The presence of IgG antibodies against beta2-glycoprotein I predicts the risk of thrombosis in patients with the lupus anticoagulant

Application of the thrombin generation assay in patients with antiphospholipid syndrome: A systematic review of the literature

Background

The antiphospholipid syndrome (APS) is classified by the presence of antiphospholipid antibodies (aPL) and thrombotic and/or adverse obstetric outcomes. The diagnosis and risk assessment of APS is challenging. This systematic review investigated if the thrombin generation (TG) assay could be helpful for APS diagnosis and risk assessment.

Methods

A systemic review was performed by searching two databases (MEDLINE and Embase) until March 31, 2022, using a search strategy with two concepts: APS and TG, and related keywords. Two reviewers independently screened the articles based on predefined inclusion and exclusion criteria. Data extraction and quality assessment with the Newcastle-Ottawa Scale (NOS) were performed independently. Synthesis Without Meta-analysis guidelines were followed for data synthesis reporting.

Results

Fourteen studies with 677 APS and 1,349 control subjects were included with variable quality according to the NOS. Twelve studies measured TG via the calibrated automated thrombogram (CAT) method using a fluorogenic substrate, whereas two used a chromogenic substrate-based TG assay. One study compared the CAT assay to the fully-automated ST Genesia® (Stago, France). Two studies initiated TG using platelet-rich plasma, whereas the rest of the studies used platelet-poor plasma. Resistance to activated protein C (aPC) was examined in ten studies. They reported a significant increase in aPC-resistance in APS patients compared to healthy controls, aPL-carriers, and thrombotic controls. Based on two studies, the prevalence of aPC-resistance was higher in APS patients compared to healthy controls and thrombotic controls with odds ratios of 5.9 and 6.8–12.8, respectively (p < 0.05). In contrast, no significant difference in aPC-resistance was found between APS patients and autoimmune disease controls. Furthermore, 7/14 studies reported TG-parameters including peak height, endogenous thrombin potential, lag time, and time to peak, but these outcomes were highly variable between studies. Furthermore, TG methodology between studies differed greatly, impacting the comparability of the studies.

Conclusion

aPC-resistance measured with TG was increased in APS patients compared to healthy and thrombotic controls, but the diagnostic and prognostic value is unclear compared to current diagnostic strategies. Studies of other TG-parameters were heterogeneous and more research is needed to identify their potential added value in APS diagnosis.

Systematic Review Registration

https://www.PROSPERO/, identifier: CRD42022308363

A systematic review of the association between anti-β-2 glycoprotein I antibodies and APS manifestations

Anti-β-2 glycoprotein I antibodies (anti-B2GPI) are often cited as the major pathogenically relevant antibody in antiphospholipid syndrome (APS), but it is unclear if there is clinical evidence to support this theory. We performed a systematic review to determine if immunoglobulin G anti-B2GPI positivity was independently associated with thrombotic and/or obstetric manifestations of APS. We searched MEDLINE, EMBASE, The Cochrane Library, and clinicaltrials.gov electronic databases through April 2020 for prospective studies that met prespecified design criteria. Of 4758 articles identified through computer-assisted search, 4 studies examining obstetric outcomes and 2 studies examining thrombotic outcomes were included for qualitative assessment. The presence of anti-B2GPI had only a weak independent association with thrombosis and was, at best, inconsistently associated with obstetric complications. A quantitative assessment could not be performed because of study heterogeneity. The overall quality of the evidence was very low. Although anti-B2GPI are commonly thought to mediate APS manifestations, clinical evidence is lacking with very low-quality data to support a weak association with thrombosis.

Recommendations of the Spanish Rheumatology Society for Primary Antiphospholipid Syndrome. Part I: Diagnosis, Evaluation and Treatment

OBJECTIVE

The difficulty in diagnosis and the spectrum of clinical manifestations that can determine the choice of treatment for primary antiphospholipid syndrome (APS) has fostered the development of recommendations by the Spanish Society of Rheumatology (SER), based on the best possible evidence. These recommendations can serve as a reference for rheumatologists and other specialists involved in the management of APS.

METHODS

A panel of four rheumatologists, a gynaecologist and a haematologist with expertise in APS was created, previously selected by the SER through an open call or based on professional merits. The stages of the work were: identification of the key areas for drafting the document, analysis and synthesis of the scientific evidence (using the Scottish Intercollegiate Guidelines Network [SIGN] levels of evidence) and formulation of recommendations based on this evidence and formal assessment or reasoned judgement techniques (consensus techniques).

RESULTS

46 recommendations were drawn up, addressing five main areas: diagnosis and evaluation, measurement of primary thromboprophylaxis, treatment for APS or secondary thromboprophylaxis, treatment for obstetric APS and special situations. These recommendations also include the role of novel oral anticoagulants, the problem of recurrences or the key risk factors identified in these subjects. This document reflects the first 21, referring to the areas of: diagnosis, evaluation and treatment of primary APS. The document provides a table of recommendations and treatment algorithms.

CONCLUSIONS

An update of the SER recommendations on APS is presented. This document corresponds to partI, related to diagnosis, evaluation and treatment. These recommendations are considered tools for decision-making for clinicians, taking into consideration both the decision of the physician experienced in APS and the patient. A partII has also been prepared, which addresses aspects related to obstetric SAF and special situations.

What is the appropriate anticoagulation strategy for thrombotic antiphospholipid syndrome?

Antiphospholipid syndrome (APS) is an autoimmune prothrombotic disorder mediated by a heterogeneous group of autoantibodies collectively known as antiphospholipid antibodies (aPL). They include lupus anticoagulant (LA), IgG and IgM anticardiolipin antibodies (aCL) and anti-β2-glycoprotein I (anti-β2GPI) antibodies. It has been shown that those patients with all three aPL (triple positive) are at highest risk of both a first thrombotic event and of a recurrence, despite anticoagulation. In response to publication of a meta-analysis and a randomised controlled trial assessing the safety and efficacy of rivaroxaban versus warfarin in triple-positive APS with venous and/or arterial thrombosis, the Medicines and Healthcare Products Regulatory Agency (MHRA) and European Medicines Agency (EMA) issued recommendations that direct-acting oral anticoagulant (DOACs) should not be used for secondary prevention of thrombosis in all APS patients (although they did draw specific attention to the high risk of triple-positive patients). As there is less evidence for patients with single- or dual-positive patients with APS, this may be an over-interpretation of the data. In this review, we explore the available evidence on safety and efficacy of DOACs in thrombotic APS, the problem of detecting LA while on DOAC, and provide some practical guidance for managing this problem.

The (non-)sense of detecting anti-cardiolipin and anti-β2glycoprotein I IgM antibodies in the antiphospholipid syndrome

BACKGROUND

The antiphospholipid syndrome (APS) is characterized by thrombosis and/or pregnancy morbidity with the persistent presence of lupus anticoagulant (LAC), anti-cardiolipin (aCL) and/or anti-β2glycoprotein I (aβ2GPI) antibodies of the immunoglobulin G/immunoglobulin M (IgG/IgM) isotype. However, the role of aCL and aβ2GPI IgM as a serologic marker in APS is debated.

OBJECTIVES

We aimed to assess the diagnostic and clinical value of IgM antiphospholipid antibodies (aPL) in APS within the classification criteria.

PATIENTS/METHODS

Our multicenter study comprised 1008 patients, including APS patients and controls. Anti-CL and aβ2GPI IgG and IgM antibodies were detected with four commercially available solid phase assays.

RESULTS

Positivity for aCL and/or aβ2GPI antibodies was significantly correlated with thrombosis and pregnancy morbidity, independent of the isotype and solid phase assay. Higher odds ratios were obtained for IgG compared to IgM positivity. Isolated IgM was rare in thrombotic APS, but more frequent in obstetric APS, ranging from 3.5% to 5.4% and 5.7% to 12.3%, respectively, dependent on the solid phase assay. In a multivariate logistic regression analysis of aPL, IgM positivity was found to be associated with pregnancy morbidity. However, detection of IgM was not independently associated with thrombosis. Combined positivity for LAC, IgG, and IgM was highly associated with thrombosis and pregnancy morbidity.

CONCLUSIONS

Our data support testing for aCL and aβ2GPI IgM in women suspected of obstetric APS. However, no added value was found for testing IgM in patients suspected of thrombotic APS. Still, IgM aPL might be useful as a second-line test to improve thrombotic risk stratification.

The role of beta-2-glycoprotein I in health and disease associating structure with function: More than just APS

Beta-2-Glycoprotein I (β2GPI) plays a number of essential roles throughout the body. β2GPI, C-reactive protein and thrombomodulin are the only three proteins that possess the dual capability to up and down regulate the complement and coagulation systems depending upon external stimulus. Clinically, β2GPI is the primary antigen in the autoimmune condition antiphospholipid syndrome (APS), which is typically characterised by pregnancy morbidity and vascular thrombosis. This protein is also capable of adopting at least two distinct structural forms, but it has been argued that several other intermediate forms may exist. Thus, β2GPI is a unique protein with a key role in haemostasis, homeostasis and immunity. In this review, we examine the genetics, structure and function of β2GPI in the body and how these factors may influence its contribution to disease pathogenesis. We also consider the clinical implications of β2GPI in the diagnosis of APS and as a potentially novel therapeutic target.

Rivaroxaban vs warfarin in high-risk patients with antiphospholipid syndrome

Publisher's Note: There is a Blood Commentary on this article in this issue.

Thrombotic risk assessment and analytical performance of the chemiluminescent analyzer IDS-iSYS for the detection of anti-cardiolipin and anti-beta 2 glycoprotein I autoantibodies

Patients with antiphospholipid antibodies (APLA) are predisposed to develop thrombosis, however the standardization of anti-cardiolipin (aCL) and anti-beta 2 glycoprotein I (β2-GPI) Ab assays are challenging. Therefore we decided to test the performance of a new chemiluminescent assay (CLIA), and assayed aCL and aβ2-GPI IgG/M in serum from 120 healthy individuals, 108 patients with idiopathic venous thrombosis, 78 patients with antiphospholipid syndrome (APS), and 64 non-thrombotic APLA-carriers using CLIA IDS-iSYS. Very good (aCL/aβ2-GPI IgG) to moderate (aCL/aβ2-GPI IgM) agreement with a commercial and an in house ELISA assay were observed and, in particular, CLIA demonstrated the highest sensitivity in aβ2-GPI IgG detection. Finally, aCL/aβ2-GPI Ab capacity to predict the thrombotic risk was tested showing for CLIA a significant odds ratio (OR) when considering double positivity for aCL/aβ2-GPI IgG, aCL IgG at high levels, and aβ2-GPI IgG at high levels. In conclusion, CLIA improves aβ2-GPI IgG detection and thrombotic risk assessment.

Antiphospholipid syndrome characteristics and adverse pregnancy outcomes after 20 weeks of pregnancy

OBJECTIVE

To assess outcomes after 20 weeks of pregnancy according to autoantibody profile and clinical presentation of maternal antiphospholipid syndrome (APS).

METHODS

The present retrospective cohort analysis included women diagnosed with APS at a tertiary medical center in Israel between January 1, 2012, and December 31, 2016. Anticardiolipin antibodies, anti-β2-glycoprotein antibodies, and lupus anticoagulant were assessed. Participants were stratified by type of APS (obstetric vs thrombotic), antibody profile, and antibody titer (low vs high). Primary composite outcomes were rated as severe (stillbirth, fetal growth restriction at <34 weeks, severe pre-eclampsia, or delivery at <32 weeks) and mild (stillbirth, any fetal growth restriction, any pre-eclampsia, or delivery at <34 weeks).

RESULTS

A total of 99 women were included in the analysis. The primary composite outcomes were similar regardless of stratification. Lupus anticoagulant positivity was associated with delivery before 37 weeks. When compared with low antibody titer, high antibody titer was associated delivery at or before 32 weeks (P=0.045) and 34 weeks (P=0.029).

CONCLUSION

High antibody titer might be associated with an increased risk of severe prematurity among pregnant women with APS.

Effects of anti-β2GPI antibodies on VWF release from human umbilical vein endothelial cells and ADAMTS13 activity

BACKGROUND

Antiphospholipid syndrome (APS) is characterized by recurrent thromboembolic events in the setting of pathologic autoantibodies, some of which are directed to β2-Glycoprotein 1 (β2GPI). The mechanisms of thrombosis in APS appear to be multifactorial and likely include a component of endothelial activation. Among other things, activated endothelium secretes von Willebrand factor, a hemostatic protein that in excess can increase the risk of thrombosis.

OBJECTIVE

We hypothesized that anti-β2GPI antibodies could regulate the release and modulation of VWF from endothelial cells.

PATIENTS/METHODS

Isolated anti-β2GPI antibodies from patients with APS were assayed for their ability to induced VWF release from HUVECs and modulate the effects of ADAMTS13 in a shear-dependent assay.

RESULTS

We observed that anti-β2GPI antibodies from some patients with APS induced VWF release from human endothelial cells but did not induce formation of cell-anchored VWF-platelet strings. Finally, we also determined that one of the Anti-β2GPI antibodies tested can inhibit the function of ADAMTS13, the main modulator of extracellular VWF.

CONCLUSIONS

These results suggest that VWF and ADAMTS13 may play a role in the prothrombotic phenotype of APS.

Role of anti-domain 1-β2 glycoprotein I antibodies in the diagnosis and risk stratification of antiphospholipid syndrome

Essentials Antibodies to domain 1 of β2 glycoprotein I (aD1) are a subset of antiphospholipid antibodies. We evaluated the added diagnostic value of an automated aD1 assay in antiphospholipid syndrome. AD1 IgG correctly classifies patients at risk for thrombosis. Agreement between aD1 and aβ2GPI IgG is high, limiting the added value of aD1 in our setting. Click to hear Professor de Groot's perspective on new mechanistic understanding in antiphospholipid syndrome

SUMMARY

Background Laboratory diagnosis of antiphospholipid syndrome (APS) includes lupus anticoagulant (LAC), anticardiolipin (aCL) or anti-β2 glycoprotein I (aβ2 GPI) antibodies. Antibodies targeting domain 1 of β2 GPI (aD1) constitute a pathogenic subset of autoantibodies. Objectives In this cohort study, we determined the clinical performance characteristics, additional diagnostic value and the contribution to APS risk stratification of an automated aD1 assay. Patients/Methods LAC, aCL, aβ2 GPI and aD1 IgG were measured in 101 APS patients, 123 patients with autoimmune disorders, 82 diseased controls and 120 healthy controls. aD1 antibodies were detected by QUANTA Flash(®) Beta2GPI-Domain 1 chemiluminescence immunoassay. Results With a cut-off value of 20.0 CU, the aD1 IgG assay identifies APS patients in a clinically affected patient cohort with a sensitivity of 53.5% and specificity of 98.8%. It implied a high odds ratio (OR) for clinical events (OR, 17.0; 95% confidence interval [CI], 7.1-40.5). aD1 IgG did not add diagnostic value to the formal aPL panel because aβ2 GPI IgG was nearly as specific but more sensitive for APS (sensitivity 56.4%) with a higher OR for clinical events (36.2; 95% CI, 11.1-117.9). High aD1 titers identify triple-positive patients and patients with thrombosis in a β2 GPI-dependent LAC-positive population. Agreement between aD1 IgG and aβ2 GPI IgG was high (positive and negative agreement 91.7% and 98.4%, respectively). Conclusion Detection of aD1 IgG correctly classifies patients at risk of thrombosis. However, the contribution of aD1 IgG to APS diagnosis and risk stratification depends upon the solid phase assays used for aCL and aβ2 GPI detection.

IgG/IgM antiphospholipid antibodies present in the classification criteria for the antiphospholipid syndrome: a critical review of their association with thrombosis

Essentials The clinical value of IgM antibodies in thrombotic antiphospholipid syndrome (APS) is debated. By review of literature, we reconsidered the clinical value of IgM antibodies in thrombotic APS. More significant correlations with thrombosis were found for the IgG compared to IgM isotype. Unavailability of paired IgG/IgM results hampers evaluating the added value of IgM positivity. Click to hear Dr de Groot's perspective on antiphospholipid syndrome

SUMMARY

Background Despite the update of the classification criteria for the antiphospholipid syndrome (APS), difficulties persist in the identification of patients at risk for thrombosis. Current guidelines include assays detecting IgG/IgM anti-β2 -glycoprotein I and anti-cardiolipin antibodies, although the relevance of IgM antibodies has been debated. Objectives Through a review of the literature from 2001 to 2014, we aimed to formally establish the thrombotic risk stratification potential of IgM as compared with IgG anti-phospholipid antibodies (aPLs). Patients/methods One thousand two hundred and twenty-eight articles were selected by a computer-assisted search of the literature. Of the 177 studies that met our inclusion criteria, the clinical value of IgG/IgM aPLs was established through analysis of odds ratios for thrombosis or percentage of positives in the thrombotic population. Results/conclusions We clearly found more significant correlations with thrombosis for the IgG than for the IgM isotype. Nonetheless, in a minority of studies, significant associations with thrombosis were found for IgM but not IgG antibodies. The unavailability of paired results of IgG and IgM for each separate patient hampers evaluation of the added value of isolated IgM positivity. To fully take advantage of results obtained by future studies, we strongly encourage scientists to provide all studied information per patient. We planned a large multicenter study to investigate clinical associations of isolated/combined positivity for criteria/non-criteria aPLs. Importantly, because of the presence of non-pathogenic aPLs, quantitative assays are characterized by a high false-positivity rate. Optimization of functional assays, such as thrombin generation measuring the whole scheme of coagulation, may help to reduce APS-related morbidity and mortality.

Evaluation of three fully automated immunoassay systems for detection of IgA anti-beta 2-glycoprotein I antibodies

INTRODUCTION

In recent years, we have been witnessing increased clinical interest in the determination of IgA anti-beta 2-glycoprotein I (aB2GPI) antibodies as well as increased demand for this test. Some ELISA-based diagnostic systems for IgA aB2GPI antibodies detection are suboptimal to detect it. The aim of our study was to determine whether the diagnostic yield of modern detection systems based on automatic platforms to measure IgA aB2GPI is equivalent to that of the well-optimized ELISA-based assays.

METHODS

In total, 130 patients were analyzed for IgA aB2GPI by three fully automated immunoassays using an ELISA-based assay as reference. The three systems were also analyzed for IgG aB2GPI with 58 patients.

RESULTS

System 1 was able to detect IgA aB2GPI with good sensitivity and kappa index (99% and 0.72, respectively). The other two systems had also poor sensitivity (20% and 15%) and kappa index (0.10 and 0.07), respectively. On the other hand, kappa index for IgG aB2GPI was >0.89 in the three systems.

CONCLUSION

Some analytical methods to detect IgA aB2GPI are suboptimal as well as some ELISA-based diagnostic systems. It is important that the scientific community work to standardize analytical methods to determine IgA aB2GPI antibodies.

Specificities of Platelet Autoantibodies and Platelet Activation in Lupus Anticoagulant Patients: A Relation to their History of Thromboembolic Disease

Lupus anticoagulants (LA) prolong in vitro phospholipid-dependent coagulation tests, but are associated with thromboembolic disease (TE). However, a subgroup of individuals with LA has no TE, and it is therefore desirable to distinguish those at risk for TE from those without. Whether platelets have a primary role in the development of TE is not clear yet. We determined platelet autoantibodies to identify a specific platelet target which is associated with platelet activation in 97 patients with a long history of detectable LA, 65 patients with TE (LA/TE+), and 32 individuals without TE (LA/TE+). Thrombocytopenia was more common in the LA/TE- than in the LA/TE+ group ( P &lt; 0.05). Both groups had platelet antibodies, but the frequency of antibodies was lower in LA/TE+ than LA/TE- patients ( P &lt; 0.01), who had higher antibody titres against glycoprotein IIb/IIIa and glycoprotein Ib/IX ( P &lt; 0.05). Also, their platelets were more activated, as determined by PAC-1 binding ( P &lt; 0.01). These differences were also noted if patients with arterial thrombosis were evaluated separately. These findings in LA/TE- individuals were similar to those in patients with chronic autoimmune thrombocytopenia. However, there was no autoantibody target identifiable to distinguish between LA/TE- from LA-TE+ individuals. We therefore conclude that the presence of platelet antibodies, even if associated with platelet activation, is not sufficient to dispose LA patients to thromboembolic disease.

Adrenal gland abnormalities detected by magnetic resonance imaging in patients with antiphospholipid syndrome

BACKGROUND

Adrenal infarction is a rare complication of antiphospholipid syndrome (APS).

OBJECTIVES

The purpose of the current study is to detect and study the magnetic resonance imaging (MRI) findings of adrenal glands in APS patients.

MATERIALS AND METHODS

In a cross-sectional study, the data of 20 patients with primary or secondary APS were compared to 20 SLE patients without antiphospholipid antibody (aPL) syndrome (controls). MRI of the abdomen showing the adrenal glands was performed.

RESULTS

Of the patients, 80% were females with a mean age 32.45 ± 9.93 years, and mean disease duration of 46.65 ± 58.71 months. Adrenal gland abnormalities in the MRI study were detected in 35 % of APS patients vs. no abnormalities detected in the SLE controls. Adrenal gland enlargement was found in all patients (35 %). Capsular enhancement (infarction or hemorrhagic infarction) was found in 5 patients, increased stranding of the surrounding fat planes (inflammatory process) in 4 patients and increased signal on T1WI and T2WI (hemorrhage) in 3 patients. In patients with adrenal gland involvement, 71.4 % had triple aPL positivity compared to 23.1 % in patients with normal adrenal findings (p = 0.04).

CONCLUSIONS

Adrenal gland abnormalities on MRI were detected in 35 % of the APS patients (whether primary or secondary); thus, increased focus on management is needed. This percentage is not small and needs to be focused on in terms of management.

The Significance of Anti-Beta-2-Glycoprotein I Antibodies in Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is a thrombophilic disorder that classically presents with vascular thrombosis and/or obstetric complications. APS is associated with antiphospholipid antibodies: a heterogeneous group of autoantibodies that are directed against membrane phospholipids in complex with phospholipid-binding proteins. Beta-2-glycoprotein I (B2GPI) binds anionic phospholipids and is considered to be the predominant antigen in APS and antibodies against B2GPI (anti-B2GPI) are recognised in the laboratory criteria for APS diagnosis. This review focuses on the part played by anti-B2GPI in the pathogenesis of APS, their associations with different clinical phenotypes of the disorder and new avenues for refining the diagnostic potential of anti-B2GPI testing.

Efficacy and safety of rivaroxaban vs warfarin in high-risk patients with antiphospholipid syndrome: Rationale and design of the Trial on Rivaroxaban in AntiPhospholipid Syndrome (TRAPS) trial

Background

New oral anticoagulants may simplify long-term therapy in conditions requiring anticoagulation. Rivaroxaban is a direct factor Xa inhibitor that has been extensively studied and is now approved for the prevention and therapy of a number of thromboembolic conditions.

Objective and methods

This is a multicentre, randomized, open-label, study that will evaluate if Rivaroxaban 20 mg od (or 15 mg od in patients with moderate renal insufficiency) is non-inferior to warfarin (INR target 2.5), for the prevention of thromboembolic events, major bleeding and death in high risk (triple positive) patients with antiphospholipid syndrome. Secondary endpoints will assess the incidence of any individual component of the composite end point. An external adjudication committee will evaluate all suspected outcome events. This will be a unique trial, as it will enrol the biggest homogenous cohort of high risk APS individuals.

Conclusion

The methods and the study design should be appropriate to achieve study results that are both scientifically valid and relevant to clinical practice.

Persistent antiphospholipid antibody (aPL) in asymptomatic carriers as a risk factor for future thrombotic events: a nationwide prospective study

Objectives

The long-term prognosis of individuals fulfilling the laboratory criteria, but not clinical criteria, of antiphospholipid syndrome (APS) has not been widely investigated. The primary aim of this study was to evaluate the incidence of first thrombotic event (deep venous thrombosis (DVT), pulmonary embolism (PE), myocardial infarction (MI), stroke or transient ischaemic attack (TIA) in a nationwide antiphospholipid antibody (aPL) carrier cohort.

Design

We conducted a prospective nationwide cohort study.

Setting

The aPL profile of participants was recorded from the laboratory database. Information was collected about thrombotic and pregnancy complications, subsequent medical history, other risk factors for thrombosis, use of prophylactic antithrombotic medication and general health.

Participants

Participants included adult asymptomatic aPL carriers recognized in Finland during 1971–2009.

Main outcome measure

The main outcome measure was incidence of first thrombotic event.

Results

A total of 119 (89% female) aPL carriers were followed for mean (SD) of 9.1 (7.5) years (range 3–41 years). Sixty-one per cent of the study participants had autoimmune disease, most often systemic lupus erythematosus (SLE). Thirty-six of 119 (30%) were either double or triple positive, 56% single lupus anticoagulant (LA) positive, and 8% and 5% single anticardiolipin antibodies (aCL) and anti-β2glycoprotein I antibodies (aβ2GPI) positive, respectively. Nine (7.6%) study patients experienced a first thrombotic event (five DVT, one PE, two MI, one TIA) mean (SD) 7.2 (8.3) years (range 1–26 years) after aPL detection (annual incidence rate 0.8%). All individuals who developed thrombotic complications had autoimmune disease. Annual rate of first thrombotic event in carriers of single positivity (0.65%) was equal to the known risk of thrombosis in the healthy Caucasian population, whereas the rate was two times higher in carriers of double or triple positivity (1.27%). Sixteen of 79 (20%) women experienced pregnancy complications.

Conclusions

Double or triple positivity for aPL is a risk factor for future thrombotic events, especially in individuals with an underlying autoimmune disease, whereas single positivity does not seem to carry an elevated risk of thrombosis.

High positive antibody titers and adverse pregnancy outcome in women with antiphospholipid syndrome

OBJECTIVE

To investigate whether in patients with antiphospholipid syndrome (APS), high positive antibody titers are associated with adverse pregnancy outcome.

DESIGN

A retrospective cohort study of prospectively collected data.

SETTING

Sheba Medical Center, Israel, a tertiary referral center. POPULATION SAMPLE: Pregnant women with APS.

METHODS

Anticardiolipin, a-β2-glycoprotein I antibodies, and lupus anticoagulant were measured before pregnancy. Women were divided into those with antibody titers >four times the upper limit of normal (high positive titer, HPT group), and the rest, into the positive titer (PT) group. All women were treated with daily enoxaparin and aspirin.

MAIN OUTCOME MEASURES

Composite adverse fetal/neonatal outcome, defined as one or more of the following: fetal/neonatal loss, preterm birth ≤ 32 weeks, and birthweight below than 10th percentile. Composite adverse fetal/neonatal outcome was compared between the HPT and PT groups. Maternal adverse outcomes were also compared.

RESULTS

51 women with APS were followed during 55 pregnancies, 20 in the HPT and 35 in the PT groups. The two groups were similar with regard to previous obstetric and clinical characteristics. Among HPT women, only 7/20 (35%) pregnancies culminated in appropriately grown, live-born infants >32 weeks' gestation, compared with 27/35 (77%) PT pregnancies. The risk of adverse fetal/neonatal outcome was 5.7 times higher (95%CI 1.9-17.7) for HPT than for PT women.

CONCLUSIONS

Pregnant women with APS and high positive antiphospholipid antibody titers are a unique and extremely high risk group for adverse fetal/neonatal outcome. Stricter surveillance and possibly additional therapy options should be explored for this patient population.

Antiphospholipid syndrome: laboratory detection, mechanisms of action and treatment

The antiphospholipid syndrome (APS) identifies a condition at increased risk of vascular occlusion and/or pregnancy complications. Patients are defined as having APS if they have at least one clinical (vascular occlusion and/or pregnancy complications) and one laboratory criterion at the same time. The laboratory criteria that define APS are repeated positivity (confirmed 12 weeks apart) for lupus anticoagulants and/or antibodies targeted against cardiolipin or β(2) -glycoprotein I immobilized on solid surfaces. Over the years, APS has attracted the interest of many medical specialties. The aim of this review is to provide an update on (i) the laboratory criteria that determine the presence of APS, (ii) how the antibodies increase the risk of vascular occlusion and foetal loss and (iii) the treatment of the related clinical events.

Incidence of a first thromboembolic event in asymptomatic carriers of high-risk antiphospholipid antibody profile: a multicenter prospective study

Persistent antiphospholipid (aPL) antibodies are occasionally found in subjects without prior history of thromboembolic events (TEs), raising the dilemma of whether to initiate or not a primary thromboprophylaxis. A first TE is considered rare in aPL carriers, but previous studies did not consider the aPL profile nor was the test positivity confirmed in a reference laboratory. In this study, 104 subjects with high-risk aPL profile (positive lupus anticoagulant, anticardiolipin, and anti-β(2)-glycoprotein I antibodies, triple positivity) confirmed in a reference laboratory, were followed up for a mean of 4.5 years. There were 25 first TEs (5.3% per year): the cumulative incidence after 10 years was 37.1% (95% confidence interval [CI], 19.9%-54.3%). On multivariate analysis, male sex (hazard ratio = 4.4; 95% CI, 1.5-13.1, P = .007) and risk factors for venous thromboembolism (hazard ratio = 3.3; 95% CI, 1.3-8.5, P = .01) were independent predictors for TEs. Aspirin did not significantly affect the incidence of TE. In conclusion, the occurrence of a first TE in carriers of high-risk aPL profile is considerable; it is more frequent among male subjects and in the presence of additional risk factors for venous TE. These data can help in the decision to initiate primary thromboprophylaxis in these subjects.

Clinical course of high-risk patients diagnosed with antiphospholipid syndrome

BACKGROUND

The characteristics and the clinical course of antiphospholipid syndrome (APS) in high-risk patients that are positive for all three recommended tests that detect the presence of antiphospholipid (aPL) antibodies have not been described.

METHODS

This retrospective analysis of prospectively collected data examined patients referred to Italian Thrombosis Centers that were diagnosed with definite APS and tested positive for aPL [lupus anticoagulant (LA), anti-cardiolipin (aCL), and anti-beta2-glycoprotein I (beta2GPI) antibodies]. Laboratory data were confirmed in a central reference laboratory.

RESULTS

One hundred and sixty patients were enrolled in this cohort study. The qualifying events at diagnosis were venous thromboembolism (76 cases; 47.5%), arterial thromboembolism (69 cases; 43.1%) and pregnancy morbidity (11 cases; 9.7%). The remaining four patients (2.5%) suffered from catastrophic APS. The cumulative incidence of thromboembolic events in the follow-up period was 12.2% (95% CI, 9.6-14.8) after 1 year, 26.1% (95% CI, 22.3-29.9) after 5 years and 44.2% (95% CI, 38.6-49.8) after 10 years. This was significantly higher in those patients not taking oral anticoagulants as compared with those on treatment (HR=2.4 95% CI 1.3-4.1; P<0.003). Major bleeding associated with oral anticoagulant therapy was low (0.8% patient/years). Ten patients died (seven were cardiovascular deaths).

CONCLUSIONS

Patients with APS and triple positivity for aPL are at high risk of developing future thromboembolic events. Recurrence remains frequent despite the use of oral anticoagulants, which significantly reduces the risk of thromboembolism.

Anti-beta2 glycoprotein-I antibody increases the risk of pregnancy-induced hypertension: a case-controlled study

The aim of this study was to evaluate whether anti-beta2 glycoprotein-I antibody (anti-beta2GPI) of the IgG or IgM classes is associated with the development of pregnancy-induced hypertension (PIH) or preeclampsia in the Japanese population. In a case-controlled cohort study, peripheral blood was obtained at 8-14 weeks of gestation from a consecutive series of 1155 women. The case group comprised 36 patients who later developed PIH during the pregnancy. Of the 36 PIH patients, 13 had severe PIH, 18 had preeclampsia and 11 had severe preeclampsia. One hundred and eleven age- and parity-matched women whose pregnancies ended in normal delivery without obstetric complications were selected as controls. We found that a titer of anti-beta2GPI IgG>or=1.0 U/ml was a risk factor for severe PIH (P=0.023, OR 5.7 95%CI 1.4-22.8). In addition, titers of anti-beta2GPI IgM>or=1.2 U/ml was found to be a risk factor for PIH (P=0.001, OR 8.8 95%CI 1.6-47.5). In women positive for anti-beta2GPI but negative for lupus anticoagulant, anti-cardiolipin, phosphatidylserine-dependent anti-prothrombin, or kininogen-dependent anti-phosphatidylethanolamine antibodies, the presence of anti-beta2GPI was not a significant risk factor for development of PIH or preeclampsia. In conclusion, the presence of anti-beta2GPI antibody represents a risk factor for developing PIH and severe PIH. This finding supports the utility of anti-beta2GPI determination as one of the laboratory criteria for anti-phospholipid syndrome classification. The usefulness of anti-beta2GPI measurement among women without other anti-phospholipid antibodies requires further study.

The geoepidemiology of the antiphospholipid antibody syndrome

Antiphospholipid antibodies (aPL) can be detected by functional (lupus anticoagulant) and/or by solid phase assays (anti-cardiolipin and anti-beta2 glycoprotein I). Although detectable in 1-5% of asymptomatic apparently healthy subjects, persistent aPL are significantly associated with recurrent arterial/venous thrombosis and with pregnancy morbidity. Such an association is the formal classification tool for the antiphospholipid syndrome (APS). The prevalence of the syndrome with no associated systemic connective tissue diseases (primary APS) in the general population is still a matter of debate since there are no sound epidemiological studies in the literature so far. aPL display higher prevalence in systemic lupus erythematosus and rheumatoid arthritis than in other systemic autoimmune diseases. However not all the aPL positive lupus patients display the clinical manifestations. Comparable findings may be found in the paediatric population, although anti-beta2 glycoprotein I antibodies are detected in healthy children more frequently than in adults. High prevalence of aPL has been also reported in clinical manifestations that are not formal APS classification criteria: heart valve disease, livedo reticular, nephropathy, neurological manifestations, and thrombocytopenia. Antiphospholipid antibodies can be associated with infectious processes, active vaccination, drug administration and malignancies. Their prevalence and titres are lower and the relationship with the APS clinical manifestations are less strong than in the previously mentioned conditions. Ethnicity was also reported to influence the prevalence of aPL.

How we diagnose the antiphospholipid syndrome

The antiphospholipid syndrome (APS) is an acquired thrombophilia, characterized by the occurrence of venous and arterial events. This article examines the laboratory and key clinical aspects of APS. Particular focus is given to anti–beta 2-glycoprotein I (β2GPI) antibodies in view of their recent inclusion in the APS classification criteria. The clinical utility of using the β2GPI enzyme-linked immunosorbent assay, in conjunction with the established lupus anticoagulant assays and cardiolipin enzyme-linked immunosorbent assay, for diagnosing and risk stratifying patients suspected of having APS is discussed. The relative importance of the various assays in diagnosing obstetric APS (early and late gestation miscarriages) is explored. The implications of recent epidemiologic findings for possibly understanding the underlying pathophysiologic mechanisms of obstetric APS are highlighted. Insights into which patients with obstetric APS may be at most risk of thrombotic complications are presented.

Current insight into diagnostics and pathophysiology of the antiphospolipid syndrome

The diagnosis of the antiphospholipid syndrome, a non-inflammatory autoimmune disease characterized by thrombosis or pregnancy morbidity in the presence of antiphospholipid antibodies, depends greatly upon laboratory diagnostics. The diagnostic value of all available assays to detect antiphospholipid antibodies and the anticardiolipin assay in particular, is a matter of ongoing debate. Although the presence of lupus anticoagulant correlates best with thrombosis, accurate determination is not always possible due to anticoagulant treatment. Data on the predictive value of alternatives such as the anti-beta2-glycoprotein I and the anti-prothrombin antibody assay are insufficient and prospective cohort studies are needed. Determining antiphospholipid antibody profiles seems to increase diagnostic specificity. Substantial progress has been made in unravelling the pathophysiological mechanisms underlying the antiphospholipid syndrome. Several cellular receptors for antibody-beta2-glycoprotein I complexes have been identified and their roles in cellular activation are being investigated. In vivo data should provide more insight into the importance of the interaction with individual receptors.