P. G. De Groot

Catastrophic antiphospholipid syndrome: international consensus statement on classification criteria and treatment guidelines

The term ‘catastrophic’ antiphospholipid syndrome (APS) is used to define an accelerated form of APS resulting in multiorgan failure. Although catastrophicAPS patients represent less than 1% of all patients with APS, they are usually in a life-threatening medical situation that requires high clinical awareness. The careful and open discussion of several proposals by all participants in the pre-symposium workshop on APS consensus, held in Taormina on occasion of the 10th International Congress on aPL and chaired by Munther A Khamashta and Yehuda Shoenfeld (29 September 2002), has allowed the acceptation of a preliminary set of classification criteria. On the other hand, the optimal management of catastrophicAPS must have three clear aims: to treat any precipitating factors (prompt use of antibioticsif infection is suspected, amputation for any necrotic organ, high awareness in patients with APS who undergo an operation or an invasive procedure), to prevent and to treat the ongoing thrombotic events and to suppress the excessive cytokine ‘storm’. Anticoagulation (usually intravenous heparin followed by oral anticoagulants), corticosteroids, plasma exchange, intravenous gammaglobulins and, if associated with lupus flare, cyclophosphamide, are the most commonly used treatments for catastrophic APS patients.

Morbidity and mortality in the antiphospholipid syndrome during a 10-year period: a multicentre prospective study of 1000 patients

Objectives To assess the prevalence of the main causes of morbi-mortality in the antiphospholipid syndrome (APS) during a 10-year-follow-up period and to compare the frequency of early manifestations with those that appeared later. Methods In 1999, we started an observational study of 1000 APS patients from 13 European countries. All had medical histories documented when entered into the study and were followed prospectively during the ensuing 10 years. Results 53.1% of the patients had primary APS, 36.2% had APS associated with systemic lupus erythematosus and 10.7% APS associated with other diseases. Thrombotic events appeared in 166 (16.6%) patients during the first 5-year period and in 115 (14.4%) during the second 5-year period. The most common events were strokes, transient ischaemic attacks, deep vein thromboses and pulmonary embolism. 127 (15.5%) women became pregnant (188 pregnancies) and 72.9% of pregnancies succeeded in having one or more live births. The most common obstetric complication was early pregnancy loss (16.5% of the pregnancies). Intrauterine growth restriction (26.3% of the total live births) and prematurity (48.2%) were the most frequent fetal morbidities. 93 (9.3%) patients died and the most frequent causes of death were severe thrombosis (36.5%) and infections (26.9%). Nine (0.9%) cases of catastrophic APS occurred and 5 (55.6%) of them died. The survival probability at 10 years was 90.7%. Conclusions Patients with APS still develop significant morbidity and mortality despite current treatment. It is imperative to increase the efforts in determining optimal prognostic markers and therapeutic measures to prevent these complications.

Patients with antiphospholipid antibodies and venous thrombosis should receive long term anticoagulant treatment.

OBJECTIVE--To determine whether the finding of antiphospholipid antibodies in patients with venous thromboembolic episodes should influence the duration of treatment with anticoagulant drugs by mouth. METHODS--A retrospective study was carried out in 19 patients with antiphospholipid antibodies and a history of venous thromboembolic episodes. The median follow up from the first venous thromboembolic episode was 93 months and the median age at this episode was 26 years. The patients had in total 34 venous thromboembolic episodes. The total follow up period comprised 32 periods with and 23 periods without anticoagulant drugs. RESULTS--The probability of being free of recurrent venous thromboembolic episodes, calculated by the Kaplan-Meier method, was significantly influenced by the use of anticoagulant drugs. Patients receiving oral anticoagulants had at eight years a 100% probability of survival without recurrence, whereas patients in whom anticoagulant drugs were stopped had a 50% probability of a recurrent venous thromboembolic episode at two years, and a 78% probability of recurrence at eight years. CONCLUSION--Patients with venous thromboembolic episodes and antiphospholipid antibodies have a high risk for recurrent venous thromboembolic episodes and long term treatment with anticoagulant drugs by mouth is an effective prophylaxis.

The association between circulating antibodies against domain I of beta2-glycoprotein I and thrombosis: an international multicenter study

Summary.  Background: Diagnosis of the antiphospholipid syndrome (APS) is difficult as a result of limited specificity of existing assays for detecting clinically relevant antiphospholipid antibodies. Anti‐beta2‐glycoprotein I (beta2GPI) antibodies play a central role in the disease process of APS. Objectives: We have investigated the relation between antiphospholipid antibodies with specificity for domain I of beta2GPI and thrombosis/pregnancy morbidity in an international multicenter study. Patients/methods: Four hundred and seventy‐seven patients derived from nine different centres met the inclusion criterion of having anti‐beta2GPI antibodies in their plasma/serum. Clinical data and results of tests for lupus anticoagulant, anti‐cardiolipin antibodies and anti‐beta2GPI antibodies were established at the different centres of inclusion. After being re‐tested for the presence of IgG and/or IgM anti‐beta2GPI antibodies, the samples were tested for the presence of IgG‐directed against domain I of beta2GPI and results were correlated with the thrombotic and obstetric history. Results: Re‐testing for the presence of anti‐beta2GPI antibodies resulted in inclusion of 442/477 patients. IgG class anti‐domain I antibodies were present in plasma of 243/442 patients (55%). 201/243 (83%) had a history of thrombosis. This resulted in an odds ratio of 3.5 (2.3–5.4, 95% confidence interval) for thrombosis. Anti‐domain I IgG antibodies were also significantly correlated with obstetric complications [odds ratio: 2.4 (1.4–4.3, 95% confidence interval)]. Conclusion: In this multicenter study, the detection of IgG antibodies that are directed against domain I of beta2GPI proved to be more strongly associated with thrombosis and obstetric complications than those detected using the standard anti‐beta2GPI antibody assay.

Increased platelet deposition on atherosclerotic coronary arteries.

A ruptured atherosclerotic plaque leads to exposure of deeper layers of the plaque to flowing blood and subsequently to thrombus formation. In contrast to the wealth of data on the occurrence of thrombi, little is known about the reasons why an atherosclerotic plaque is thrombogenic. One of the reasons is the relative inaccessibility of the atherosclerotic plaque. We have circumvented this problem by using 6-microns cryostat cross sections of human coronary arteries. These sections were mounted on coverslips that were exposed to flowing blood in a rectangular perfusion chamber. In normal-appearing arteries, platelet deposition was seen on the luminal side of the intima and on the adventitia. In atherosclerotic arteries, strongly increased platelet deposition was seen on the connective tissue of specific parts of the atherosclerotic plaque. The central lipid core of an advanced plaque was not reactive towards platelets. The results indicate that the atherosclerotic plaque by itself is more thrombogenic than the normal vessel wall. To study the cause of the increased thrombus formation on the atherosclerotic plaque, perfusion studies were combined with immunohistochemical studies. Immunohistochemical studies of adhesive proteins showed enrichment of collagen types I, III, V, and VI, vitronectin, fibronectin, fibrinogen/fibrin, and thrombospondin in the atherosclerotic plaque. Laminin and collagen type IV were not enriched. von Willebrand Factor (vWF) was not present in the plaque. The pattern of increased platelet deposition in serial cross sections corresponded best with areas in which collagen types I and III were enriched, but there were also areas in the plaque where both collagens were enriched but no increased reactivity was seen. Inhibition of platelet adhesion with a large range of antibodies or specific inhibitors showed that vWF from plasma and collagen types I and/or III in the plaque were involved. Fibronectin from plasma and fibronectin, fibrinogen, laminin, and thrombospondin in the vessel wall had no effect on platelet adhesion. We conclude that the increased thrombogenicity of atherosclerotic lesions is due to changes in quantity and nature of collagen types I and/or III.

Lupus anticoagulants and the risk of a first episode of deep venous thrombosis

Summary.  We have determined lupus anticoagulants, anti‐β2 glycoprotein I (β2GPI) and antiprothrombin antibodies in the Leiden Thrombophilia Study, a population‐based case–control study designed to determine risk factors for deep venous thrombosis (DVT). Lupus anticoagulant (LAC) was measured in 473 patients and 472 control subjects. Four control subjects (0.9%) and 14 patients (3.1%) had a positive LAC, resulting in a 3.6‐fold increased risk [odds ratio (OR) 3.6, 95% CI: 1.2–10.9]. Of the total population, 49 were positive for anti‐β2GPI antibodies: 15 controls (3.4%) and 34 patients (7.5%), implying a 2.4‐fold increased risk (95% CI: 1.3–4.2). Antiprothrombin antibodies were present in 114 subjects: 48 controls (11.0%) and 66 cases (14.6%) with an OR of 1.4 (95% CI: 1.0–2.1). When LAC was considered in the co‐presence of antiprothrombin or anti‐β2GPI antibodies the OR increased to 10.1 (95% CI: 1.3–79.8). A LAC without a positive anti‐β2GPI or antiprothrombin test was not associated with a risk for DVT (OR 1.3, 95% CI: 0.3–6.0). This study demonstrates that the presence of LAC, anti‐β2GPI antibodies and antiprothrombin antibodies are risk factors for DVT in a general population. The strongest association holds for the combination LAC and the presence of anti‐β2GPI or antiprothrombin antibodies.

Coagulation screen is more specific than the anticardiolipin antibody ELISA in defining a thrombotic subset of lupus patients.

In 111 lupus patients we compared the potential of the IgG and IgM anticardiolipin antibody (ACA) enzyme linked immunosorbent assay (ELISA) and four different lupus anticoagulant (LAC) assays (partial thromboplastin time (PTT) of a 1:1 mixture of patient and control plasma with phospholipids from animal (PTT-st) or human brain (PTT-HB); PTT with dilutions of human brain phospholipids (PL dilution); and kaolin clotting time of mixtures of patient and control plasma (KCT] to identify patients with thrombosis (26/111), fetal loss (19/46), and/or thrombocytopenia (11/106). The highest specificity for thrombosis (87%) was found with PTT-HB and PL dilution (sensitivity 65%, detection rate 61%); for fetal loss (93%) with PL dilution (sensitivity 47%; detection rate 82%), and for thrombocytopenia (83%) with KCT (sensitivity 82%; detection rate 36%). Compared with LAC assays, the sensitivity of ACA-ELISA was high (greater than or equal to 77%), but specificity (less than or equal to 51%) and detection rate (less than or equal to 52%) were low. So, a panel of three LAC assays (PTT-HB, PL dilution, and KCT) can identify lupus patients apparently at risk for thrombosis, fetal loss, and/or thrombocytopenia, whereas the ACA-ELISA is insufficiently specific.

‘Criteria’ aPL tests: Report of a Task Force and preconference workshop at the 13th International Congress on Antiphospholipid Antibodies, Galveston, Texas, April 2010:

Current classification criteria for definite antiphospholipid syndrome (APS) mandate the use of one or more of three positive ‘standardized’ laboratory assays to detect antiphospholipid antibodies (aPL) (viz: anticardiolipin [aCL] IgG and IgM; anti-β2glycoprotein I [anti-β2GPI] antibodies IgG and IgM; and/or a lupus anticoagulant [LAC]), when at least one of the two major clinical manifestations (thrombosis or pregnancy losses) are present. Although, efforts of standardization for these ‘criteria’ aPL tests have been conducted over the last 27 years, reports of inconsistencies, inter-assay and inter-laboratory variation in the results of aCL, LAC, and anti-β2GPI, and problems with the interpretation and the clinical value of the tests still exist, which affect the consistency of the diagnosis of APS. A Task Force of scientists and pioneers in the field from different countries, subdivided in three working groups, discussed and analyzed critical questions related to ‘criteria’ aPL tests in an evidence-based manner, during the 13th International Congress on Antiphospholipid Antibodies (APLA 2010, April 13–16, 2010, Galveston, TX). These included: review of the standardization and the need for international consensus protocol for aCL and anti-β2GPI tests; the use of monoclonal and/or polyclonal standards in the calibration curve of those tests; and the need for establishment of international units of measurement for anti-β2GPI tests. The group also reviewed the recently updated guidelines for LAC testing, and analyzed and discussed the possibility of stratification of ‘criteria’ aPL tests as risk factors for APS, as well as the clinical value of single positive vs. multiple aPL positivity. The group members presented, discussed, analyzed data, updated and re-defined those critical questions at a preconference workshop that was open to congress attendees. This report summarizes the findings, conclusions, and recommendations of this Task Force.

β(2) -Glycoprotein I: evolution, structure and function.

Summary.  β2‐Glycoprotein I (β2‐GPI) is a protein that circulates in blood at high concentrations. The function of β2‐GPI has long been an enigma. More than 20 years ago, it was discovered that β2‐GPI is the major antigen for the circulating antibodies in the antiphospholipid syndrome. However, this knowledge has not advanced our understanding of the physiologic role of the protein. In recent years, new insights have suggested an important function of this protein in innate immunity. β2‐GPI was found to scavenge lipopolysaccharide and was able to clear unwanted anionic cellular remnants such as microparticles from the circulation. The function of β2‐GPI seems to depend on the structural conformation of the protein, and it has been established that β2‐GPI can exist in at least two conformations. In this review, we will highlight and summarize the current knowledge on this protein.

Platelet activation by dimeric β2‐glycoprotein I requires signaling via both glycoprotein Ibα and apolipoprotein E receptor 2′

Summary.  Background: Dimerization of β2‐glycoprotein I (β2‐GPI) by autoantibodies is thought to trigger the clinical manifestations observed in the antiphospholipid syndrome. Arterial thrombosis, a frequently occurring clinical manifestation of the antiphospholipid syndrome, is a process in which platelets play a crucial role. Previous work has shown that binding of dimeric β2‐GPI to the platelet receptors apolipoprotein E receptor 2′ (ApoER2′) and glycoprotein Ibα (GPIbα) mediates increased platelet activation in an in vitro thrombosis model. Objective: The individual roles of ApoER2′ and GPIbα in mediating platelet activation by dimeric β2‐GPI has hitherto been unclear. In this study, we have determined the roles of either receptor in platelet activation by dimeric β2‐GPI. Methods: Platelet activation by dimeric β2‐GPI was studied under conditions of flow. Intracellular signaling induced by dimeric β2‐GPI was subsequently analyzed by means of sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS‐PAGE) and western blot analysis. Results: The increase in platelet deposition onto a fibronectin surface under conditions of flow by dimeric β2‐GPI was completely abolished by inhibition of the interaction of dimeric β2‐GPI with either GPIbα or ApoER2′. Upon platelet stimulation with dimeric β2‐GPI, GPIbα translocated to the cytoskeleton via the scaffold protein 14‐3‐3ζ. Concomitantly, ApoER2′ dissociated from the adapter protein Disabled1, presumably through phosphorylation of the cytoplasmic tail. Inhibition of one process could not inhibit the other. Conclusion: We show that dimeric β2‐GPI signals via two distinct pathways in platelets, both of which are required for platelet activation. Abrogation of either signal results in loss of activation.