CO100 | ANTIPHOSPHATIDYLSERINE–PROTHROMBIN ANTIBODIES IN ANTIPHOSPHOLIPID SYNDROME: CLINICAL ASSOCIATIONS AND DIAGNOSTIC GAPS MAPPED BY A SCOPING REVIEW

H. Parikh¹, G. Gobbo^2|3, F. Albiero^2|3, J. Dass⁴, E. Esteve-Valverde^5|6, J. Alijotas-Reig^5|7, P. Simioni^2|3, A. Hoxha^2|3 | ¹Hemato-Oncology Clinic Vedanta, Ahmedabad, India; ²Department of Medicine (DIMED), University of Padua, Italy; ³Internal Medicine Unit and Thrombotic and Bleeding Disorder Centre, University Hospital of Padua, Padova, Italy; ⁴Department of Hematology, All India Institute of Medical Sciences, New Delhi, India; ⁵Vall d'Hebron Research Institute, Vall d'Hebron Hospital Campus, Barcelona, Spain; ⁶Systemic Autoimmune Diseases Unit, Department of Medicine, Hospital Sant Camil, Consorci Sanitari Alt-Penedes-Garraf, Sant Pere de Ribas, Barcelona, Spain; ⁷Department of Medicine, Universitat Autonoma, Barcelona, Spain

Background and Aims. Antiphospholipid syndrome (APS) is a systemic autoimmune thromboinflammatory disorder characterized by thrombosis and/or pregnancy morbidity in association with antiphospholipid antibodies (aPL). As no single laboratory test serves as a diagnostic gold standard, non-criteria antibodies such as antiphosphatidylserine–prothrombin (aPS/PT) have been proposed to complement conventional testing, though their clinical utility remains inconsistently reported. This scoping review mapped the clinical and laboratory relevance of aPS/PT in APS, including seronegative APS, while identifying diagnostic gaps, methodological heterogeneity, and key uncertainties.
Methods. A scoping review was conducted in accordance with PRISMA-ScR guidance and prospectively registered on the Open Science Framework (OSF; doi:10.17605/OSF.IO/FSJ8Z). A systematic search of PubMed, Scopus, Embase, and Web of Science identified 1,540 records using predefined strategies. After removal of 1,080 duplicates, title/abstract screening, and full-text review, 58 studies were selected for data extraction. Screening was performed using the Rayyan software. Data were extracted using a structured electronic form and synthesized descriptively.
Results. A total of fifty-eight studies were incorporated, predominantly single-center (53 out of 58) and retrospective (34/58), spanning 1988–2023. The majority examined IgG and IgM aPS/PT (52/58), exhibiting considerable geographic and methodological heterogeneity. Only fourteen studies distinctly distinguished primary antiphospholipid syndrome (APS), secondary APS, non-APS, and disease controls, whereas most investigations depended on mixed or outcome-driven cohorts. Commercial assays were predominant (42 out of 58), primarily from Werfen; however, cut-off definitions varied considerably, even within identical kit types. Persistence and titers of aPS/PT were infrequently evaluated. Lupus anticoagulant was assessed in fifty-five studies employing diverse methodologies. Among thirty-five studies assessing concordance, aPS/PT demonstrated a positive correlation with lupus anticoagulant in thirty-one, although multivariable adjustment was uncommon. Associations with thrombosis and pregnancy morbidity were frequently reported but lacked consistent definitions and analytical approaches.
Conclusions. aPS/PT demonstrates a reproducible trend toward association with APS-related laboratory and clinical outcomes; however, marked heterogeneity in cohort definitions, patient selection, assay platforms, cut-off determination, and limited multivariable analyses underscores substantial scope for methodological harmonization and standardized statistical approaches to improve confidence in interpreting this widely discussed non-criteria antibody.