Antiphospholipid Syndrome (APS) is a complex autoimmune disorder that presents significant diagnostic and management challenges, particularly in pregnancy. Recent work has provided new insights into diagnostics, classification, and prognosis of APS, which has led to a refined approach to patient care.

Refinements in APS Classification Criteria

A key advancement in APS diagnosis is the revision of classification criteria by the American College of Rheumatology (ACR) and the European League Against Rheumatism (EULAR), which introduced a weight-based model that prioritizes clinical and laboratory findings. The criteria emphasize the importance of differentiating obstetric APS from other manifestations, incorporating pregnancy-related complications such as fetal growth restriction and severe preeclampsia to better differentiate APS subtypes. Laboratory tests include lupus anticoagulant [LAC], IgG/IgM anticardiolipin antibodies [aCL], and IgG/IgM anti–glycoprotein I antibodies [anti-β2GPI], with at least one positive result required for classification. For a standardized approach, an enzyme-linked immunosorbent assay (ELISA) should be used for antiphospholipid antibody testing¹. Although the classification criteria are not equivalent to diagnostic criteria, their clinical relevance in guiding patient assessment and management is evident. To align these criteria with alternative commonly used platforms, a group of experts set its objective to improve harmonization between APS antibody ELISA and non-ELISA techniques².

APS Subgroups and Risk Stratification

As shown using machine learning-based clustering analysis, three distinct APS subgroups can be identified with a clear difference between obstetric and thrombotic APS, and for the latter, also a difference between men and women. Patients can be stratified based on clinical presentation and biomolecular markers, leading to more precise prognostic assessments. For example, some APS patients exhibit a predominant obstetric profile with high pregnancy morbidity but a lower risk of thrombosis, while others present with severe thrombotic complications, requiring more aggressive management strategies³.

Emerging Biomarkers for APS Diagnosis

New biomarkers for APS patients with vascular thrombosis and/or pregnancy complications are also improving risk assessment in diagnostics. LAC remains the most significant predictor of adverse pregnancy outcomes, including fetal growth restriction and recurrent miscarriage. In addition to the aCL, and anti-β2GPI, other specific antibodies, also known as non-criteria APS, are emerging as valuable tools for refining risk stratification⁴. Distinct antiphospholipid antibody profiles have been observed between patients with obstetric and those with thrombotic APS⁵. These biomarkers contribute to the growing emphasis on personalized treatment strategies, ensuring that high-risk patients receive tailored therapeutic interventions.

Conclusion

These advancements mark a significant step forward in APS diagnosis and management. The integration of refined classification systems, novel biomarkers, and machine learning-based patient stratification allows for more precise risk assessment and personalized treatment strategies. As research progresses, these findings will likely lead to improved clinical outcomes for APS patients, particularly in pregnancy.

1. Barbhaiya, et al. (2024). The 2023 ACR/EULAR Antiphospholipid Syndrome Classification Criteria ↩︎
2. Meroni, et al. (2025). American College of Rheumatology/European League Against Rheumatism antiphospholipid syndrome classification criteria solid phase-based antiphospholipid antibody domain-collaborative efforts of Antiphospholipid Syndrome Alliance for Clinical Trials and International Networking and ISTH SSC to harmonize enzyme-linked immunosorbent assay and non-enzyme-linked immunosorbent assay antiphospholipid antibody tests: communication from the ISTH SSC Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibodies ↩︎
3. Chen, et al. (2025). Identification of Three Distinct Subgroups in Antiphospholipid Syndrome: Implication for Sex Differences and Prognostic Outcomes from a Multicenter Study ↩︎
4. Murvai, et al. (2025). Antiphospholipid syndrome in pregnancy: a comprehensive literature review ↩︎
5. Anunciación-Llunell, et al. (2025). Differences in Antiphospholipid Antibody Profile between Patients with Obstetric and Thrombotic Antiphospholipid Syndrome ↩︎

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