Antiprothombin antibodies and the diagnosis of antiphospholipid syndrome

The preliminary classification criteria for definite antiphospholipid syndrome (APS) include the presence of anticardiolipin antibodies (aCL) and/or lupus anticoagulant (LA) as laboratory criteria. However, antiphospholipid antibodies (aPL) are a heterogeneous group of antibodies comprising also antibodies against phospholipid-binding proteins or their complexes with phospholipids. Prothrombin is one of the antigen recognized by aPL. In the last decade, there has been increasing interest in antibodies against prothrombin alone and those against phosphatidylserine-prothrombin complex. The latter, phosphatidylserine-dependent antiprothrombin antibodies (aPT), have been closely associated with APS and LA. In this paper, we review the properties of antiprothrombin antibodies.     

Antiphospholipid syndrome diagnosis: an update

The antiphospholipid syndrome (APS) is characterized by arterial and/or venous thrombosis and pregnancy morbidity in association with the persistent presence of autoantibodies called antiphospholipid antibodies (APAs). APAs are a heterogeneous group of circulating autoantibodies that can be detected either by phospholipid-dependent coagulation test for lupus anticoagulant (LA) or ELISA test for anticardiolipin and anti-β2GPI antibodies. In 2006, the revised criteria for the diagnosis of APS introduce the anti-β2GPI antibodies as a new biological criterion and highlight the necessity to increase the interval between two positive APA test from 6 to 12 weeks. However, despite these updated criteria, the diagnosis of APS remains challenging and we proposed here to make an overview of the latest evolution in the diagnosis of this syndrome.     

Antiphospholipid antibodies, antiphospholipid syndrome and infections

Since the association between antiphospholipid antibodies (aPL) and syphilis was first described, many other viral, bacterial and parasitic infections have been shown to induce antiphospholipid antibodies, notably anticardiolipin antibodies (aCL). A review of the literature shows that while aCL occur frequently in viral infections, particularly in HIV (49.75%), HBV (24%) and HCV (20%), it is very rarely associated with anti-beta2 glycoprotein I antibodies (anti-beta2GPI) and is not correlated with thrombosis risk or hematological manifestations of the antiphospholipid syndrome (APS). Concerning bacterial infections, aCL is often present in leprosy (42.7%), where it is frequently associated with the presence of anti-beta2GPI (44.8%), and in syphilis infections (8 to 67%), though without correlation with thrombotic events. Though few individual patients with unequivocal infection-induced aPL satisfy criteria for APS, the lack of statistical association with thrombotic events strongly argues against the identification of a true APS subset in this context. However, physicians should keep in mind the fact that an infection, generally bacterial, in patients with confirmed APS, may lead to catastrophic antiphospholipid syndrome with a possible fatal outcome.     

Antiphospholipid antibody profiling — Time for a new technical approach?

Detection of anti-phospholipid (aPL) antibodies for state-of-the art diagnosis of antiphospholipid syndrome(APS) still remains a laboratory challenge due to the great diversity of aPL antibodies and their relevance with regard to the diagnostic criteria. According to the recently revised classification criteria for APS, several enzyme-linked immunosorbent assays (ELISAs) should be performed simultaneously in routine laboratories for the detection of aPL antibodies. Therefore, new approaches to aPL profiling have been proposed recently to provide information regarding diagnosis and eventually outcome in APS patients. Multiplex analysis could meet the increasing demand for cost-efficient detection and profiling of aPL antibodies. Multi-line immunodot assays or bead-based multiplex techniques candidate as alternatives to assess several aPL antibodies simultaneously employing different solid-phases for bound/free separation of reactants. Particularly, multi-line immunodot assays present an alternative to ELISA for aPL antibody detection and profiling in APS patients. The use of hydrophobic membranes as solid-surface by this technique appears to offer a distinct solid-phase reaction environment for the assessment of aPL antibodies. This article reviews novel developments in the field of laboratory diagnostics of APS with special emphasis on multiplex assays.     

“Non-criteria” antiphospholipid syndrome: A nomenclature proposal

The classification criteria for antiphospholipid syndrome (APS) generate discussion, with a growing impression that certain patients not fulfilling these criteria might be inadequately excluded from the classification. Nonetheless, these “non-criteria” patients are heterogeneously defined across different publications. We reviewed the “non-criteria” APS subgroups depicted in the literature and attempted to organize these subsets in a nomenclature proposal that could be used for research purposes.We established four potential patient profiles, grouped under the broad term “non-criteria APS”: (A) “Seronegative APS”: patients fulfilling clinical criteria, plus “non-criteria” manifestations, with persistently negative antiphospholipid antibodies (aPL); (B) “Clinical non-criteria APS”: patients with “non-criteria” manifestations, plus aPL positivity fulfilling the classification criteria; (C) “Incomplete laboratory APS”: patients fulfilling clinical criteria, plus positive aPL, but not fulfilling the classification criteria (low titer aPL); and (D) “Laboratory non-criteria APS”: patients fulfilling clinical criteria, with negative or low titer criteria aPL, plus positive “non-criteria” aPL. This categorization could allow for a more homogeneous research approach to APS, enabling more sustained and universal conclusions.     

Beta-2-glycoprotein-I, infections, antiphospholipid syndrome and therapeutic considerations

Evidence supports the association between infectious agents, antiphospholipid syndrome (APS), and the presence of antiphospholipid antibodies and anti-beta2-glycoprotein-I (beta2GPI) antibodies. Several mechanisms have been proposed to explain the role of bacteria/viruses in induction of an autoimmune condition, such as molecular mimicry between structures of a pathogen and self antigen and bystander activation or bacterial/viral superantigens. Protein databases reveal high homologies between the beta2GPI-related synthetic peptides and infectious agents. Studies employing experimental APS models proved molecular mimicry between beta2GPI-related synthetic peptides, which serve as target epitopes for anti-beta2GPI Abs, and structures within bacteria, viruses (e.g., CMV), and tetanus toxoid. Any explanation of how microbial infections might induce APS must take into account the genetic predisposition. In this paper, we discuss the association of antiphospholipid antibodies, infectious states, and molecular mimicry as a proposed mechanism for development of APS.     

Antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a disease characterized by venous and arterial thromboses or spontaneous abortions and the repeated detection of antiphospholipid antibodies (aPL). APS may be associated with another autoimmune disease (secondary APS), particularly systemic lupus erythematosus (SLE), or unrelated to an underlying disease (primary APS). APS affects almost all organs. In addition to the clinical criteria, lupus anticoagulant testing and immunological aPL determinations are required to establish the diagnosis of APS.     

Livedo Reticularis as a Criterion for Antiphospholipid Syndrome

Many consensus meetings were organized in an attempt to improve the present criteria for antiphospholipid syndrome (APS) classification. In this regard, a high prevalence of antiphospholipid antibodies in systemic lupus erythematosus patients was reported in association with the presence of livedo reticularis (LR). In these studies, the association between LR, migraine, and the development of thrombosis (strokes, valvular dysfunctions) was evident. During the last decade, it was strongly suggested that many clinical symptoms (LR, valvular dysfunctions) or laboratory features (thrombocytopenia) should be considered as "minor criteria" for APS. The inclusion of these clinical symptoms in the criteria for APS classification could become of additive value especially when they exist together in one patient. This review summarizes the data that question or support this idea.     

Antiphospholipid Syndrome Infectious Origin

Antiphospholipid syndrome (APS) is characterized by the presence of pathogenic autoantibodies against beta 2-glycoprotein-I (beta 2GPI). The factors causing production of anti-beta 2GPI remain unidentified, but an association with infectious agents has been reported. Studies on experimental APS models proved that molecular mimicry between beta 2GPI-related synthetic peptides and structures within bacteria, viruses, tetanus toxoid, and CMV are a cause for experimental APS. Any explanation of how microbial infections might set off APS must take into account the observation that all individuals appear to harbor potentially autoreactive lymphocytes, as well as natural antiphospholipid antibodies, but that these cells or antibodies remain innocuous unless somehow activated. Herein, we discuss the association of antiphospholipid antibodies in the infectious state, molecular mimicry as a proposed cause for development of APS, and the contribution of the database to this topic.     

Evaluation of novel assays for the detection of autoantibodies in antiphospholipid syndrome

Patients with antiphospholipid syndrome (APS) present with clinical features of recurrent thrombosis and pregnancy morbidity and persistently test positive for the presence of antiphospholipid antibodies (aPL). At least one clinical (vascular thrombosis or pregnancy morbidity) and one lab-based (positive test result for lupus anticoagulant, anticardiolipin antibodies and/or anti-β2-glycoprotein 1 antibodies) criterion have to be met for a patient to be classified as having APS. Nevertheless, the clinical variety of APS encompasses additional signs and symptoms, potentially affecting any organ, that cannot be explained exclusively by a prothrombotic state. Those manifestations, also known as extra-criteria manifestations, include haematologic (thrombocytopenia and haemolytic anaemia), neurologic (chorea, myelitis and migraine) manifestations as well as the presence of livedo reticularis, nephropathy and valvular heart disease. The growing body of evidence describing the clinical aspect of the syndrome has been paralleled over the years by emerging research interest focusing on the development of novel biomarkers that might improve the diagnostic accuracy for APS when compared to the current aPL tests. This review will focus on the clinical utility of extra-criteria aPL specificities. Besides, the promising role of a new technology using particle based multi-analyte testing that supports aPL panel algorithm testing will be discussed. Diagnostic approaches to difficult cases, including real-world case studies investigating the diagnostic added value of extra criteria aPL, particularly anti-phosphatidylserine/prothrombin, will also be examined.     

Diagnosis and classification of the antiphospholipid syndrome

The antiphospholipid syndrome (APS) is defined by the occurrence of venous and arterial thromboses, often multiple, and recurrent fetal losses, frequently accompanied by a moderate thrombocytopenia, in the presence of antiphospholipid antibodies (aPL). Some estimates indicate that the incidence of the APS is around 5 new cases per 100,000 persons per year and the prevalence around 40–50 cases per 100,000 persons. The aPL are positive in approximately 13% of patients with stroke, 11% with myocardial infarction, 9.5% of patients with deep vein thrombosis and 6% of patients with pregnancy morbidity. The original classification criteria for the APS were formulated at a workshop in Sapporo, Japan, in 1998, during the 8th International Congress on aPL. The Sapporo criteria, as they are often called, were revised at another workshop in Sydney, Australia, in 2004, during the 11th International Congress on aPL. At least one clinical (vascular thrombosis or pregnancy morbidity) and one laboratory (anticardiolipin antibodies, lupus anticoagulant or anti-β₂-glycoprotein I antibodies) criterion had to be met for the classification of APS.     

Clinical and epidemiological aspects in the antiphospholipid syndrome

The antiphospholipid syndrome (APS) is defined by the occurrence of venous and arterial thromboses, often multiple, and pregnancy morbidity (mainly, recurrent fetal losses and premature births), frequently accompanied by a moderate thrombocytopenia, in the presence of antiphospholipid antibodies (aPL), namely lupus anticoagulant (LA), anticardiolipin antibodies (aCL), or both. Other autoantibodies have also been detected in many patients with an APS, such as anti-beta2 glycoprotein I (GPI), antimitochondrial (M5 type), antiendothelial cell, antiplatelet, antierythrocyte, and antinuclear antibodies. The APS can be found in patients having neither clinical nor laboratory evidence of another definable condition (primary APS) or it may be associated with other diseases. Systemic lupus erythematosus (SLE) is the disorder in which an APS is most commonly associated. Less frequently, aPL and, rarely, an APS may also be encountered in other groups of patients (Table 1) (1).     

Clinical relevance of antiprothrombin antibodies

Antiprotrombin antibodies belong to the family of antiphospholipid antibodies (aPLs). The clinical relevance of antiprothrombin antibodies has not been established and it depends on the applied detection method. Antibodies against phosphatidylserine-prothrombin complex (aPS/PT) are closely associated with clinical features of antiphospholipid syndrome (APS) and lupus anticoagulant rather than antibodies against prothrombin alone. The determination of aPS/PT in routine clinical practice should be done in conjunction with other aPLs detection to improve the likelihood of recognising the APS, which would ultimately facilitate the management of the disease.     

Update on the current recommendations and outcomes in pregnant women with antiphospholipid syndrome

Pregnancy morbidity is part of the clinical spectrum of the antiphospholipid syndrome (APS), a chronic autoimmune condition serologically characterized by the persistent positivity of antiphospholipid antibodies (aPL). Antiplatelet and anticoagulant agents are the mainstay of the treatment of obstetric APS. However, there is an ongoing debate about the optimal management of women with most severe aPL-mediated obstetric complications, women not fulfilling APS criteria and those with refractory disease. Unfortunately, the literature cannot provide definite answers to these controversial issues, being flawed by many limitations. The evidence supporting the recommended therapeutic management of different aPL-related obstetrical clinical manifestations is presented, with a critical appraisal of each approach.     

Atherosclerosis in primary antiphospholipid syndrome

Antiphospholipid syndrome (APS) is the most common cause of acquired thrombophilia, but experimental and clinical evidence accumulated over the years suggest that the clinical manifestations of APS go beyond those of a simple hypercoagulable state. Although still a controversial topic, the elevated risk of atherosclerosis in systemic lupus erythematosus seems little accounted for by the presence of antiphospholipid antibodies, whereas premature atherosclerosis has been addressed in few series of patients with primary APS. The available data in primary APS suggest that traditional risk factors for atherosclerosis are less involved in arterial disease, rather antiphospholipid antibodies appear as major players. Their effect on the coagulation system, the vessel wall and on the antioxidant/oxidant balance impairs vascular homeostasis, leading to premature arterial thickening.     

The Role of Complement in the Antiphospholipid Syndrome-Associated Pathology

The antiphospholipid syndrome (APS) is characterized by arterial and/or venous thromboses, pregnancy loss, and the presence of anticardiolipin antibodies. The pathogenic mechanisms that lead to these clinical manifestations are incompletely understood. Although a direct pathogenic role of antiphospholipid antibodies has been established, including their role in endothelial cell and platelet activation, there is growing evidence that activation of the complement pathway may contribute to the pathogenesis of APS. Vital information has been obtained from studies exploring the features of pregnancy morbidity and thrombosis using complement deficient murine models. These studies are providing the foundation for the development of new therapeutic options to optimize the management of APS.     

Pulmonary Hypertension,Antiphospholipid Antibodies,and Syndromes

Antiphospholipid antibodies have been associated with two types of pulmonary hypertension (PHT), the thromboembolic type, after deep venous thromboses in the lower limbs complicated by pulmonary embolism and the “primary” plexogenic type. The PHT may occur in the absence of any other manifestations of the antiphospholipid syndrome (APS), and cases have been recorded with very high levels of antiphospholipid antibodies. It may also accompany systemic lupus erythematosus (SLE) and may manifest with or without other features of the APS. It may also form part of the clinical presentation of a “primary” APS. Its prevalence is of the order of 1.8–3.5% of the manifestations of the APS depending on the series. Primary “idiopathic” PHT has long been regarded as an “immunological” disorder. Its manifestations are essentially to the primary type seen with the connective tissue disorders such as SLE, APS, mixed connective tissue disease, calcinosis, Raynaud phenomenon, esophageal dysmotility, sclerodactyly, and telangiectasia variety of systemic sclerosis and Sjögren’s syndrome. The high prevalence of PHT in patients with human immunodeficiency virus infection who demonstrate low CD4 counts points to a close relationship between the T regulatory cells (Treg) and the development of PHT, and this hypothesis is discussed in this review. Genetic and chromosomal aspects of PHT are also discussed.     

Diagnosis and management for antiphospholipid syndrome

It has been reported that antiphospholipid antibodies have the diversity against epitopes and the clinical significance, while the concept of antiphospholipid syndrome has been established. Dr. Harris and Dr. Hughes proposed the diagnostic criteria for antiphospholipid syndrome, and their criteria were widely used. Thrombosis, recurrent fetal loss (intrauterine fetal death), thrombocytopenia, IgG anticardiolipin antibodies and lupus anticoagulants were adopted in their criteria. However, recent studies have revealed the evaluation of the standardization of the methods to detect antiphospholipid antibodies and the clinical significance of both anti-cardiolipin-beta 2-GPI complex antibodies and other isotypes of antiphospholipid antibodies. Thus, the preliminary classification criteria for antiphospholipid syndrome have been discussed. It has been reported that anticoagulation therapy is effective in the management of antiphospholipid syndrome by the recent retrospective studies. It is necessary to confirm these points by the prospective study in the near future.     

The emerging role of multiple antiphospholipid antibodies positivity in patients with antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by clinical symptoms of vascular thrombosis and/or pregnancy morbidity in the presence of autoimmune antiphospholipid antibodies (aPL). Current laboratory APS criteria include the presence of at least one of the three relevant aPL: lupus anticoagulant, anticardiolipin antibodies and anti-β₂ glycoprotein I antibodies. Therefore, patients could have a single aPL pattern or combinations of aPL. Evidence arising from clinical experience indicates that patients having the highest aPL titer and simultaneous aPL detected by different tests have a worse prognosis and a higher probability of recurrence of the APS clinical features. In recent years, an emerging role of multiple aPL positivity in the identification of high-risk patients with aPL/APS is evident. This paper will review the current knowledge on the clinical relevance of having single or multiple aPL positivity.