CO114 | ANTI-PS/PT IgM IDENTIFIES AN ANTIGEN-DEFINED SUBSET WITHIN LUPUS ANTICOAGULANT POSITIVITY ASSOCIATED WITH THROMBOTIC PHENOTYPE
Abstract
Background and Aims. Interpretation of isolated lupus anticoagulant (LAC) positivity remains challenging because LAC represents a functional coagulation abnormality rather than an antigen-defined immune response. Anti-phosphatidylserine/prothrombin (aPS/PT) antibodies have been proposed as non-criteria antiphospholipid antibodies that may refine serological characterization of LAC-positive patients. The study aims to determine whether aPS/PT antibodies identify antigen-defined subgroups associated with thrombotic phenotype among consecutive patients undergoing antiphospholipid antibody testing. Methods. We performed a retrospective two-center observational study including 131 consecutive adult patients referred for antiphospholipid antibody evaluation (Fig. 1). All underwent testing for LAC, anticardiolipin antibodies, anti-β2-glycoprotein I antibodies, and aPS/PT antibodies. Because antibody testing was performed after clinical events, thrombosis was analyzed as a historical clinical phenotype. Associations were assessed using stratified comparisons and logistic regression adjusted for age, sex, smoking status, and hypertension. Results. A history of objectively confirmed thrombosis was present in 72.1% of patients. aPS/PT IgM levels correlated with LAC activity measured by the dRVVT ratio. Patients positive for LAC and aPS/PT IgM but negative for anticardiolipin and anti-β2-glycoprotein I antibodies had significantly higher odds of prior thrombosis compared with the reference serological profile (adjusted OR 11.2; 95% CI 2.5–50.8; p = 0.002). Conclusions. In this selected tertiary referral cohort enriched for thrombotic disease, aPS/PT IgM identified a biologically and clinically distinct subset within LAC-positive patients associated with prior thrombosis. These findings support further prospective evaluation of aPS/PT testing for refinement of heterogeneous LAC positivity.
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BibTeX
@article{cristofaro2026co114,
title = {{CO114 | ANTI-PS/PT IgM IDENTIFIES AN ANTIGEN-DEFINED SUBSET WITHIN LUPUS ANTICOAGULANT POSITIVITY ASSOCIATED WITH THROMBOTIC PHENOTYPE}},
author = {Raimondo De Cristofaro},
journal = {Bleeding, Thrombosis and Vascular Biology},
year = {2026},
month = oct,
url = {https://www.btvb.org/btvb/article/view/816},
note = {CC BY-NC},
}
RIS
TY - JOUR
TI - CO114 | ANTI-PS/PT IgM IDENTIFIES AN ANTIGEN-DEFINED SUBSET WITHIN LUPUS ANTICOAGULANT POSITIVITY ASSOCIATED WITH THROMBOTIC PHENOTYPE
AU - Raimondo De Cristofaro
PY - 2026
DA - 2026/10/26
JO - Bleeding, Thrombosis and Vascular Biology
UR - https://www.btvb.org/btvb/article/view/816
AB - Background and Aims. Interpretation of isolated lupus anticoagulant (LAC) positivity remains challenging because LAC represents a functional coagulation abnormality rather than an antigen-defined immune response. Anti-phosphatidylserine/prothrombin (aPS/PT) antibodies have been proposed as non-criteria antiphospholipid antibodies that may refine serological characterization of LAC-positive patients. The study aims to determine whether aPS/PT antibodies identify antigen-defined subgroups associated with thrombotic phenotype among consecutive patients undergoing antiphospholipid antibody testing. Methods. We performed a retrospective two-center observational study including 131 consecutive adult patients referred for antiphospholipid antibody evaluation (Fig. 1). All underwent testing for LAC, anticardiolipin antibodies, anti-β2-glycoprotein I antibodies, and aPS/PT antibodies. Because antibody testing was performed after clinical events, thrombosis was analyzed as a historical clinical phenotype. Associations were assessed using stratified comparisons and logistic regression adjusted for age, sex, smoking status, and hypertension. Results. A history of objectively confirmed thrombosis was present in 72.1% of patients. aPS/PT IgM levels correlated with LAC activity measured by the dRVVT ratio. Patients positive for LAC and aPS/PT IgM but negative for anticardiolipin and anti-β2-glycoprotein I antibodies had significantly higher odds of prior thrombosis compared with the reference serological profile (adjusted OR 11.2; 95% CI 2.5–50.8; p = 0.002). Conclusions. In this selected tertiary referral cohort enriched for thrombotic disease, aPS/PT IgM identified a biologically and clinically distinct subset within LAC-positive patients associated with prior thrombosis. These findings support further prospective evaluation of aPS/PT testing for refinement of heterogeneous LAC positivity.
SN - 2785-5309
ER -