The Risk of Thrombosis in Patients with Lupus Anticoagulants Is Predicted by their Specific Coagulation Profile

Viewpoint: The value of non-criteria antiphospholipid antibodies

In 2006, at a meeting in Sydney, Australia, consensus was reached by an international group of specialists to establish a number of serological criteria that identify patients with a history of thrombosis or pregnancy complications as having antiphospholipid syndrome (APS). These criteria were originally formulated for research purposes and to compare clinical trials in different centres. However, these same criteria are now generally used and accepted for the diagnosis and treatment of patients. The practice of using these criteria for direct patient care requires that these criteria are based on sound scientific evidence. Indeed, for all the autoantibodies that are officially included in the serological criteria, it has been shown that they induce thrombosis and fetal loss when infused into mice. There are also a number of additional autoantibodies that have been identified in these patients but for these antibodies there was not enough evidence to meet the official APS criteria in 2006. Seventeen years have now passed since the consensus meeting, therefore, this review examines whether additional studies performed with these 'non-criteria' autoantibodies have provided sufficient results to suggest the inclusion of these autoantibodies in the official serological criteria of APS.

Lupus Anticoagulant Positivity in Pediatric Patients With Prolonged Activated Partial Thromboplastin Time: A Single-Center Experience and Review of Literature

The presence of lupus anticoagulants (LAs) is an important cause of activated partial thromboplastin time (aPTT) prolongation found in children after an infection or during screening tests before surgical intervention. The authors retrospectively reviewed the charts of 68 patients who have been consulted from surgery departments with prolonged aPTT. These patients were reevaluated with aPTT analysis after 1 week. Thirteen patients had normal aPTTs. Therefore, 55 patients remained with prolonged aPTTs. LA positivity was detected in 39 patients. Sixteen of these had prolonged aPTT prior to surgery (41%). Others with LA positivity had systemic lupus erythematosus (SLE; n = 6), infection (n = 5), leukemia (n = 3), hemolytic uremic syndrome (n = 2), epistaxis (n = 2), antiphospholipid syndrome (APS; n = 1), chronic immune thrombocytopenic purpura (n = 1), acute poststreptococcal glomerulonephritis (n = 1), central nervous system (CNS) thrombosis (n = 1), and congenital heart disease (n = 1). None of the patients had bleeding history. LA positivity rarely leads to bleeding and/or thrombosis. Specific therapy is usually not needed. Further prospective multicenter studies are required to understand clinical outcomes and laboratory correlation in children with positive LA.

Laboratory methods to detect antiphospholipid antibodies

This chapter reviews several important themes pertaining to the antiphospholipid syndrome (APS), including a description of the clinical features, a discussion of the main autoantigen, beta 2-glycoprotein I (β2GPI), and insights into the characteristics of the pathogenic anti-β2GPI autoantibodies. Evidence-based considerations for when to test for APS are explored, along with the clinical significance of patients testing positive on multiple APS assays, so-called triple positivity. A detailed review of recently published laboratory guidelines for the detection of lupus anticoagulant and the solid-phase anticardiolipin and anti-β2GPI ELISAs is undertaken. Finally, a brief review of nonclassification criteria laboratory assays with potential future diagnostic utility is presented.

Task Force on Catastrophic Antiphospholipid Syndrome (APS) and Non-criteria APS Manifestations (II): thrombocytopenia and skin manifestations

The objectives of the ‘Task Force on Catastrophic Antiphospholipid Syndrome (APS) and Non-criteria APS Manifestations’ were to assess the clinical utility of the international consensus statement on classification criteria and treatment guidelines for the catastrophic APS, to identify and grade the studies that analyze the relationship between the antiphospholipid antibodies and the non-criteria APS manifestations, and to present the current evidence regarding the accuracy of these non-criteria APS manifestations for the detection of patients with APS. This article summarizes the studies analyzed on thrombocytopenia and skin manifestations, and presents the recommendations elaborated by the Task Force after this analysis.

Antiphospholipid-associated thrombocytopenia or autoimmune hemolytic anemia in patients with or without definite primary antiphospholipid syndrome according to the Sapporo revised classification criteria: a 6-year follow-up study

The updated Sapporo classification criteria for antiphospholipid syndrome (APS) only include thrombosis or pregnancy morbidity as clinical criteria. To test this notion, we studied 55 patients (80% women) with hematologic manifestations. All fulfilled the laboratory criteria for primary APS. Thirty-five patients (64%) had thrombocytopenia, 14 (25%) had autoimmune hemolytic anemia, and 6 (11%) had both. Twenty-five patients (22 women, 88%) also fulfilled one clinical criterion for APS after a median follow-up of 13.2 years (range, 1.45-37 years), whereas the remaining 30 patients (22 women, 73%) have not had any thrombotic event nor pregnancy morbidity after a median follow-up of 5.4 years (range, 0.12-24 years). No patient developed systemic lupus erythematosus during follow-up. The hematologic manifestation was asynchronous with the APS onset in 84% of patients. The response to treatment was similar regardless of the APS status. Patients with definite APS were more frequently positive for the lupus anticoagulant (63%) than lupus anticoagulant-positive patients without APS (30%; odds ratio, 3.5; 95% confidence interval, 1.07-11.4; P < .02). Anticardiolipin or anti–β2-glycoprotein-I antibodies were highly prevalent among the study groups. Our study suggests that, depending upon their antiphospholipid profile, patients with hemocytopenias appear to comprise a peculiar subset of patients with APS; some develop thrombotic and/or obstetric APS whereas others continue with hematologic APS.

Screening for lupus anticoagulant: improving the performance of the lupus-sensitive PTT-LA

INTRODUCTION

The aim of the present work was to verify whether calculating a ratio between clotting times obtained with the sensitive PTT-LA and a less sensitive activated partial thromboplastin time (aPTT)-reagent may represent a valuable aPTT-based screening strategy for lupus anticoagulants (LA).

METHODS

For the pilot study, plasma samples from normal subjects (n = 15) and from patients with LA (n = 10), therapeutic anticoagulation with vitamin K-antagonists (VKA) (n = 15) or unfractionated heparin (n = 15), coagulation factors deficiency (n = 16), and inhibitory antibodies against factor VIII or IX (n = 11) were studied. For the evaluation study, 1553 consecutive plasma samples from nonanticoagulated patients investigated for LA between January 2005 and December 2007 at our institution were studied. Following screening strategies were employed: Pathromtin-SL (aPTT-SL), PTT-LA (aPTT-LA), ratio aPTT-LA/aPTT-SL (aPTT-ratio), and Russell's viper venom (RVV) based LA-Check. LA positive samples were identified by mixing studies and diluted RVV confirmation test (LA-Check/LA-Sure).

RESULTS

Pilot study: All screening strategies had a 100% sensitivity, and the aPTT-ratio reached the highest specificity (82%; 95%CI: 74-90%). Within the evaluation study, following sensitivities for LA screening were observed: aPTT-SL 59.0% (95%CI: 57-61%), aPTT-LA 82.1% (95%CI: 80-84%), aPTT-ratio 92.3% (95%CI: 91-94), and LA-Check 83.3% (95%CI: 82-85%).

CONCLUSION

Calculating a ratio between the LA-sensitive PTT-LA and the less sensitive Pathromtin-SL improves the performance of the PTT-LA itself and represents a simple and sensitive aPTT-based integrated strategy for LA screening.

Survey of lupus anticoagulant diagnosis by central evaluation of positive plasma samples

OBJECTIVE

To determine whether the diagnosis of lupus anticoagulant (LAC) in a large cohort of positive patients was confirmed at a reference laboratory.

METHODS

Over a 1-year period, each participating center collected samples from LAC-positive patients. Plasma was filtered and kept deep-frozen until it was sent on dry ice to the reference laboratory by express courier. Centers returned detailed laboratory information and clinical data from each patient. The reference laboratory screened plasma samples by diluted Russell viper venom time (dRVVT) and kaolin clotting time (KCT). When these were prolonged, 1:1 mixing studies were carried out, and confirmatory tests were performed as appropriate. Positive samples were further tested by thrombin time (TT). The presence of heparin was checked by measuring antifactor Xa activity when TT was prolonged. Negative samples were tested by activated partial thromboplastin time using hexagonal phospholipids.

RESULTS

Plasma samples from 302 patients from 29 anticoagulation clinics were analyzed. LAC was excluded in 71 samples (24%), because dRVVT and KCT screening test results were normal (34) or reversed to normal by mixing studies (35). The remaining two samples were considered negative because they contained heparin. LAC-negative patients showed different characteristics from those in whom diagnosis was confirmed. They were significantly older (49.7 vs. 45.0 years, P < 0.03), were more often first diagnosed (66% vs. 41%, P < 0.001), and were more frequently judged as mild in LAC potency (60% vs. 25%, P < 0.0001). Moreover, anticardiolipin and anti-beta(2)-glycoprotein I antibody values were more often normal in LAC-negative (82%) than in LAC-positive (42%) samples (P < 0.0001). LAC-positive samples identified by both dRVVT and KCT (146/231, 63%) showed a LAC potency that was significantly stronger than that in samples in which LAC diagnosis was made by a single test.

CONCLUSIONS

A false-positive LAC diagnosis is not uncommon across specialized centers. Patients' characteristics and a complete antiphospholipid antibody profile may help to identify these individuals.

Use of a new silica clotting time for diagnosing lupus anticoagulant in patients who meet the clinical criteria for antiphospholipid syndrome

The silica clotting time (SCT) is a phospholipid-dependent coagulation assay used for the laboratory diagnosis of lupus anticoagulant (LA) antibodies. The sensitivity and specificity of a new commercial SCT for identifying LA in patients who meet the clinical criteria for antiphospholipid syndrome (APS), and its association with thrombotic events were evaluated here. Forty-five patients who met the clinical criteria for APS according to the Sapporo International Consensus Statement were examined. Sixty-nine patients who did not meet the clinical criteria for APS, and 20 blood donors were used as controls. Plasma samples from the patients and controls were tested for LA using a new commercial SCT with low and high synthetic phospholipid concentrations. The results were compared with those obtained by diluted Russell's viper venom time (dRVVT) and activated partial thromboplastin time (APTT). SCT's sensitivity for identifying LA in patients who met the clinical criteria of APS was higher compared to APTT and dRVVT (53.3% vs. 31.1% and 31.1%), and the specificities of these assays were 96.6%, 100%, and 98.9%, respectively. When dRVVT was combined with SCT, and dRVVT was combined with APTT their sensitivities were 57.7% and 48.8%, and their specificities were 96.6% and 98.9%, respectively. A stepwise logistic regression analysis indicated that the combination of dRVVT with SCT was associated with total thrombotic events (odds ratio (OR)=11.5, 95% confidence interval (CI)=1.25-106.3, P=0.031) as well as with venous thrombosis (OR=4.09, 95% CI=1.16-14.43, P=0.028). According to our results, SCT is the most sensitive assay for identifying LA in patients who meet the clinical criteria for APS. Moreover, the highest sensitivity was reached with a combination of SCT and dRVVT. The method's association with total thrombotic events and venous thrombosis was in fact significant.

A prospective study of antibodies to beta2-glycoprotein I and prothrombin, and risk of thrombosis

Antiphospholipid syndrome (APS) is a clinical autoimmune disorder characterized by thrombosis/pregnancy morbidity associated with the persistence of lupus anticoagulant (LA) and/or anticardiolipin (aCL) antibodies. We assessed the contribution of antibodies to beta2-glycoprotein I (anti-beta2GPI) and prothrombin (anti-PT) to the thrombotic risk in a cohort of 194 consecutive patients with persistent LA and/or aCL. Median follow-up was 45 months. A total of 39 patients (20.1%) had one documented episode of thrombosis during follow-up. Eleven of these patients had no previous thrombosis before enrollment in the study and 28 had recurrences of thrombosis. There were 21 venous and 18 arterial thrombotic events and the overall incidence of thrombosis was 5.6% per patient-year. After multivariate analysis, the male sex (P = 0.025), a previous thrombosis (P < 0.01), the presence of anti-beta2GPI (P = 0.001), and the presence of anti-PT (P = 0.03) remained as independent risk factors for recurrent thrombosis. Only IgG anti-beta2GPI and anti-PT were associated with an increased risk of thrombosis (P < 0.01 and P = 0.005). Patients testing positive for anti-beta2GPI had a higher rate of thrombosis than did antiphospholipid patients without anti-beta2GPI (8.0% vs. 3.1% per patient-year). Similarly, a higher rate of thrombosis was found in patients with positive anti-PT compared with patients without anti-PT (8.6% vs. 3.5% per patient-year). Considering only the group of 142 LA positive patients, the highest incidence of thrombosis was found in LA patients positive for both anti-beta2GPI and anti-PT (8.4% per patient-year). In conclusion, the presence of IgG anti-beta2GPI and anti-PT in patients with LA and/or aCL and mainly in those with LA predicts a higher risk of thromboembolic events.

Antiphospholipid antibodies and thrombosis: do test patterns identify the patients' risk?

We retrospectively analyzed the antiphospholipid profile of 103 lupus anticoagulant-positive patients to investigate whether laboratory patterns emerged for their association with arterial and venous thrombosis in the antiphospholipid syndrome. Anticardiolipin, anti-<beta>2-glycoprotein I and antiprothrombin antibodies were combined with coagulation tests in different patterns, which included from 2 to 5 laboratory variables. Overall, 22 out of 180 available associations reached significance: 14 with any type of thrombosis and eight with venous thrombosis. In all but two cases, anticardiolipin antibodies>40 units were present in the laboratory patterns that reached significance. Anti-<beta>2-glycoprotein I antibodies were present in 11 significant patterns, and antiprothrombin antibodies in seven cases. Increasing the number of variables of the laboratory patterns did not increase the odds ratio (OR) towards thrombosis. In conclusion, this analysis confirmed that the presence of IgG anticardiolipin antibodies at medium to high titres, either alone or in various combinations with other tests, is clinically useful to establish the patients' risk of thrombosis. The role of the other antiphospholipid antibodies is less clear.

Antiphospholipid syndrome: association between laboratory tests and clinical practice

Antiphospholipid antibodies are a wide and heterogeneous group of immunoglobulins, whose presence inpatients with arterial and venous thrombosis, and obstetrical complications defines the antiphospholipid syndrome. We systematically reviewed published articles on this syndrome to investigate the association between thrombosis and the most common antiphospholipid antibodies. Lupus anticoagulants were a clear risk factor for thrombosis, irrespective of the site and type of thrombosis, the presence of systemic lupus erythematosus, and the methods used to detect them. Anticardiolipin and anti 2-glycoprotein I antibodies were possible risk factors of thrombosis, at least in some selected situations. Conversely, the measurement of antiprothrombin antibodies was not helpful to define the patient's risk of thrombosis. These results are mainly due to the still far from optimal standardization of the methods to detect the various antiphospholipid antibodies.

Acquired Activated Protein C Resistance Associated with IgG Antibodies against β2-Glycoprotein I and Prothrombin as a Strong Risk Factor for Venous Thromboembolism

Background: Venous thromboembolic events such as deep vein thrombosis and pulmonary embolism are common manifestations of antiphospholipid syndrome. Our aim was to clarify the roles of anti-phospholipid (aPL) antibodies in the pathogenesis of venous thromboembolism (VTE) in patients with systemic lupus erythematosus (SLE).

Methods and Results: We examined anti-cardiolipin/β2-glycoprotein I (anti-CL/β2-GPI) antibody concentrations, anti-phosphatidylserine/prothrombin (anti-PS/PT) antibody concentrations, and lupus anticoagulant (LA) activity in 87 patients with SLE (21 with VTE and 66 without thrombosis). Both anti-CL/β2-GPI and anti-PS/PT antibodies strongly correlated with LA activity. Multivariate logistic analysis confirmed that both anti-CL/β2-GPI and anti-PS/PT antibodies were significant independent risk factors for VTE (odds ratios = 4.98 and 7.54, respectively; 95% confidence intervals, 1.51–16.4 and 2.30–24.7, respectively). We therefore studied the in vitro effects of IgG fractions containing anti-CL/β2-GPI or anti-PS/PT antibodies on the anticoagulant activity of activated protein C (APC) and found that purified IgG containing anti-CL/β2-GPI or anti-PS/PT antibodies significantly hampered the anticoagulant activity of APC. We also studied the ability of IgG fractions to impede the anticoagulant activity of APC before and after complete removal of anti-CL/β2-GPI or anti-PS/PT antibodies by adsorption. Removal of anti-CL/β2-GPI or anti-PS/PT antibodies from all positive IgG samples clearly decreased the inhibitory effect of those samples on APC anticoagulant activity.

Conclusions: Anti-CL/β2-GPI and anti-PS/PT antibodies independently cause APC resistance, which may contribute to risk of VTE in patients with SLE.

Exercise-induced activation of coagulation in subjects with activated protein C resistance

In the healthy individual intensive physical exercise leads to a minor activation of blood coagulation that appears to be balanced by a concomitant activation of the fibrinolytic system. This study tested the hypothesis that vigorous exercise might give rise to an exaggerated activation of coagulation in subjects with resistance to activated protein C (APC). Molecular markers of thrombin (prothrombin fragment 1 + 2, thrombin-antithrombin III complexes) and fibrin formation (fibrinopeptide A), as well as markers of the fibrinolytic activity (plasmin-antiplasmin complexes, D-dimers), were determined in nine asymptomatic male individuals with APC resistance [age, 18 +/- 3 years; maximal oxygen consumption, 56.7 +/- 2.7 ml/kg per min (mean +/- standard deviation)] and in nine male control subjects (age, 19 +/- 4 years; maximal oxygen consumption, 56.2 +/- 3.2 ml/kg per min) after 1 h of running to exhaustion. Baseline levels of prothrombin fragment 1 + 2 were higher in individuals with APC resistance than in controls [0.67 +/- 0.06 nmol/l (mean +/- standard error) versus 0.48 +/- 0.01 nmol/l; P < 0.05]. In response to exercise, hemostatic variables significantly increased in both groups to a similar small extent. Likewise, exercise-induced changes of fibrinolytic variables in subjects with APC resistance paralleled those observed in controls. In summary, exhaustive running in subjects with APC resistance does not provoke an abnormal hemostatic or fibrinolytic response, suggesting that vigorous exercise does not imply an increased risk for thrombosis in young male subjects with APC resistance.

Étude de l'influence d'une hypergammaglobulinémie sur le titre des anticorps antiphospholipides

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.

Lupus Anticoagulant (LA) Testing: Performance of Clinical Laboratories Assessed by a National Survey Using Lyophilized Affinity-purified Immunoglobulin with LA Activity

Background: Lupus anticoagulant (LA) screens are frequently ordered in the workup of thrombophilic patients or women with fetal loss. The sensitivity and specificity of LA detection vary depending on the choice of tests, cutoff values, and results interpretation. This variation is detrimental to patient management because persistent LA positivity in patients with a history of thrombosis is a requisite for long-term anticoagulation therapy. Numerous surveys have been performed to assess the state of the art for LA diagnosis. The control plasmas used in these surveys were from LA-positive or -negative patients or were normal plasmas with monoclonal antibodies against human β2-glycoprotein I (β2-GPI) added.

Methods: A large number of laboratories were asked to test a common set of lyophilized plasmas for LA, including three normal plasmas, to which increasing amounts of affinity-purified IgG from a patient positive for anti-β2-GPI had been added, and three LA-negative plasmas: one normal, one with a coagulation deficiency, and one with heparin.

Results: Overall, 69, 68, and 59 of 70 participants were able to detect LA in plasmas with high, intermediate, and low potency (sensitivity, 99%, 97%, and 84%). Conversely, 69, 50, and 53 of 70 were able to rule out LA in the normal, heparinized, and deficient plasma (specificity, 99%, 71%, and 76%).

Conclusions: Sensitivity for LA detection is satisfactory, whereas specificity could be improved. Surveys for LA detection should be carried out on a regular basis because they may help improve performance. Plasmas containing graded amounts of affinity-purified human anti-β2-GPI may be used as a convenient source of well-characterized naturally occurring LA material.

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.

Clinical significance of acquired activated protein C resistance in patients with systemic lupus erythematosus

Antiphospholipid antibodies (aPL) may induce acquired activated protein C resistance (acquired APCR). The role of acquired APCR in patients with systemic lupus erythematosus (SLE) is not well known. To evaluate the prevalence of acquired APCR and its association with clinical manifestations we studied 103 consecutive SLE patients and 103 matched controls. APCR in the undiluted test and after dilution in factor V deficient plasma, factor V Leiden, protein C and S, lupus anticoagulant, and anti-cardiolipin, anti-beta2-glycoprotein I and anti-prothrombin antibodies were determined. Factor V Leiden was found in 4% in both patients and controls. The prevalence of acquired APCR was 22% for the undiluted assay and 17% in the diluted test. In SLE patients, acquired APCR was associated with aPL (39 vs 13% in undiluted assay, P = 0.007; and 33 vs 7% in the diluted test, P = 0.001). Arterial thromboses were found in 24% of patients with acquired APCR and in 6% of patients without (P = 0.04). However, no relationship was found with venous thrombosis. Acquired APCR was also associated with pregnancy losses: miscarriages in 70% of women with acquired APCR vs 32% in those without (P=0.03). Thus, in SLE patients acquired APCR seems to be associated with increased prevalence of arterial thrombosis and pregnancy losses.

Current status and implications of autoimmune antiphospholipid antibodies in relation to thrombotic disease

This review briefly describes the development of the concepts of antiphospholipid antibody and of antiphospholipid syndrome. It focuses on the two main antigenic targets, beta2 glycoprotein I and prothrombin. An excessive production of natural antibodies rather than an immune response to exogenous antigen is proposed as pathogenetic for the development of these antibodies. The review attempts to explain how some of these antibodies are anticoagulant in vitro yet prothrombotic in vivo. The final section discusses when to test for such antibodies, how to test and how to consider treatment of patients with the antiphospholipid syndrome.

Lupus anticoagulants are stronger risk factors for thrombosis than anticardiolipin antibodies in the antiphospholipid syndrome: a systematic review of the literature

To formally establish the risk of lupus anticoagulants and anticardiolipin antibodies for arterial and venous thrombosis, we ran a MEDLINE search of the literature from 1988 to 2000. Studies were selected for their case-control (11), prospective (9), cross-sectional (3), and ambispective (2) design. They provided or enabled us to calculate the odds ratio with 95% confidence interval (CI) of lupus anticoagulants and/or anticardiolipin antibodies for thrombosis in 4184 patients and 3151 controls. Studies were grouped according to the antibody investigated. Five studies compared lupus anticoagulants with anticardiolipin antibodies: the odds ratio with 95% CI of lupus anticoagulants for thrombosis was always significant. None of them found anticardiolipin antibodies were associated with thrombosis. Four studies analyzed only lupus anticoagulants: the odds ratio with 95% CI was always significant. The risk of lupus anticoagulants was independent of the site and type of thrombosis, the presence of systemic lupus erythematosus, and the coagulation tests employed to detect them. Sixteen studies served to assess 28 associations between anticardiolipin antibodies and thrombosis: the odds ratio with 95% CI was significant in 15 cases. Anticardiolipin titer correlated with the odds ratio of thrombosis. In conclusion, the detection of lupus anticoagulants and, possibly, of immunoglobulin G (IgG) anticardiolipin antibodies at medium or high titers helps to identify patients at risk for thrombosis. However, to take full advantage of the conclusions provided by the available evidence, there is an urgent need to harmonize investigational methods.

Antiphospholipid antibodies and antiphospholipid syndrome in patients presenting with immune thrombocytopenic purpura: a prospective cohort study

The pathogenetic role and the clinical importance of the presence of antiphospholipid antibodies (APAs) in patients with immune thrombocytopenic purpura (ITP) are not clear. In this study, the prevalence and clinical significance of APAs were investigated in patients with ITP. Eighty-two newly diagnosed ITP patients were prospectively studied. They were evaluated for the presence of lupus anticoagulant (LA) and immunoglobulin G/M anticardiolipin antibodies (ACAs). Thirty-one patients (37.8%) were APA positive at diagnosis. No statistically significant differences were found between the APA-positive and APA-negative groups regarding gender, initial platelet counts, or response to methylprednisolone therapy. After 5 years of follow-up, cumulative thrombosis-free survival of APA-positive (n = 31) and APA-negative (n = 51) ITP patients was 39% and 97.7%, respectively. A significant difference was found between these groups by log-rank test (P =.0004). In addition, LA was an important risk marker for the development of thrombosis in ITP patients. After a median follow-up of 38 months, 14 ITP patients (45%) who had APA positivity developed clinical features (thrombosis or fetal losses) of antiphospholipid syndrome (APS). There were no differences between the APA-positive patients with and without APS regarding the initial platelet counts, response to the therapy, or ACA positivity. The positivity rate for LA was significantly higher in those patients with ITP who developed APS (chi(2): P =.0036; relative risk 7.15; 95% confidence interval, 1.7-47). In conclusion, this study indicates that a significant proportion of patients initially presenting with ITP and APA positivity developed APS. In patients with ITP, the persistent presence of APAs is an important risk factor for the development of APS.

Anti-prothrombin antibodies combined with lupus anti-coagulant activity is an essential risk factor for venous thromboembolism in patients with systemic lupus erythematosus

Anti-prothrombin antibodies (anti-prothrombin) and anti-beta2-glycoprotein I antibodies (anti-beta2-GP I) are the most common and characterized anti-phospholipid antibodies (aPL) detected using specific enzyme-linked immunosorbent assay (ELISA) systems. Recently, lupus anti-coagulant (LA) activity detected by a phospholipid-dependent coagulation assay was reported to be associated with anti-prothrombin and/or anti-beta2-GP I. Here we show that the co-existence of IgG anti-prothrombin and LA activity might be an essential risk factor for venous thromboembolism (VTE) in patients with systemic lupus erythematosus (SLE). We examined not only the levels of antibodies to prothrombin and anti-beta2-GP I (both IgG and IgM isotypes) using an ELISA system, but also LA activity detected using both diluted Russell's viper venom time (dRVVT) and STACLOT LA test in 124 patients with SLE. The SLE patients were divided into four groups according to the results of ELISA and LA assay results for each aPL: group A, ELISA+ and LA+ group B, ELISA+ and LA-; group C, ELISA- and LA+ group D, ELISA- and LA-. Regarding IgG anti-prothrombin, the prevalence of VTE was significantly higher in group A (16/35 cases, 45.7%, P < 0.001, Fisher's exact probability test) than in the other groups (B, 2/30, 6.7%; C, 1/22, 4.5%; D, 1/37, 2.7%). With respect to IgM anti-prothrombin and IgG or IgM anti-beta2-GP I, the prevalence of VTE was higher in both groups A and C than in group D, but no statistical difference in prevalence was found between groups A and C. Multivariate logistic regression analysis of risk factors for VTE confirmed that the co-existence of IgG anti-prothrombin and LA activity was the only significant risk factor for VTE (odds ratio, 19.13; 95% confidence intervals, 4.74-77.18).

The epidemiology of the antiphospholipid syndrome: who is at risk?

Arterial and venous thrombosis are the most common and clinically relevant events of the so-called antiphospholipid syndrome; they are reported in approximately one third of patients with the antiphospholipid (aPL) antibodies. APL antibodies are part of a wide family of immunoglobulins directed against proteins complexed with negatively charged phospholipids. They include lupus anticoagulants (LA), anticardiolipin (aCL) antibodies, and the most recently recognized anti-beta-2-glycoprotein I (beta 2-GPI) and antiprothrombin (aPT) antibodies. Previous thrombotic events and the presence of LA, particularly if identified by the dilute Russell viper venom test, appear to be the strongest risk factors for vascular complications. High-titer aCL antibodies have been reported to be associated with an increased thrombotic tendency, but this was not confirmed in all studies. The data only partially support the concept that anti-beta 2-GPI and aPT antibodies may be considered as independent risk factors for thrombosis. Further prospective studies are required.

As compared to kaolin clotting time, silica clotting time is a specific and sensitive automated method for detecting lupus anticoagulant

Lupus anticoagulants (LAs) are antiphospholipid antibodies capable of interfering with the coagulation system and modifying in vitro the phospholipid-dependent clotting tests. Colloidal silica was used as activator to perform an activated partial thromboplastin time (aPTT) in 73 plasma samples with pathologically elevated kaolin clotting time (KCT) values using a photooptical automated coagulometer. Samples were incubated for 5 min with micronized silica, and after recalcification, the clotting times were measured. Pathologically prolonged results were confirmed by a confirmation and a neutralization test adding platelet-poor normal plasma (PPNP) and natural phospholipids, respectively. Silica clotting time (SCT) was abnormally elevated in 72/73 (98.6%) (mean ratio 1.71 +/- 0.28) KCT positive samples and normalized (mean ratio 1.03 +/- 0.16) after adding natural phospholipids to test plasma. The values expressed as SCT and KCT ratios were significantly correlated (r = .92; P < .001). SCT was normal in 40 healthy subjects utilised as controls (mean ratio 0.99 +/- 12). Sensitivity, specificity and diagnostic accuracy of SCT were 98.6%, 100% and 97.6%, respectively. Our data suggest that SCT is a sensitive test for detecting LA with a prolonged KCT in automated photooptical coagulometers. This peculiarity makes it particularly useful, in combination with diluted Russel viper venom time (dRVVT), for large-scale screening tests on LA.

Diagnostic testing for coagulopathies in patients with ischemic stroke

BACKGROUND

Hypercoagulable states are a recognized, albeit uncommon, etiology of ischemic stroke. It is unclear how often the results of specialized coagulation tests affect management. Using data compiled from a systematic review of available studies, we employed quantitative methodology to assess the diagnostic yield of coagulation tests for identification of coagulopathies in ischemic stroke patients.

SUMMARY OF REVIEW

We performed a MEDLINE search to identify controlled studies published during 1966-1999 that reported the prevalence of deficiencies of protein C, protein S, antithrombin III, plasminogen, activated protein C resistance (APCR)/factor V Leiden mutation (FVL), anticardiolipin antibodies (ACL), or lupus anticoagulant (LA) in patients with ischemic stroke. The cumulative prevalence rates (pretest probabilities) and positive likelihood ratios for all studies and for those including only patients aged </=50 years were used to calculate posttest probabilities for each coagulopathy, reflecting diagnostic yield. The cumulative pretest probabilities of coagulation defects in ischemic stroke patients are as follows: LA, 3% (8% for those aged </=50 years); ACL, 17% (21% for those aged </=50 years); APCR/FVL, 7% (11% for those aged </=50 years); and prothrombin mutation, 4.5% (5.7% for those aged </=50 years). The posttest probabilities of ACL, LA, and APCR increased with increasing pretest probability, the specificity of the tests, and features of the patients' history and clinical presentation.

CONCLUSIONS

The pretest probabilities of coagulation defects in ischemic stroke patients are low. The diagnostic yield of coagulation tests may be increased by using tests with the highest specificities and by targeting patients with clinical or historical features that increase pretest probability. Consideration of these data might lead to more rational ordering of tests and an associated cost savings.

Conceptions and misconceptions in testing for lupus anticoagulants

The aim of the following presentation is to review certain technical issues complicating clotting tests for lupus anticoagulants (LA). This is a field riddled with incorrect and misleading studies which often make progress difficult and which are difficult to retract. Inconsistent test sensitivity comparisons are sometimes due to incorrect methods being used but are more often due to contamination with platelets and instrument effects. Time dependence of LA is often due to pH drift during incubation and probably all LA are immediate acting (at least in our hands). The use of platelets in confirmatory tests is dangerous and can lead to false-positive results in patients with anti-factor V and heparin-like inhibitors.

Update on antiphospholipid antibodies

The association of antibodies with an apparent specificity for anionic phospholipids with thrombosis, fetal loss, thrombocytopenia, and certain other clinical manifestations is now well-recognized as the antiphospholipid syndrome (APS). Recent advances in our understanding of the antibodies and antigens involved include discovery of the crystal structure of beta2-glycoprotein I, (beta2GPI), genetic studies of beta2GPI polymorphisms, and the development of anti-beta2GPI and antiprothrombin immunoassays as clinical laboratory tests. The identification of antigen-specific T cells in APS patients has stimulated interest in the role of the cellular immune response in the syndrome. Clinical research in APS will also benefit from the development of preliminary classification criteria.

Which are the best biological markers of the antiphospholipid syndrome?

The diagnosis of antiphospholipid syndrome (APS) requires the presence of both clinical and biological features. Due to the heterogeneity of anti-phospholipid antibodies (aPL) the laboratory approach for their detection includes clotting-based tests for lupus anticoagulant (LA) as well as solid-phase assays for anticardiolipin antibodies (aCL). In addition, as it has been shown that autoimmune aPL recognize epitopes on phospholipid (PL)-binding plasma proteins, assays detecting antibodies to beta 2-glycoprotein I (beta 2-GPI) or prothrombin have been developed. The association between venous or arterial thrombosis and recurrent fetal loss with the presence of conventional aPL (LA and/or aCL) has been confirmed by many studies. The LA and IgG aCL at moderate/high titre seem to exhibit the strongest association with clinical manifestations of the APS. Several reports indicate that LA is less sensitive but more specific than aCL for the APS. Assays against PLs other than CL as well as the use of mixtures of PLs have been proposed to improve the detection of APS-related aPL. Concerning antibodies to PL-binding proteins (detected in the absence of PLs), there is evidence that anti-beta 2-GPI are closely associated with thrombosis and other clinical features of the APS. Moreover, these antibodies may be more specific in the recognition of the APS and in some cases may be present in the absence of aPL detected by standard tests. Many issues are still under debate and are discussed in this review, such as the problems of standardization of anti-beta 2-GPI assays, detection of the IgA isotype of aCL and anti-beta 2-GPI, the coagulation profiles of LA in the recognition of the thrombotic risk and the association of particular markers with subsets of patients with APS.

Antiphospholipid syndrome: antibodies and antigens

Elucidation of the antibodies and antigens involved in the antiphospholipid syndrome has provided many new insights and research opportunities. The major autoantibodies associated with the syndrome and detected in clinical laboratory assays for antiphospholipid antibodies are directed against prothrombin and beta2-glycoprotein I beta2GPI), a phospholipid-binding plasma protein whose physiological function is unknown. Recent advances in our understanding of these antibodies and antigens include discovery of the crystal structure of beta2GPI, identification of a plasmin cleavage site in beta2GPI, genetic studies of beta2GPI polymorphisms, development of clinical laboratory assays using purified protein antigens, and the identification of antigen specific T cells.

The anti-phospholipid antibody syndrome: clinical and serological aspects

The association of thromboses and/or cytopenias with anti-phospholipid antibodies (aPL), the anti-phospholipid syndrome (APS), is well recognized. The syndrome may be primary or occur within systemic lupus erythematosus (SLE). The notion of the syndrome occurring within SLE is important since patients found to have aPL may be at risk for developing APS manifestations, those who develop some manifestations may be at risk for developing others and, finally, SLE patients with this syndrome may need special treatment. There are subtle differences between the primary and the secondary forms, mostly due to the frequently higher and more persistent autoantibody levels in the primary and the influence of lupus in the secondary. These syndromes may be related to various antigen/antibody systems in which phospholipids participate either directly or through their effect on the proteins that bind them. Similar clinical manifestations also occur in patients who have serum antibodies to such proteins (e.g. beta2-glycoprotein-I) in the absence of phospholipid. Some of these antibodies may even be more important pathogenically than the antibodies against cardiolipin that were originally described. Testing for the latter is, however, still the first choice when suspecting an antiphospholipid syndrome. If this is negative in this situation, a search for the other autoantibodies is indicated.

High levels of antiphospholipid antibodies are associated with cytomegalovirus infection in unrelated bone marrow and cord blood allogeneic stem cell transplantation

Antiphospholipid antibodies (APA) are a family of autoimmune and alloimmune immunoglobulins recognizing protein-phospholipid complexes in in vitro laboratory test systems. These antibodies have been associated with several conditions (malignancies, autoimmune diseases, infections, use of drugs); moreover, a syndrome capable of inducing thromboembolic disease has recently been associated with the presence of these antibodies. The aim of this prospective study was to investigate the levels of APA in subjects affected by haematological malignancies undergoing allogeneic haematopoietic stem cell transplantation (ASCT). Between March 1996 and December 1997, 32 patients undergoing ASCT were studied prospectively until day +180 from transplant. The mean values of IgG and IgM anticardiolipin antibodies (ACA) increased in recipients of stem cells from anunrelated donor, and a statistically significant difference inACA IgG mean value between unrelated and related transplanted patients was demonstrated between days +95 and +180. All of the subjects who received stem cells from an unrelated donor had APA levels higher than the mean normal value +3 SD vs. 35% of those receiving stem cells from a related donor (P < 0.01). The reason for such a difference may be a result of the different incidence in documented cytomegalovirus (CMV) infection in the two groups (83% vs. 23%; P < 0.01), as indicated by the significant correlation between APA positivity and CMV infection (P < 0.05). No relationship was found between APA, conditioning regimen and acute or chronic graft vs. host disease (GVHD). Moreover, we did not observe any thromboembolic disorder or veno occlusive disease (VOD).