Skip to main content
ACR Convergence 2025 Main banner
Final Program


Schedule at a Glance
Legend
Presentation Icons
CME
CME
Non-CME
Non-CME
In Person
In Person
On Demand
On Demand
Live Stream
Live Stream
Active Learning
Active Learning
Choose Rheum
Choose Rheum
Emerging Investigator Awardee
Emerging Investigator Awardee

Poster Session

Antiphospholipid Syndrome

Poster Session A

Session: (0115–0144) Antiphospholipid Syndrome Poster

0121: The Prevalence and Clinical Significance of IgA Anticardiolipin and Anti-β2-Glycoprotein-I Antibody Isotypes in Antiphospholipid Antibody Positive Patients: Descriptive Results from the Antiphospholipid Syndrome Alliance for Clinical Trials and International Networking Registry

Sunday, October 26, 2025
10:30 AM - 12:30 PM Central Time
Location: Hall F1

    Abstract Poster Presenter(s)

  • ES

    Emre Sahin, MD

    Hospital for Special Surgery
    New York, New York, United States

    Disclosure(s): No financial relationships with ineligible companies to disclose


Background/Purpose: The 2023 ACR/EULAR Antiphospholipid Syndrome (APS) Classification Criteria (CC) focus on IgG and IgM anticardiolipin (aCL) and anti-β2-glycoprotein-I antibodies (aβ2GPI). IgA isotypes were excluded due to limited evidence linking isolated IgA positivity to thrombosis, uncertain incremental value beyond established criteria, and a lack of assay standardization. However, emerging data from the general population suggest that individuals with IgA aβ2GPI may face an elevated risk of atherosclerotic cardiovascular disease, potentially due to impaired cholesterol efflux capacity and endothelial injury. Our primary objective was to compare the demographic, clinical, and laboratory characteristics of aCL and/or aβ2GPI IgA-positive versus IgA-negative patients. A secondary objective was to identify clinical and serological factors independently associated with IgA positivity.









Methods: The APS ACTION registry uses a web-based system to capture patient demographics, APS-related history, and medications. Inclusion requires aPL positivity per Revised Sapporo APS CC, confirmed within one year prior to enrollment. Patients are followed every 12±3 months with clinical assessments and blood collection. For this cross-sectional analysis of baseline data, we first compared demographic, clinical, and laboratory features between IgA-positive (aCL and/or aβ2GPI IgA >20 U; analysis repeated with >40 U cutoff) and IgA-negative (< 20 U) patients using chi-square or Fisher’s exact tests, based on APS ACTION Core Lab results (BioFlash, Werfen). We then conducted multivariate logistic regression to identify factors independently associated with IgA positivity.



Results: Of 1,252 patients recruited as of January 2025, 706 (56%) had baseline aCL/aβ2GPI IgA results. Using the >20U threshold recommended by the manufacturer, the IgA-positive group (n: 238 [34%]) had significantly higher rates of venous events, thrombocytopenia, heart valve disease, and triple/double aPL-positivity. Diabetes, hyperlipidemia, and single aPL-positivity were significantly higher in IgA-negative group (Table 1). In the multivariate analysis, after adjusting for the aPL profile, history of venous events, heart valve disease, thrombocytopenia, systemic lupus erythematosus (SLE), and any traditional cardiovascular disease risk factor, IgA-positivity was significantly associated with triple/double aPL-positivity, SLE, and thrombocytopenia (Table 2). When the IgA positivity cut-off of > 40U used: a) there was no change in the univariate results, except that diabetes, and hyperlipidemia no longer differed between the groups; and b) in multivariate analysis, IgA-positivity was significantly associated with triple/double aPL-positivity and history of venous events (data not shown).



Conclusion: In our well-established international cohort of persistently aPL-positive (lupus anticoagulant, aCL IgG/M, and/or aβ2GPI IgG/M) patients, concomitant aCL/aβ2GPI IgA-positivity correlates with a more severe clinical and, especially, serological phenotype. Future prospective analysis of the registry will help us further clarify the clinical significance of aCL/aβ2GPI IgA antibodies in aPL-positive patients.