹⁸, Esther Rodriguez¹⁹, Michelle Petri²⁰, Ann E. Clarke²¹, Ricard Cervera²², Jason Knight²³, Bahar Artim-Esen²⁴, Rohan Willis²⁵, Guillermo Pons-Estel²⁶, Doruk Erkan²⁷, Dario Roccatello¹ and Savino Sciascia², ¹University of Turin, Turin, Italy, ²University of Turin, Torino, Italy, ³University of São Paulo, São Paulo, Brazil, ⁴University of Athens, Athens, Greece, ⁵University of Padova, Padova, Italy, ⁶University of the Basque Country, Barakaldo, Spain, ⁷New York University School of Medicine, New York, NY, ⁸University of Milan, Milano, Italy, ⁹CHU de Québec Université Laval, Québec, QC, Canada, ¹⁰University of Cordoba, Cordoba, Spain, ¹¹Beijing Medical University, Beijing, China, ¹²Hokkaido University, Sapporo, Japan, ¹³Universidade do Estado do Rio de Janeiro, Rio De Janeiro, Brazil, ¹⁴University College London, London, United Kingdom, ¹⁵Northwell Health, New York, NY, ¹⁶University of Utah Health, Salt Lake City, ¹⁷Nancy University Hospital, Nancy, France, ¹⁸University of Brescia, Brescia, Italy, ¹⁹Hospital Universitario 12 de Octubre, Madrid, Spain, ²⁰Johns Hopkins University School of Medicine, Baltimore, MD, ²¹University of Calgary, Calgary, AB, Canada, ²²University of Barcelona, Barcelona, Spain, ²³University of Michigan, Ann Arbor, MI, ²⁴Istanbul University, Istanbul, Turkey, ²⁵University of Texas, Galveston, TX, ²⁶Centro Regional de Enfermedades Autoinmunes y Reumáticas, Rosario, Argentina, ²⁷Barbara Volcker Center for Women and Rheumatic Diseases, New York, NY

Background/Purpose: The APS ACTION is a network collecting and analyzing data ofaPL positive patients recruited by international centers. Based on the assumption that triple aPL-positive (LA, aCL IgG/M, and aβ2GPI IgG/M)patients are at higher risk for thrombosis, we investigated the clinical phenotypeof single aPL-positive(LA, aCL IgG/M, oraβ2GPI IgG/M) patients in a large cohort of primary thrombotic APS subjects.

Methods: APS ACTION Registry includes persistently aPL positive patients with or without other systemic autoimmune diseases. We screened the registry for primary thrombotic APS patientswith persistent single aPL positivity (defined as LA, aCL, and aβ2GPI results [from local laboratories] all available at registry entry with two consecutive resultsandonly one aPLtest being persistently positive in accordance to the revised Sapporo Criteria). For each patient, we assessed the site of the event, the type and isotype of aPL, and the number of retrospective documented recurrences. Single aPL-positive patients, with no history of thrombotic or obstetric APS, were used as a control group for comparing the prevalence of different isotypes.Basic statistical analysis was performed using SPSS 26.0.

Results: Of 427 primary APS patientscollected in the registry, 233 triple aPL-tested patients were included in the analysis and63/233(27%) had persistent single aPL positivity (66% women, 77% white): 45(71%) single LA positive, 9 (15%) single aCL(8 IgG,1 IgM), and 9 (15%) single aβ2GPI (7 IgG, 2 IgM). As a comparison, of 66 triple aPL-tested patients with no thrombotic or obstetric APS, 22 hadpersistent single aPL-positivity (68% women, 90% white): nine (41%) single LA positive, eight (36%) single aCL(3 IgG, 5 IgM), and five (23%) single aβ2GPI (2 IgG, 3 IgM). Single LA positivity was significantly more common in the thrombotic APS cohort compared toaPL carriers(71% Vs 41%, p:0.021).

Associations between different aPL tests and clinical manifestations are shown in Table 1. Among single aPL-positive patients with history of arterial or venous thrombosis, 68% and 75% had single LA-positivity, respectively. Based on small numbers, a trend for a higher frequency was observed: a) for arterial thrombosis in single aCL-positive patients(aCL+ 7/9 [78%] Vs. aCL- 2/9 [22%]);and b) for venous thrombosis insingle aB2GPI-positive patients (aβ2GPI+ 8/9 [89%] Vs aβ2GPI- [1/9] 11%).

A history of thrombosis recurrence was observed in 18(28%) patients. However, nosignificant difference was detected between aPL profile and recurrences (both for number and type of events).

Conclusion: Based on the analysis of an international persistently aPL-positive cohort with no other systemic autoimmune diseases: a) approximately 30% of patients have "single" aPL positivity) the majority of "single" aPL-positive patients have LA-positivity (64%), which is more frequent among those with thrombotic APS (71%), compared to those without APS classification (41%); and c) approximately one-third of "single" aPL-positive patients have history of recurrent thrombosis.
Table 1. Associations between different aPL tests and clinical manifestations.
Disclosures: S. Foddai, None; I. Cecchi, None; M. Radin, None; D. De Andrade, None; M. Tektonidou, None; V. Pengo, None; G. Ruiz-Irastorza, None; H. Belmont, None; M. Gerosa, None; P. Fortin, None; R. Lopez-Pedrera, None; Z. Zhang, None; T. Atsumi, None; G. de Jesus, None; H. Cohen, None; N. Kello, None; W. Branch, None; D. Wahl, None; L. Andreoli, None; E. Rodriguez, None; M. Petri, None; A. Clarke, None; R. Cervera, None; J. Knight, None; B. Artim-Esen, None; R. Willis, None; G. Pons-Estel, None; D. Erkan, None; D. Roccatello, None; S. Sciascia, None.