Recent advances in the diagnosis of antiphospholipid syndrome

Antiphospholipid antibodies are autoantibodies directed against anionic phospholipids or protein-phospholipid complexes measured in solid-phase immunoassays such as anticardiolipin (aCL) antibody or detected in phospholipid-dependent clotting tests as lupus anticoagulant (LA). The term "antiphospholipid syndrome (APS)" was first coined to denote the clinical association between antiphospholipid antibodies and a syndrome of episodes of thrombosis in arteries and/or veins, pregnancy loss, and thrombocytopenia. The diagnosis of APS is based on the finding of "moderate-to-high" aCL antibody titer and/or an LA test with any one of the characteristic clinical features presented. Recently, the diagnostic criteria of APS was revised and several newer assays that use phosphatidylserine, a mixture of negatively charged phospholipids or beta2-glycoprotein 1 (beta2-GP1) have been proposed for more specific measurements of antibodies present in APS. In this section, recent progress in the laboratory diagnosis of antiphopholipid syndrome will be discussed.     

Recent advances in the diagnosis of antiphospholipid syndrome

Antiphospholipid antibodies are autoantibodies directed against anionic phospholipids or protein-phospholipid complexes measured in solid-phase immunoassays such as anticardiolipin (aCL) antibody or detected in phospholipid-dependent clotting tests as lupus anticoagulant (LA). The term “antiphospholipid syndrome (APS)” was first coined to denote the clinical association between antiphospholipid antibodies and a syndrome of episodes of thrombosis in arteries and/or veins, pregnancy loss, and thrombocytopenia. The diagnosis of APS is based on the finding of “moderate-to-high” aCL antibody titer and/or an LA test with any one of the characteristic clinical features presented. Recently, the diagnostic criteria of APS was revised and several newer assays that use phosphatidylserine, a mixture of negatively charged phospholipids or β2-glycoprotein 1 (β2-GP1) have been proposed for more specific measurements of antibodies present in APS. In this section, recent progress in the laboratory diagnosis of antiphopholipid syndrome will be discussed.     

Laboratory diagnosis and management challenges in the antiphospholipid syndrome

The antiphospholipid syndrome (APS) is characterized by recurrent arterial and/or venous thrombosis and pregnancy morbidity manifested by early or late losses. Laboratory diagnosis ofAPS relies on the demonstration of a positive test for antiphospholipid antibodies (aPL). In clinical practice, the gold standard tests are those that detect anticardiolipin antibodies (aCL) and/or the lupus anticoagulant (LA). Although other specificities for aPL have been described their clinical utility and standardization has still to be established. Persistence of aPL positive tests must be demonstrated, and other causes and underlying factors considered. Although it is universally recognized that the routine screening tests (aCL and/or LA) might miss some cases, careful differential diagnosis and repeat testing are mandatory before the diagnosis of 'seronegative APS' can be made. Correct identification of patients with APS is important, because prophylactic anticoagulant therapy can prevent thrombosis from recurring, and treatment of affected women during pregnancy can improve fetal and maternal outcome.     

Diagnosis of antiphospholipid syndrome

Antiphospholipid syndrome is a multisystem autoimmune disease, characterized by recurrent vascular thrombosis and/or pregnancy losses in the presence of persistently positive antiphospholipid antibodies. In clinical practice, testing for anticardiolipin antibodies and lupus anticoagulant is mandatory for the laboratory diagnosis of antiphospholipid syndrome. Identification of patients with antiphospholipid syndrome is important, as prophylactic anticoagulant therapy may prevent thrombosis from recurring, and treatment during pregnancy can improve fetal and maternal outcome.     

Antiphospholipid-thrombosis syndromes

Antiphospholipid antibodies are strongly associated with thrombosis and appear to be the most common of the acquired blood protein defects causing thrombosis. Based upon our experience, approximately 25% of patients with unexplained venous thrombosis, approximately 60% of patients with cerebrovascular thrombosis, approximately 37% of patients with transient ischemic attacks, approximately 18% with premature coronary artery thrombosis and approximately 60% of patients with recurrent fetal loss (recurrent miscarriage syndrome) harbor antiphospholipid antibodies. Although the precise mechanism(s) whereby antiphospholipid antibodies alter hemostasis to induce a hypercoagulable state remain unclear, several theories have been advanced. Since the aPTT is unreliable in patients with lupus anticoagulant and is not usually prolonged in patients with anticardiolipin antibodies, definitive tests, ELISA for IgG, IgA and IgM anticardiolipin antibodies and the dilute Russel's viper venom time (followed by cephalin correction for confirmation) for lupus anticoagulant should be immediately ordered when suspecting the antiphospholipid syndrome in individuals with otherwise unexplained thrombotic or thromboembolic events or recurrent fetal loss. However, if one strongly suspects antiphospholipid thrombosis syndrome clinically and assays for lupus anticoagulants and anticardiolipin antibodies are negative, specific assays for all three idiotypes of phosphatidylserine, phosphatidylethanolamine, phosphatidylcholine, phosphatidylinositol and phosphatidylglycerol are available and should be considered. These may clearly be indicated for difficult diagnostic cases of fetal wastage syndrome, and cerebrovascular events, but their significance in other types of thrombosis, particularly venous, remains unclear at present. Since about 65% of patients with antiphospholipid antibodies will fail warfarin therapy (rethrombose), it is important to define this common defect and institute appropriate antithrombotic therapy for appropriate time periods.     

Antiphospholipid syndrome and thrombosis.

Antiphospholipid antibodies [such as anticardiolipin antibodies (ACLA)] are strongly associated with thrombosis and appear to be the most common of the acquired blood protein defects causing thrombosis. Although the precise mechanism(s) whereby antiphospholipid antibodies alter hemostasis to induce a hypercoagulable state remain unclear, several theories have been advanced. The most common thrombotic events associated with ACLA are deep vein thrombosis and pulmonary embolus (type I syndrome), coronary or peripheral artery thrombosis (type II syndrome) or cerebrovascular/retinal vessel thrombosis (type III syndrome), and occasionally patients present with mixtures (type IV syndrome). Type V patients are those with antiphospholipid antibodies and fetal wastage syndrome. It is as yet unclear how many seemingly normal individuals who may never develop manifestations of antiphospholipid syndrome (type VI) harbor asymptomatic antiphospholipid antibodies. The relative frequency of ACLA in association with arterial and venous thrombosis strongly suggests that these should be looked for in any individual with unexplained thrombosis; all three idiotypes (IgG, IgA, and IgM) should be assessed. Also, the type of syndrome (I through VI) should be defined, if possible, as this may dictate both type and duration of both immediate and long-term anticoagulant therapy. Unlike those with ACLA, patients with primary lupus anticoagulant thrombosis syndrome usually suffer venous thrombosis. Because the activated partial thromboplastin time (aPTT) is unreliable in patients with lupus anticoagulant (prolonged in only about 40 to 50% of patients) and is not usually prolonged in patients with anticardiolipin antibodies, definitive tests including ELISA for ACLA, the dRVVT for lupus anticoagulant, hexagonal phospholipid neutralization procedure, and B-2-GP-I (IgG, IgA, and IgM) should be immediately ordered when suspecting antiphospholipid syndrome or in individuals with otherwise unexplained thrombotic or thromboembolic events. If these are negative, in the appropriate clinical setting, subgroups should also be assessed. Finally, most patients with antiphospholipid thrombosis syndrome will fail warfarin therapy and, except for retinal vascular thrombosis, most will fail antiplatelet therapy, thus it is of major importance to make this diagnosis in order that patients can be treated with the most effective therapy for secondary prevention, low-molecular weight heparin (LMWH) or unfractionated heparin (UHF) in most instances.     

Antiphospholipid antibody: functional specificity for inhibition of prothrombin activation by the prothrombinase complex

The antiphospholipid syndrome (APS) is associated with production of autoantibodies with lupus anticoagulant (LA) activity. These antibodies cause prolongation of in vitro clotting tests by inhibition of the conversion of prothrombin to thrombin in the presence of anionic phospholipid (PL). The extent to which this inhibition reflects antibody binding to, or functional inhibition of, phospholipids alone, prothrombin alone, or a prothrombin–phospholipid complex is pertinent to our understanding of the pathophysiology of this syndrome. Immunoglobulin fractions (IgG) from 18 patients with LA activity were tested for inhibitory activity against prothrombin activation by either factor Xa, in a purified prothrombinase system, or by purified fractions of snake venoms ( E. carinatus , E. multisquamatus ) which cleave prothrombin at the same initial site as the prothrombinase complex but do not require anionic phospholipid as a cofactor. Parallel testing of the same IgG samples for prothrombin binding by immunoassay was performed. Although all IgG samples inhibited the prothrombinase reaction, only three exhibited any inhibition of venom protease prothrombin activation in either the presence or absence of PL. Only one sample exhibited prothrombin binding by Western blot. These results suggest that lupus anticoagulant antibodies are heterogenous and that many, if not most, of the autoantibody populations responsible for LA activity impair prothrombin activation by interaction either with phospholipid alone or with a restricted range of prothrombin–phospholipid epitopes expressed by prothrombin only as part of the intact prothrombin–prothrombinase complex.     

A quarter of a century in anticardiolipin antibody testing and attempted standardization has led us to here, which is?

The anticardiolipin (aCL) test has been widely used by physicians since the mid-1980s for diagnosing patients with antiphospholipid syndrome (APS). Establishment of this diagnosis has enabled effective management of patients with recurrent thrombosis and recurrent pregnancy losses. The test was first established in 1983 as a radioimmunoassay and soon thereafter converted into an enzyme-linked immunosorbent assay (ELISA). The other test commonly used in the diagnosis of APS is the lupus anticoagulant (LA) test. The aCL ELISA is sensitive for the diagnosis of APS but lacks specificity. On the other hand, the LA assay, although more specific, is not as sensitive as the aCL ELISA. More specific tests are now available such as the anti-beta2 glycoprotein I (anti-beta2GPI) assay, the antiprothrombin assay, and other ELISAs that use negatively charged phospholipids instead of cardiolipin to coat the plates. In the past 25 years, there have been numerous efforts to standardize aCL, LA, and anti-beta2GPI tests but there are still reports of significant intra- and interlaboratory variation in results for all three assays. This article discusses in detail the clinical value of these tests, technical problems associated with their use, the current laboratory classification criteria for diagnosis of APS, and possible new and better assays that will be available in the near future for diagnosis of APS.     

Clinicohematologic spectrum in patients with lupus anticoagulant.

A retrospective analysis of clinicohematologic parameters of 25 patients with lupus anticoagulant was carried out. The hematologic tests included dilute Russel viper venom test (dRVVT), kaolin clotting time (KCT), activated partial thromboplastin time, and prothrombin time. The diagnosis of lupus anticoagulants was based on the presence of prolonged KCT/dRVVT, its absence of correction with normal plasma and correction by phospholipids. Specific factor assays and platelet aggregation studies were performed wherever required. Ten patients (40%) had thrombosis, which was venous in 5 (50%) and arterial in 4 (40%). One patient (10%) had both arterial and venous thrombosis and presented with catastrophic antiphospholipid syndrome. Eighteen female patients conceived. Four (22%) of these had recurrent first trimester abortion. Five (20%) patients had bleeding manifestations. One (4%) of these had hypoprothrombinemia and was diagnosed to have hypoprothrombinemia lupus anticoagulant syndrome. However in two of these patients, no cause of bleeding could be identified other than the presence of lupus anticoagulants. It is concluded that patients with lupus anticoagulant have a varied spectrum of hemostatic disorders. Bleeding may sometimes occur in these patients due to associated thrombocytopenia or associated factor inhibitors. Rarely, it may occur due to presence of lupus anticoagulants alone.     

Influence of hypergammaglobulinemia on antiphospholipid antibodies titres

PURPOSE: Antiphospholipid antibodies (aPL), anticardiolipin antibodies (aCL) or lupus anticoagulant (LA), are indispensable for the diagnosis of antiphospholipid syndrome (APS). However, antiphospholipid assays can generate false positive results. MATERIALS: We have studied the influence of hypergammaglobulinemia (HG) on aPL antibodies titers in 232 patients twice as positive for aPL antibodies. RESULTS: Out of 232 patients, 93 have an APS (76 primary APS, 17 secondary APS). Thrombosis occurred 138 times in APS patients. Of 139 patients without APS, 95 have an auto-immune disease, 28 have an isolated prolonged KCT and 16 an evolutive neoplasia. LA seems to be the best marker of APS. On the other hand aCL IgG and M, anti-beta2-GP1 IgM titers are significantly higher in patients without APS but with HG. CONCLUSION: Those results suggest that biological APS diagnosis should be carefully performed in patients with HG. In this case, other additional risk factors must be considered for the etiological diagnosis of thrombosis.     

'Non-criteria' aPL tests: report of a task force and preconference workshop at the 13th International Congress on Antiphospholipid Antibodies, Galveston, TX, USA, April 2010

Abstract: Current classification criteria for definite APS recommend the use of one or more of three positive standardized laboratory assays, including anticardiolipin antibodies (aCL), lupus anticoagulant (LA), and antibodies directed to β(2)glycoprotein I (anti-β(2)GPI) to detect antiphospholipid antibodies (aPL) in the presence of at least one of the two major clinical manifestations (i.e., thrombosis or pregnancy morbidity) of the syndrome. Several other autoantibodies shown to be directed to phospholipids and/or their complexes with phospholipids and/or to proteins of the coagulation cascade, as well as a mechanistic test for resistance to annexin A5 anticoagulant activity, have been proposed to be relevant to APS. A task force of worldwide scientists in the field discussed and analyzed critical questions related to 'non-criteria' aPL tests in an evidence-based manner during the 13th International Congress on Antiphospholipid Antibodies (APLA 2010, 13-16 April 2010, Galveston, Texas, USA). This report summarizes the findings, conclusions, and recommendations of this task force.     

Lupus anticoagulants in children

Lupus anticoagulant and ACAs are made up of heterogeneous IgG and IgM antibodies that prolong in vitro clotting times and are associated with increased risks of venous and arterial thrombosis, recurrent fetal loss, and autoimmune thrombocytopenia and anemia. These clinical findings with the appropriate laboratory results make up the antiphospholipid antibody syndrome. The antiphospholipid antibodies found in this syndrome are directed against a variety of phospholipid binding proteins of which beta2-glycoprotein and prothrombin are considered to be common antigens. Children who present with thrombosis and are positive for lupus anticoagulant and ACAs have similar clinical presentations and prognoses as adults. Isolated lupus anticoagulant and ACAs in children who are asymptomatic likely do not lead to clinical complications and are transient.     

The Russell viper venom time (RVVT) test for investigation of lupus anticoagulant (LA)

Lupus anticoagulants (LAs) are a laboratory representation of the clinical syndrome of antiphospholipid syndrome (APS), and can also arise in other pathological states. Laboratory testing for LA is complex and three separate recent guidelines have been published. One test, the Russell viper venom time (RVVT), is the mandated laboratory test for inclusion in LA identification/exclusion in all three guidance documents. This is because the the RVVT is recognized to have great sensitivity for LA, with this generally recognized to be greater than that of most other LA screening assays. However, the RVVT is also very sensitive to the presence of many anticoagulant drugs, which diminishes its specificity for LA. Various strategies can be used to improve LA specificity and reduce anticoagulant assay interference.     

Apport de la détection des anticorps antiphosphatidylsérine/prothrombine (aPS/PT) dans le diagnostic et la prise en charge du syndrome des antiphospholipides (SAPL)

Antiphospholipid syndrome (APS) is an autoimmune disease and one of the most common causes of acquired thrombophilia. It is characterised by the occurrence of thrombotic or obstetric events associated with the presence of persistent antiphospholipid antibodies. The diagnosis can be challenging, particularly because some biological tests can be disturbed by anticoagulant treatment or inflammation.In the recent years, new antiphospholipid antibodies, including anti-phosphatidylserine/prothrombin antibodies (anti-PS/PT), have emerged but their clinical significance and causality remain uncertain.Biologically, several studies have found a strong correlation between the presence of lupus anticoagulant (LA) and anti-PS/PT antibodies. Clinically, the presence of anti-PS/PT antibodies is associated with an increased risk of thrombosis and obstetric complications. There is also an association with thrombocytopenia, suggesting that the presence of anti-PS/PT antibodies may be associated with more severe clinical APS. Among seronegative APS patients, 6–17% of patients are positive for anti-PS/PT antibodies. This might influence the therapeutic management of patients.This article aims to provide an update on contribution of anti-PS/PT antibodies detection for the diagnosis and management of APS.     

Antiphospholipid antibodies and haemostasis

The antiphospholipid syndrome is characterized by recurrent thrombosis and pregnancy morbidity in association with the persistent presence of autoantibodies called antiphospholipid antibodies. Antiphospholipids are a heterogeneous group of circulating autoantibodies associated with a risk of thrombosis and can paradoxically prolong in vitro the clotting times. In the past few years, significant improvement has been made in understanding the pathophysiologic mechanisms of the disease, thus raising the possibility of future predictive test for the risk of thrombosis. The aim of this review is to make an overview on how the antiphospholipids increase the risk of thrombosis and to provide an update of the laboratory diagnosis and the possible future therapies.     

Impaired catalytic function of activated protein C: a new in vitro manifestation of lupus anticoagulant

Lupus anticoagulant (LA), an antibody against anionic phospholipid with anticoagulant laboratory manifestations, is paradoxically associated with a high incidence of thrombosis. In the present study we analyzed the phospholipid- and platelet-dependent degradation of factor Va following clotting in plasma from 15 consecutive patients with LA to provide evidence for a distinct procoagulant effect of the antibody. After clotting with 25 micrograms phospholipid/mL, all samples containing LA showed markedly decreased rates of factor Va degradation (k = 0.01 to 0.14 min-1 v 0.27 to 0.35 min-1 in controls). Also with higher phospholipid concentrations (up to 100 micrograms/mL), as well as in the presence of platelets (5 to 33 x 10(7)/mL), significantly less of the procoagulant activity disappeared per unit of time in samples with LA than in controls. Plasma with LA was to a variable extent capable of decreasing or abolishing factor Va inhibition in normal plasma. Most importantly, exogenous activated protein C failed to correct the ineffective factor Va destruction despite adequate protein S levels. These data suggest that LA prevents the formation of the complex essential for rapid proteolysis of factor Va both on phospholipid and on the platelet membrane, thereby compromising the catalytic function of activated protein C. Our findings offer a new opportunity for a more comprehensive evaluation of patients with antiphospholipid antibody in defining the pathogenesis of thrombosis in this clinical condition.     

A report on the First International Workshop for Lupus Anticoagulant Identification.

Recognition that the lupus anticoagulant (LA) is associated with an increased risk for arterial and venous thrombosis, recurrent spontaneous abortions and fetal loss has led to increased laboratory requests for identification of LA. It is of interest not only to laboratory medicine and obstetrics but also to rheumatology, neurology and cardiology. Due to the antibody's heterogeneous expression, no single test confirms its presence. Recent criteria for LA identification include the performance of one or more screening tests to demonstrate LA interference with phospholipid-dependent tests, differential studies to determine the presence of an inhibitor, and confirmatory procedures to prove that the inhibitor is phospholipid dependent. An international workshop was conducted to study a panel of tests for LA identification and to select those most helpful for diagnosis.     

Primary antiphospholipid syndrome: a cause of fever of unknown origin

Antiphospholipid syndrome (APS) is defined as the occurrence of thrombosis, recurrent miscarriage, or both in association with laboratory evidence of persistent antiphospholipid antibodies. Owing to protean manifestations and laboratory studies, the diagnosis may be difficult. Because the other signs and symptoms of thrombosis are predominant, prolonged fever is not usually the main clinical finding. We describe a patient who presented with fever of unknown origin (FUO) and was found to have thromboses of the splenic vein, the superior mesenteric vein, and the portal vein due to the primary antiphospholipid syndrome. We also reviewed the medical literature (Medline 1966-2001), including the main FUO series of the previous 40 years, and laparotomy series for FUO. We conclude that although very rare, primary APS and thrombosis may present with FUO. APS should be considered in the differential diagnosis of prolonged fever associated with thrombosis.