Antiphospholipid Syndrome Classification Research Articles

THE PERFORMANCE OF 2023 AMERICAN COLLEGE OF RHEUMATOLOGY (ACR) / EUROPEAN ALLIANCE OF ASSOCIATIONS FOR RHEUMATOLOGY (EULAR) ANTIPHOSPHOLIPID SYNDROME CLASSIFICATION CRITERIA IN A REAL-WORLD RHEUMATOLOGY DEPARTMENT

Background: Antiphospholipid Syndrome (APS) is one of the most common acquired causes of hypercoagulability. The 2023 American College of Rheumatology (ACR) / European Alliance of Associations for Rheumatology (EULAR) APS Classification Criteria were specified as new APS classification criteria with high specificity for use in observational studies and research. The primary objective of this study was to evaluate the performance of the 2023 ACR/EULAR APS classification criteria in a real-world rheumatology department. Methods: This is a retrospective, single-center study evaluating the sensitivity and specificity of the 2006 revised Sapporo and 2023 ACR/EULAR APS classification criteria in patients diagnosed with APS by clinical evaluation. A total of 184 patients, 103 of whom were diagnosed with APS, were included in the study. Results: The 2023 ACR/EULAR APS classification criteria demonstrate higher specificity 98.8% (95% CI 93.3-99.8) and positive predictive value (PPV) 98.7% (95% CI 93.2-99.8), whereas the revised Sapporo criteria exhibit higher sensitivity 90.3% (95% CI 83-96.6), negative predictive value (NPV) 88.1% (95% CI 79.4-93.4), and accuracy 90.8% (95% CI 85.7-94.1). When the diagnosis of APS was accepted according to the revised Sapporo criteria, the sensitivity of the 2023 ACR/EULAR APS classification criteria was 77% (95% CI 67.8-84.2), specificity 97.6% (95% CI 91.7-99.3), PPV 97.5% (95% CI 69.3-84.9) and NPV 78.1% (95% CI 69.3-84.9). Conclusion: The 2023 ACR/EULAR APS classification criteria have low sensitivity and high specificity compared to the revised Sapporo APS classification criteria. The increase in specificity is due to risk assessment in thromboses and strict obstetric and laboratory criteria.

Thrombosis in Antiphospholipid Syndrome: Current Perspectives and Challenges in Laboratory Testing for Antiphospholipid Antibodies.

Antiphospholipid syndrome (APS) diagnosis hinges on identifying antiphospholipid antibodies (aPL). Currently, laboratory testing encompasses lupus anticoagulant (LA), anticardiolipin (aCL), and anti-β2-glycoprotein I antibodies (aβ2GPI) IgG or IgM, which are included in the APS classification criteria. All the assays needed to detect aPL antibodies have methodological concerns. LA testing remains challenging due to its complexity and susceptibility to interference from anticoagulant therapy. Solid phase assays for aCL and aβ2GPI exhibit discrepancies between different assays. Antibody profiles aid in identifying the patients at risk for thrombosis through integrated interpretation of all positive aPL tests. Antibodies targeting domain I of β2-glycoprotein and antiphosphatidylserine-prothrombin antibodies have been evaluated for their role in thrombotic APS but are not yet included in the APS criteria. Detecting these antibodies may help patients with incomplete antibody profiles and stratify the risk of APS patients. The added diagnostic value of other methodologies and measurements of other APS-associated antibodies are inconsistent. This manuscript describes laboratory parameters useful in the diagnosis of thrombotic APS and will concentrate on the laboratory aspects, clinical significance of assays, and interpretation of aPL results in the diagnosis of thrombotic APS.

The Validation of the 2023 ACR/EULAR Antiphospholipid Syndrome Classification Criteria in a Cohort from Turkey.

Our aim was to validate the performance of the American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) classification criteria for antiphospholipid syndrome (APS), published in 2023, in an APS cohort. A total of 193 patients, 83 with APS (secondary APS, n = 45; primary APS, n = 38) and 110 without APS (systemic lupus erythematosus (SLE), n = 100; others, n = 10), were included in this study. The performance (sensitivity, specificity and area under the curve (AUC)) of the 2023 ACR/EULAR classification criteria for APS was evaluated and the agreement with the revised Sapporo criteria was compared using the kappa test. In our cohort, the sensitivity and specificity of the 2023 ACR/EULAR classification criteria for APS were 73% and 94%, respectively (AUC: 0.836, 95% CI: 0.772-0.899), while the sensitivity and specificity of the revised Sapporo criteria were 66% and 98%, respectively (95% CI: 0.756-0.888). The performance of the two sets of criteria in our cohort was significantly consistent and significant (p < 0.001). When the sensitivity, specificity and ROC curve analysis were performed again by excluding livedo racemosa, the sensitivity of the new criteria in our cohort was 62% and the specificity was 100% (AUC: 0.813, 95% CI: 0.746-0.881). Although the newly published criteria broaden the scope of APS classification by including clinical findings other than thrombosis and obstetric criteria, their sensitivity in our cohort was low. On the other hand, we found that the specificity of the criteria in our cohort reached 100% when livedo findings were excluded.

Dancing with disorder: chorea – an unusual and neglected manifestation of antiphospholipid syndrome

ObjectivesChorea, characterised by involuntary, irregular movements, is a rare neurological manifestation of antiphospholipid syndrome (APS). The specific clinical features remain unclear. This study aimed to summarise the available evidence on...

The 2023 ACR/EULAR antiphospholipid syndrome classification criteria identify patients at high risk of complications.

This study aims to evaluate the utility of the 2023 ACR/EULAR antiphospholipid syndrome (APS) classification criteria in identifying primary APS patients at high risk of complications. In this single-center study, primary APS patients were classified according to both the revised Sapporo criteria and the 2023 ACR/EULAR criteria. The risk of complications was assessed using the adjusted Global Antiphospholipid Syndrome Score (aGAPSS). Forty-five patients (73% females, median age 49years) were included. Thirty-six patients met the 2023 ACR/EULAR criteria, all of whom also fulfilled the revised Sapporo criteria. Additionally, four out of nine patients not meeting the 2023 ACR/EULAR criteria satisfied the revised Sapporo criteria. Agreement rate between the two classification criteria was 91%, with a Cohen's kappa index of 0.66. Patients meeting the 2023 ACR/EULAR criteria had significantly higher aGAPSS scores compared to those who did not (13, 8-13 vs. 3, 0-5; p = 0.005). Furthermore, 55% of patients meeting the 2023 ACR/EULAR criteria were categorized as high risk based on aGAPSS scores, while those not meeting the criteria were predominantly categorized as low risk (77%). Interestingly, patients not meeting the 2023 ACR/EULAR criteria but fulfilling the revised Sapporo criteria had significantly higher aGAPSS scores compared to those not meeting either set of criteria (7, 5-13 vs. 0, 0-1.5; p = 0.015). The 2023 ACR/EULAR criteria effectively identify primary APS patients at increased risk of complications, as indicated by the aGAPSS score. Key Points • Identifying primary APS patients at high risk of complications remains a significant challenge. • The 2023 ACR/EULAR criteria show a correlation with the aGAPSS score, exhibiting the highest correlation with laboratory domains and minimal correlation with clinical domains. • The 2023 ACR/EULAR classification criteria are effective in identifying primary APS patients at high risk of complications.

Development of the 2023 ACR/EULAR Antiphospholipid Syndrome Classification Criteria, Phase III-D Report: Multicriteria Decision Analysis.

The 2023 American College of Rheumatology/EULAR antiphospholipid syndrome (APS) classification criteria development, which aimed to identify patients with high likelihood of APS for research, employed a four-phase methodology. Phase I and II resulted in 27 proposed candidate criteria, which are organized into laboratory and clinical domains. Here, we summarize the last stage of phase III efforts, employing a consensus-based multicriteria decision analysis (MCDA) to weigh candidate criteria and identify an APS classification threshold score. We evaluated 192 unique, international real-world patients referred for "suspected APS" with a wide range of APS manifestations. Using proposed candidate criteria, subcommittee members rank ordered 20 representative patients from highly unlikely to highly likely to have APS. During an in-person meeting, the subcommittee refined definitions and participated in an MCDA exercise to identify relative weights of candidate criteria. Using consensus decisions and pairwise criteria comparisons, 1000Minds software assigned criteria weights, and we rank ordered 192 patients by their additive scores. A consensus-based threshold score for APS classification was set. Premeeting evaluation of 20 representative patients demonstrated variability in APS assessment. MCDA resolved 81 pairwise decisions; relative weights identified domain item hierarchy. After assessing 192 patients by weights and additive scores, the Steering Committee reached consensus that APS classification should require separate clinical and laboratory scores, rather than a single-aggregate score, to ensure high specificity. Using MCDA, candidate criteria preliminary weights were determined. Unlike other disease classification systems using a single-aggregate threshold score, separate clinical and laboratory domain thresholds were incorporated into the new APS classification criteria.

Antiphospholipid Antibody Testing in a Maximum Care Hospital: Method-Dependent Differences.

Background: Antiphospholipid antibody (aPL) testing is critical for the classification of antiphospholipid syndrome. The 2023 ACR/EULAR classification criteria recommend the use of enzyme-linked immunosorbent assays (ELISAs) and specific thresholds for aPL positivity. Since non-ELISA methods are increasingly used, we compared and evaluated ELISA and non-ELISA aPL assays in a real-world maximum care hospital setting. Methods: Between January 2021 and June 2024, anticardiolipin (aCL; IgG and IgM) and anti-beta2 glycoprotein I (aß2GPI; IgG and IgM) antibodies were measured using ELISA (n = 5115) and a chemiluminescence-based automated immunoassay (CLIA) (n = 3820). Results of parallel testing were compared, and associations with clinical and laboratory characteristics were evaluated. Results: A total of 946 samples were tested using ELISA and CLIA in parallel. A total of 136 (14%) specimens were positive for at least one aPL, and 55 (6%) specimens were from patients diagnosed with APS. Among the latter, 47 (85%) and 41 (75%) patients were positive when ELISA- or CLIA-based aPL assays were used, respectively. After applying the >40 units threshold of the new classification criteria, the number of aPL-positive specimens was significantly lower. In the entire cohort, the agreement between ELISA and CLIA aPL assays was acceptable only for aß2GPI IgG; the results from the two methods did not agree for aCL IgG/IgM and aß2GPI IgM. In APS patients, the agreement between ELISA and CLIA aPL assays was acceptable for aß2GPI IgG and IgM but poor for aCL IgG and IgM. Antibody levels in APS patients were significantly higher using CLIA compared to ELISA. Conclusions: The method-dependent discrepancies between ELISA- and CLIA-based aPL assays regarding the quantitative and qualitative results are substantial. Both methods are suitable for APS classification, but the choice of aPL assay may influence the classification, and therefore, aPL results should be interpreted carefully in the clinical context.

Antiphospholipid Syndrome: Insights into Molecular Mechanisms and Clinical Manifestations.

Antiphospholipid syndrome (APS) is a complex systemic autoimmune disorder characterized by a hypercoagulable state, leading to severe vascular thrombosis and obstetric complications. The 2023 ACR/EULAR guidelines have revolutionized the classification and understanding of APS, introducing broader diagnostic criteria that encompass previously overlooked cardiac, renal, and hematologic manifestations. Despite these advancements, diagnosing APS remains particularly challenging in seronegative patients, where traditional tests fail, yet clinical symptoms persist. Emerging non-criteria antiphospholipid antibodies offer promising new diagnostic and management avenues for these patients. Managing APS involves a strategic balance of cardiovascular risk mitigation and long-term anticoagulation therapy, though the use of direct oral anticoagulants remains contentious due to varying efficacy and safety profiles. This article delves into the intricate pathogenesis of APS, explores the latest classification criteria, and evaluates cutting-edge diagnostic tools and therapeutic strategies.

Interaction of antiphospholipid antibodies with endothelial cells in antiphospholipid syndrome.

Antiphospholipid syndrome (APS) is an autoimmune disease with arteriovenous thrombosis and recurrent miscarriages as the main clinical manifestations. Due to the complexity of its mechanisms and the diversity of its manifestations, its diagnosis and treatment remain challenging issues. Antiphospholipid antibodies (aPL) not only serve as crucial "biomarkers" in diagnosing APS but also act as the "culprits" of the disease. Endothelial cells (ECs), as one of the core target cells of aPL, bridge the gap between the molecular level of these antibodies and the tissue and organ level of pathological changes. A more in-depth exploration of the relationship between ECs and the pathogenesis of APS holds the potential for significant advancements in the precise diagnosis, classification, and therapy of APS. Many researchers have highlighted the vital involvement of ECs in APS and the underlying mechanisms governing their functionality. Through extensive in vitro and in vivo experiments, they have identified multiple aPL receptors on the EC membrane and various intracellular pathways. This article furnishes a comprehensive overview and summary of these receptors and signaling pathways, offering prospective targets for APS therapy.

Clinical and Laboratory Diagnosis of Antiphospholipid Syndrome: A Review.

The antiphospholipid syndrome (APS) manifests through venous or arterial thrombosis, with or without pregnancy complication alongside the continuous presence of antiphospholipid antibodies (aPL). APS classification relies on three aPL subtypes: anticardiolipin (aCL), anti-β2-glycoprotein I antibodies (anti-β2GPI), and lupus anticoagulants (LA) antibodies. Given that thrombosis and pregnancy issues are not unique to APS, the precise and reliable identification of aPL forms the basis for diagnosis. Semi-quantitative solid-phase assays identify two antibodies, aCL and anti-β2GPI, while LA detection occurs through various phospholipid-dependent coagulation assays that are based on antibody behaviour. LA, specifically, is conclusively associated with thrombosis, prompting discussions around the serological criteria for APS. Despite advancements in LA detection, the standardisation of all aPL detection assays remains imperative. The combined presence of aCL and anti-β2GPI with thrombosis inconsistently triggers concern. Initial presentations by APS patients commonly exhibit a heightened risk of stroke, miscarriages in the later stages of pregnancy, positive results of LA tests, and widespread thrombosis across multiple organs, often leading to adverse outcomes. Correctly diagnosing this condition is pivotal to avoid unnecessary long-term secondary thromboprophylaxis.

Impact of Inherited Thrombophilia in Women with Obstetric Antiphospholipid Syndrome: A Single-Center Study and Literature Review.

Inherited thrombophilia (IT) has been implicated as a potential causal factor of adverse pregnancy outcomes (APOs), including recurrent miscarriage with and without the presence of antiphospholipid syndrome (APS). The aim of this study was to assess the prevalence and impact of IT on fetal-maternal outcomes and thrombotic risk in women within the spectrum of obstetric APS. Three hundred and twenty-eight women with APS-related obstetric morbidity ever pregnant were included. Of these, 74 met the APS classification criteria, 169 were non-criteria (NC)-APS, and 85 were seronegative (SN)-APS. Patients with other autoimmune diseases were excluded. APOs included early pregnancy loss, fetal death, preeclampsia, abruptio placentae, and preterm birth. Successful pregnancy was defined as the achievement of a live newborn. A literature search was also performed. The mean age of the overall group was 33.9 ± 5.3 years, and the patients were followed up for 35 (11-79) months. During the study period, there were 1332 pregnancies. Nearly 14% of the patients had an associated IT. IT patients more frequently received the standard-of-care (SoC) therapy. The presence of IT was not associated with worse maternal-fetal outcomes in patients treated with SoC treatment. Overall, IT patients had a lower frequency of newborns without treatment, especially those without definite APS. In addition, IT did not increase the risk of thrombosis during pregnancy or the postpartum period. A detailed analysis of the literature review identified only four publications related to our study and did not show conclusive evidence of the impact of IT on patients with obstetric APS. The group of women with APS-related obstetric morbidity and IT who did not receive treatment, especially those without definite APS, had a worse prognosis in terms of a live birth. However, with SoC therapy, the prognosis is similar in those patients without IT. The association of IT with APS does not seem to predispose to the development of thrombosis during pregnancy and/or the postpartum period.

Rethinking antiphospholipid syndrome to guide future management and research.

Antiphospholipid syndrome (APS) consists of thrombotic, non-thrombotic and obstetric clinical manifestations developing in individuals with persistent antiphospholipid antibodies (aPL). Although researchers have made progress in characterizing different clinical phenotypes of aPL-positive people, the current approach to clinical management is still mostly based on a 'one size fits all' strategy, which is derived from the results of a limited number of prospective, controlled studies. With the 2023 publication of the ACR-EULAR APS classification criteria, it is now possible to rethink APS, to lay the groundwork for subphenotyping through novel pathophysiology-informed approaches, and to set a future APS research agenda guided by unmet needs in clinical management.

Assessment and comparison of the 2023 ACR/EULAR APS criteria with the revised Sapporo criteria.

To analyze antiphospholipid antibody (aPL)-positive patients using the 2023 American College of Rheumatology/The European Alliance of Associations for Rheumatology (ACR/EULAR) antiphospholipid syndrome (APS) classification criteria and compare the revised Sapporo criteria and the 2023 ACR/EULAR criteria and evaluate whether the 2023 ACR/EULAR criteria provide added value over the revised Sapporo criteria. In this descriptive study, 94 aPL-positive patients (with or without APS diagnosis) were identified from two hospital-based registries (Gazi and Hacettepe University). Patients were classified into four groups to compare both criteria sets. These four groups are as follows: (1) patients classified with only the revised Sapporo criteria; (2) patients classified with only the 2023 ACR/EULAR APS criteria; (3) patients classified with both two criteria sets; and (4) patients classified with neither two criteria set. Of the 94 patients, 11 were classified with only the revised Sapporo criteria; one with only the 2023 ACR/EULAR APS criteria; 52 with both criteria sets; and 30 with neither set of criteria. For these 94 patients, the operating characteristics of the 2023 ACR/EULAR APS criteria, using the revised Sapporo criteria as the gold standard, the 2023 ACR/EULAR APS entry criteria demonstrated 100% sensitivity, and the 2023 ACR/EULAR APS classification criteria demonstrated 98% specificity and 82.5% sensitivity. The study emphasizes the importance of recognizing differences in clinical manifestations, such as early pregnancy loss without severe preeclampsia (PEC) and/or severe placental insufficiency (PI) and calls for a nuanced discussion on anticardiolipin (aCL) and anti-beta 2-glycoprotein-I (anti-β2GPI) immunoglobulin G (IgG) cutoff values.

Diagnosis and Management of Catastrophic Antiphospholipid Syndrome and the Potential Impact of the 2023 ACR/EULAR Antiphospholipid Syndrome Classification Criteria.

Catastrophic antiphospholipid syndrome (CAPS) is a rare and life-threatening condition characterized by the persistence of antiphospholipid antibodies and occurrence of multiple vascular occlusive events. CAPS currently remains a diagnostic challenge and requires urgent treatment. The diagnosis of CAPS is made difficult by classification criteria used as diagnostic criteria in clinical practice, knowledge derived from retrospective data and case reports, confounding clinical and biological features, and its rapid onset and mortality. The absence of prospective studies of CAPS limits the strength of evidence for guideline treatment protocols. This comprehensive review summarizes the current understanding of the disease, and discusses how the 2023 ACR/EULAR Antiphospholipid Syndrome Classification Criteria impact the definition and therapeutic management of CAPS, which is considered the most severe form of APS. The correct integration of 2023 ACR/EULAR APS classification criteria is poised to facilitate CAPS diagnosis, particularly in critical situations, offering a promising avenue for improved outcomes.

Performance validation of the 2023 American College of Rheumatology/European League Against Rheumatism antiphospholipid syndrome classification criteria in an antiphospholipid syndrome cohort

BackgroundThe 2023 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) antiphospholipid syndrome (APS) classification criteria were developed with higher specificity but lower sensitivity compared with the 2006 Sydney revised classification criteria. ObjectivesTo validate the performance of the 2023 ACR/EULAR APS classification criteria in a large Chinese APS cohort. MethodsThis was a single-center cohort study. Inclusion criteria aligned with the entry criteria of 2023 criteria. APS classification by “expert consensus panel” served as the gold standard. Sensitivity and specificity were compared between the 2023 and 2006 criteria. ResultsA total of 526 patients with a mean age of 38.55 ± 12.67 years were enrolled, of whom 366 (69.58%) were female and 182 (34.60%) had systemic lupus erythematosus (SLE). Among them, 407 (77.38%) patients were classified as APS by experts. The 2023 criteria demonstrated higher overall specificity than the 2006 criteria (0.983 vs 0.950), while sensitivity was relatively lower (0.818 vs 0.853). The sensitivity of the 2023 criteria improved for patients with SLE (0.860 vs 0.825), microvascular manifestations (0.867 vs 0.786), cardiac valve disease (0.903 vs 0.774), and thrombocytopenia (0.811 vs 0.790). Reduced sensitivity of the 2023 criteria was linked to the omission of certain microvascular manifestations, a stricter definition of pregnancy morbidity, and the exclusion of isolated thrombocytopenia and isolated IgM isotype antiphospholipid antibodies from meeting clinical and laboratory criteria, respectively. ConclusionThe 2023 criteria offer higher overall specificity and improved sensitivity in specific patient subsets, such as those with SLE, microvascular manifestations, cardiac valve disease, and thrombocytopenia when compared with the 2006 criteria.

Antiphospholipid Syndrome: To Classify or Not to Classify?

Antiphospholipid syndrome (APS) is a systemic autoimmune disorder resulting in thrombosis, microvascular disease, morbidity in pregnancy, and/or non-thrombotic manifestations. The recently introduced 2023 American College of Rheumatology (ACR) and European Alliance of Associations for Rheumatology (EULAR) APS classification criteria, with significantly higher specificity compared to the revised Sapporo criteria, now reflect the current thinking about APS and provide a new foundation for future APS research. The purpose of this short commentary is to discuss the appropriate circumstances under which the 2023 ACR/EULAR classification criteria could be used and to demonstrate how the new criteria can be applied to simple case scenarios.

Quantification of Antiphospholipid Antibodies: The Importance of Using an Appropriate Methodology for Each Clinical Profile.

The presence of antiphospholipid antibodies (aPLs) is associated with antiphospholipid syndrome (APS), characterized by thrombosis and obstetric morbidity. aPLs included in APS classification criteria are lupus anticoagulant, anti-cardiolipin and anti-beta-2-glycoprotein-I of IgG or IgM isotypes. Enzyme-linked immunosorbent assay is the most used diagnostic technique to determine aPLs. Recently, new automated technologies mainly based in antigen-coated beads have been developed. The aim is to compare a fluorescence enzyme immunoassay (M1) and an antigen-coated bead assay (M2) in obstetric and thrombotic APS patients. All samples from the first 1020 patients received in the Immune Service Laboratory (Hospital 12 de Octubre) during the recruitment period, without exclusions, were analysed for aPLs. The weighted kappa for both methods in all the patients was 0.39 (0.30-0.47). Agreement increased to 0.56 (0.38-0.73) in patients with autoimmune disease. Sensitivity and specificity obtained for M1 were 17.1% and 89.3%, respectively, and 12.7% and 91.4% for M2. The sensibility and specificity of IgG isotypes were higher than the IgM ones. Regarding obstetric patients, M1 obtained significant diagnostic performance and had more sensitivity 23.75 (14.95-34.58) compared to M2 12.50 (6.16-21.79). In conclusion, clinical suspicion-based method selection for aPLs should be considered. To identify obstetric APS patients, solid phase methods remain more preferable.

Antiphospholipid Antibodies and Vascular Thrombosis in Patients with Severe Forms of COVID-19.

Antiphospholipid antibodies (aPLA) are a laboratory criterion for the classification of antiphospholipid syndrome (APS) and are known to cause clinical symptoms such as vascular thrombosis or obstetric complications. It is suggested that aPLA may be associated with thromboembolism in severe COVID-19 cases. Therefore, we aimed to combine clinical data with laboratory findings of aPLA at four time points (admission, worsening, discharge, and 3-month follow-up) in patients hospitalized with COVID-19 pneumonia. In 111 patients with COVID-19 pneumonia, current and past history of thrombosis and pregnancy complications were recorded. Nine types of aPLA were determined at four time points: anticardiolipin (aCL), anti-β2-glycoprotein I (anti- β2GPI), and antiphosphatidylserine/prothrombin (aPS/PT) of the IgM, IgG, or IgA isotypes. During hospitalization, seven patients died, three of them due to pulmonary artery thromboembolism (none were aPLA positive). Only one of the five who developed pulmonary artery thrombosis was aPLA positive. Out of 9/101 patients with a history of thrombosis, five had arterial thrombosis and none were aPLA positive at admission and follow-up; four had venous thrombosis, and one was aPLA positive at all time points (newly diagnosed APS). Of these 9/101 patients, 55.6% were transiently aPLA positive at discharge only, compared to 26.1% without a history of thrombosis (p = 0.041). Patients with severe forms of COVID-19 and positive aPLA should receive the same dose and anticoagulant medication regimen as those with negative aPLA because those antibodies are mostly transiently positive and not linked to thrombosis and fatal outcomes.

Proteomic Profiling of Different Antiphospholipid Antibody-Positive Phenotypes: Results from Antiphospholipid Syndrome Alliance for Clinical Trials and International Networking (APS ACTION) Registry

Background. Antiphospholipid syndrome (APS) is an autoimmune disease with thrombotic and obstetric complications arising via a model of immunothrombosis. Patients may present with a spectrum of phenotypes, including thrombotic (tAPS), obstetric (oAPS), or catastrophic/microvascular APS (C/MAPS), while others may have antiphospholipid antibodies (aPL) without disease manifestations. The mechanisms underlying the development of these diverse phenotypes remain uncertain. Proteomic profiling was used in other thrombotic and microvascular disorders to highlight potential mechanisms of disease pathogenesis and may have a role in understanding the pathophysiology of APS. We performed multiplex plasma proteomic profiling in aPL-positive patients with different clinical phenotypes to gain a greater understanding of potential immunothrombotic mechanisms in the pathogenesis of APS. Methods. We utilized samples from APS ACTION Registry. The inclusion criteria were positive aPL per Updated Sapporo Classification Criteria tested within one year prior to the enrollment. Multiplex proteomic profiling measuring approximately 7,000 unique proteins (SomaLogic; Boulder, CO, USA) was performed on 40 primary aPL-positive patient plasma samples (10 each of tAPS with/without oAPS, oAPS only, C/MAPS, and positive aPL without APS classification), and 10 of healthy controls. Differentially abundant proteins among all phenotypic groups and in pairwise comparisons were determined by applying ANOVA and t-tests to log-normalized data, respectively, with p-values &amp;lt;0.05 considered statistically significant (Qlucore Omics Explorer, Lund, Sweden). Tests were adjusted for false discovery (q&amp;lt;0.1) to minimize the likelihood of false positives. Pathway enrichment analysis was performed using Metascape (https://metascape.org) and Ingenuity IPA (Qiagen, Venlo, Netherlands) platforms. Results. The median age of patients was 48 years; 30% were men, 70% had triple aPL-positivity, and no one had a concurrent diagnosis of lupus. A set of concordant and differentially abundant proteins clustered patients with 4 APS clinical phenotypes and controls (Figure A) with a high statistical significance (p&amp;lt;0.0007) and a high false discovery confidence (q&amp;lt;0.05). Proteins in the identified set belonged to several highly enriched pathways such as neutrophil degranulation (p&amp;lt;10 -10), humoral immune response (p&amp;lt;10 -9), coagulation (p&amp;lt;10 -6), and alternative complement (p&amp;lt;10 -5) [data not shown]. Pathway enrichment analysis of protein sets identified in pairwise comparisons of APS phenotypes (aPL vs C/MAPS, aPL vs tAPS, tAPS vs C/MAPS) revealed involvement of several common pathways associated with inflammation, collagen and fibroblast signaling, cellular and cytoskeletal activation, humoral immune response, myeloid and effector cell differentiation and recruitment, and immunothrombosis such as Pathogen-Induced Cytokine Storm, Neutrophil Extracellular Trap (NET), and collagen-induced platelet-activating GP6 signaling (Figure B). For several pathways, the measure of activation related to increased or predicted to be increased proteins annotated within a particular pathway positively correlated with the clinical “distance” between APS subtypes, from the most clinically related C/MAPS vs tAPS to the most distant aPL vs C/MAPS suggesting an “evolution” from one phenotype to a more severe in terms of activation of specific pathways. Specifically notable is the higher activation of the NET signaling pathway in the aPL than in C/MAPS phenotype suggesting that the presence of aPL antibodies activates this immunothrombotic pathway. Conclusions. Plasma proteome of APS subtypes is characterized by alteration in several cellular processes, particularly receptor signaling, signal transduction, regulation of cellular differentiation, neutrophil, complement, coagulation and cytokine activation notable in all individuals with aPL-positivity. Pathways activated in the non-thrombotic (aPL) phenotype and escalating activation of several pathways from non-thrombotic to the most thrombotic (C/MAPS) phenotype provide important data for the understanding of APS pathogenesis and informing the model of APS-related immunothrombosis.

Do Patients with Antiphospholipid Syndrome Have More Significant Venous Thromboembolic Clot Burden?: A Single-Center Retrospective Analysis

Background: Antiphospholipid syndrome (APS) is a prothrombotic condition defined by arterial or venous thrombotic events and/or obstetrical morbidity in the presence of persistently positive antiphospholipid antibodies (aPL). Venous thromboembolic disease (VTE), comprised mostly of deep vein thrombosis (DVT) and pulmonary embolism (PE), is the initial presenting clinical manifestation in approximately 35% of APS diagnoses. VTE is a heterogenous disease and can present with varying degrees of clot burden. Lower extremity DVT can present with thrombus in the iliofemoral, femoropopliteal, and/or distal calf veins; pulmonary embolism can present with thrombus in the main pulmonary arteries, lobar branches, segmental, and/or subsegmental branches. In both DVT and PE, more proximal clot burden portends higher morbidity and mortality. While VTE is a commonly encountered clinical presentation, the decision regarding whom to test for APS is often challenging. Current guidelines recommend that clinicians consider testing for APS in patients with unexplained venous or arterial thrombotic events, especially young patients, or when a patient has one or more specific adverse outcomes related to pregnancy. To date, no data exist to suggest that patients with APS are more likely to present with more extensive venous thromboembolic clot burden as compared to patients without APS. Purpose: To assess clot burden in patients with a co-diagnosis of VTE and APS in comparison to patients with VTE without APS to determine if clot burden should be considered when deciding whom to test for APS. Methods: This retrospective cohort study included adult patients with a history of VTE who had also been tested for APS within a multihospital academic healthcare system from December 1, 2019 through January 31, 2022. All patients in the study had a history of VTE and were considered to be positive for APS if they had persistently positive aPL and/or lupus anticoagulant in accordance with the revised Sapporo APS Classification Criteria. Patients were excluded if they had confounding provoking risk factors for thrombosis. Patients were stratified as APS and non-APS. Significant clot burden was defined as PE involving the main and/or lobar pulmonary arteries or DVT involving the iliofemoral veins. Assessment of clot burden was performed by review of radiology reports of the sentinel clotting event.Patients were further stratified based on age, BMI, insurance status, severity of APS (triple-positive APS versus non-triple-positive APS), and type of APS (primary versus secondary). Exploratory analysis of the patient groups was performed. Summary statistics are presented as percentages for categorical data and median with interquartile range for quantitative data. Chi square test was used to compare percentages and t-test was used to compare means. Univariate and multivariate regression models were used to analyze the predictors of significant clot burden. Results: We identified 748 patients with a history of VTE who had also been tested for APS. The study population was comprised of 53.1% females with a median age of 59 (IQR 46-69). A majority of the patients were Caucasian (85%). APS was detected in 75 (10%) patients. Significant clot burden was present in 29 (38.7%) APS patients and 269 (40.0%) non-APS patients (OR 0.95, 95% CI 0.58-1.56; P = 0.85). On univariate analysis, age (OR 1.01, 95% CI 1.00-1.02; P = 0.02) and being uninsured (OR 9.2, 95% CI 1.10-76.10; P = 0.04) were associated with more significant clot burden. No predictors for significant clot burden were found on multivariable analysis. Triple positive APS (OR 0.83, 95% CI 0.16-4.21; P = 0.82) and primary APS (OR 0.72, 95% CI 0.15-3.45; P = 0.68) were not associated with more significant clot burden. Conclusions: In this retrospective cohort of 748 patients with a history of VTE, the presence of antiphospholipid syndrome was not associated with more significant VTE clot burden as compared to non-APS patients. Based on these data, VTE clot burden may not be a reliable predictor for the presence of APS. Study limitations include selection bias, retrospective design, and lack of precise volumetric measurement of blood clots.