Extra-criteria antiphospholipid antibodies in patients with small vessel brain lesions and clinical manifestations associated with antiphospholipid syndrome

ObjectivesNeurological manifestations compatible with small vessel brain lesions (SVBL), such as migraine, cognitive impairment, seizures, and transverse myelitis, may be related to antiphospholipid syndrome (APS) and patients could need APS therapies even though they do not fit into thrombosis or obstetric morbidity. Furthermore, extra-criteria antiphospholipid antibodies (aPL) provide an increase in sensitivity in patients with clinical manifestations related to APS but negative for IgG/IgM anticardiolipin (aCL), anti-β2 glycoprotein I (aβ2GPI), and lupus anticoagulant, which are the antibodies included in the classification criteria for APS.MethodsWe determined extra-criteria aPL in 65 SVBL patients with neurological traits and Magnetic Resonance Imaging suggestive of APS but negative for APS classification criteria, 47 of whom were prospectively followed and tested over three years. A group of 95 patients with autoimmune diseases (AD) but without clinical traits of APS was also studied.ResultsA persistent presence of extra-criteria aPL was detected in 27.7% of patients: 12.77% IgM anti- prothrombin (PT), 6.38% IgG anti-PT, 6.38% IgM anti-phosphatidylethanolamine (PE), 4.26% IgA aβ2GPI, 2.13% IgG anti-phosphatidylserine/prothrombin (PS/PT) and 2.13% IgM anti-PS/PT.There was a tendency towards a higher prevalence of these aPL in SVBL patients than in AD – especially for IgA aβ2GPI – and a lack of IgG aPS/PT positivity in the AD group. We found no SVBL patient positive for IgA aCL, IgG anti-PE, annexin V, or aβ2GPI domain I.ConclusionsExtra-criteria aPL can improve sensitivity for APS diagnosis in patients with SVBL, especially IgA aβ2GPI and IgG anti-PS/PT antibodies.     

Prevalence and significance of anti-prothrombin (aPT) antibodies in patients with Lupus Anticoagulant (LA)

Objective

Anti-prothrombin (aPT) antibodies have been found in Lupus Anticoagulant (LA) positive patients. Their prevalence and relative contribution to thromboembolic risk in LA-positive patients is not well defined. The aim of this study was to determine their presence and association with thromboembolic events in a large series of patients with confirmed LA.

Methods

Plasma from LA-positive patients was collected at Thrombosis Centers and sent to a reference central laboratory for confirmation. Positive plasma was tested using home-made ELISA for the presence of aPT and anti-β₂GPI antibodies.

Results

LA was confirmed in 231 patients. Sixty-one of 231 (26%, 95%CI 22-33) LA positive subjects were positive for IgG aPT and 62 (27%, 95% CI 21-33) were positive for IgM aPT antibodies. Clinical features of Antiphospholipid Syndrome (APS) were not associated with the presence of IgG aPT [43 APS in 61 (70%) positive and 109 APS in 170 (64%) negative IgG aPT subjects, p = ns] or IgM aPT. Rate of positivity of IgG and IgM aβ₂GPI was significantly higher than that of IgG and IgM aPT. Clinical events accounting for APS occurred in 97 of 130 (75%) IgG aβ₂GPI positive and in 55 of 101 (54%) IgG aβ₂GPI negative patients (OR 2.4, 95% CI 1.4 to 4.3, p = 0.002). No significant association with clinical events in patients positive for both IgG aPT and IgG aβ₂GPI as compared to those positive for one or another test was found. When patients negative for both IgG aPT and IgG aβ₂GPI (LA positive only) were compared with remaining patients, a significantly lower association with clinical events was found (OR = 0.4, 95% CI: 0.2 to 0.7, p = 0.004).

Conclusions

As compared to IgG aβ₂GPI, the prevalence of IgG aPT in patients with LA is significantly lower and not associated with the clinical features of APS.     

Antibodies to Domain I of β(2)Glycoprotein I are in close relation to patients risk categories in Antiphospholipid Syndrome (APS)

Introduction

Antiphospholipid Syndrome (APS) is characterized by the presence of circulating antiphospholipid antibodies in patients with thrombosis or pregnancy morbidity. Antibodies involved in these disorders are mainly those directed against β₂-Glycoprotein I (β₂GPI) with the major epitope apparently located on discontinuous antigen with several parts of Domain I (DmI) involved. The relation between anti-DmI antibodies and patients’ risk categories is unknown.

Materials and Methods

The synthetic full-length and correctly-folded DmI (1–64) to set up a competitive inhibition enzyme-linked immunoadsorbent assays (ELISA) was used. Plasma of 22 patients with APS and triple positivity [Lupus Anticoagulant positive (LAC+), IgG anti-cardiolipin positive (aCL+), IgG anti-β₂GPI positive (a β₂GPI +)], 15 with double positivity (IgG aCL+, IgG aβ₂GPI+), 9 with single positivity (IgG aβ₂GPI+) and 20 controls were evaluated.

Results

Median of percentage inhibition was 25.5% [interquartile range (IQR)17.2-33.0] in triple positive patients. Significantly lower inhibition was observed in patients with double positivity, median inhibition 5.0% (IQR 0.0-27.0) and in patients with single positivity median inhibition was 2.0% (IQR 0.5-8.0) (p < 0.0001). No inhibition was detected in control subjects or using β₂GPI peptides (40–52 and 57–70), or when antithrombin, an insignificant control protein was used.

Conclusions

High risk patients with APS and triple laboratory positivity as compared with double and single positivity patients have significantly higher titre of anti-DmI antibodies as evaluated by an inhibition test.     

Does the anti-beta2-glycoprotein I antibody provide additional information in patients with thrombosis?

OBJECTIVE: To investigate whether the anti-beta(2)-glycoprotein I (anti-beta(2)GPI) antibody may provide additional information in patients with thrombosis in conjunction with the lupus anticoagulant (LAC) or anticardiolipin (aCL) antibody. METHODS: We selected 235 patients whose plasma were tested for the presence of all three antiphospholipid (aPL) antibodies (LAC, aCL, and anti-beta(2)GPI) and were positive for at least one aPL antibody from January 2000 to December 2001. The LAC test was performed using dilute activated thromboplastin time reagent (dAPTT) and dilute Russell viper venom time reagent (dRVVT). ACL (IgG/IgM) and anti-beta(2)GPI (IgG/IgM) were detected by enzyme-linked immunosorbent assay (ELISA). Clinical data were collected and analysed in all patients with aPL antibody. RESULTS: Of the 235 patients with aPL, thrombosis was detected in 76 patients (28.0%). Of the 76 patients with thrombosis, 29 were positive for LAC, 9 for aCL, 7 for anti-beta(2)GPI, 3 for LAC+aCL, 9 for aCL+anti-beta(2)GPI, 11 for LAC+anti-beta(2)GPI, and 8 for LAC+aCL+anti-beta(2)GPI. The rate of thrombosis was significantly different (p=0.01) among single positive patients (45/163, 27.6%), double positive patients (23/60, 38.3%), and triple positive patients (8/12, 66.7%). In single positive patients, the rate of thrombosis was highest in LAC positive patients (29/85, 34.1%). In double positive patients, the LAC+anti-beta(2)GPI positive group (11/24, 45.8%) and aCL+anti-beta(2)GPI positive group (9/22, 40.9%) had higher rates of thrombosis than the LAC+aCL positive group (3/14, 21.4%). CONCLUSION: Single positivity for anti-beta(2)GPI explained 9.2% of thrombotic events in the absence of LAC or aCL. Double or triple positivity for aPLs were associated with a higher rate of thrombosis than single positivity for aPL. Our results suggest that anti-beta(2)GPI provides additional information in patients with thrombosis in conjunction with LAC or aCL.     

Antibodies to oxidized LDL/beta2-glycoprotein I in antiphospholipid syndrome patients with venous and arterial thromboembolism

It has been reported that IgG to oxidized LDL/beta2-glycoprotein I (oxLDL/beta2GPI) complexes are associated with arterial thromboembolism (TE) in patients with antiphospholipid syndrome (APS). How these antibodies behave in arterial as compared to venous TE in APS is unknown. The aim of the present study was to evaluate the association of IgG anti-oxLDL/beta2GPI with clinical manifestations in category I APS patients. Fifty-seven APS patients with triple positivity (Lupus Anticoagulant (LAC), anti cardiolipin (aCL) and anti-beta2-glycoprotein I (abeta2GPI) antibodies), 28 with arterial and 29 with venous thromboembolism, were included in the study. There were no differences in the dRVVT ratio, IgG/IgM aCL and IgG/IgM abeta2GPI titers in the two patient groups. There were no differences in the IgG (78.5 U+/-59.8 vs. 112.2 U+/-92.3) and IgM (16.3 U+/-15.9 vs. 21.1 U+/-14.3) anti-oxLDL/beta2GPI mean values. A significant correlation was found between IgG anti-oxLDL/beta2GPI and IgG anti-beta2GPI titers in the whole group of APS patients. Patients in the arterial group were older and had more risk factors for atherosclerosis. Data from this study do not support the hypothesis that IgG anti-oxLDL/beta2GPI are specifically associated to arterial TE in Category I APS patients.     

Antiprothrombin antibodies--are they worth assaying?

According to the preliminary classification criteria of the antiphospholipid syndrome (APS) (Sapporo Criteria), β2-glycoprotein I (β2GPI)-dependent anticardiolipin antibodies (aCL) and lupus anticoagulant (LA) are the only laboratory tests considered as criteria for the classification of the APS. Recently, antibodies against phosphatidylserine–prothrombin complex (aPS/PT) have been detected and these antibodies, rather than antibodies against prothrombin alone, are closely associated with APS and LA. We assessed the sensitivity and specificity of aPS/PT for the diagnosis of APS in our population of patients with a variety of autoimmune disorders and investigated whether aPS/PT could be used as diagnostic test in patients suspected of having APS. The study population comprised 219 patients with autoimmune diseases including 82 patients with APS and 137 without APS (55 systemic lupus erythematosus, 32 rheumatoid arthritis, 10 primary Sjogren's syndrome, 8 scleroderma, 5 Behcet's disease and 27 other rheumatic diseases). IgG/M aPS/PT were measured by ELISA using phosphatidylserine–prothrombin complex as antigen immobilized on ELISA plates in the presence of CaCl₂. IgG/M aCL were measured by standard methods and LA was detected by clotting assays. aPS/PT, aCL and LA were more frequently found in patients with APS (47, 46 and 69, respectively) than in those without APS (11, 19 and 29, respectively) (OR 95% [CI]; 15.4 [7.2–32.7], 7.9 [4.1–15.2, 19.8 [9.6–40.6], respectively]. The sensitivity of each assay for the diagnosis of APS was 57%, 56% and 86% with a specificity of 92%, 86% and 79%, respectively. aPS/PT and aCL have similar diagnostic value for APS, therefore, we propose that aPS/PT should be further explored, not only for research purposes, but also as a candidate of one of the laboratory criteria for the classification of the APS.     

An adapted ELISA method for differentiating pathogenic from nonpathogenic aPL by a beta 2 glycoprotein I dependency anticardiolipin assay

With the currently available commercial kits, as well as homemade assays for detecting anticardiolipin antibodies (aCL), it is not possible to discriminate nonpathogenic, beta 2 glycoprotein (GPI)-independent, infection-related antibodies from those of patients with the true autoimmune thrombotic syndrome, known as antiphospholipid syndrome (APS). We devised an assay that is able to differentiate these two types of antibodies by determining the beta 2 GPI requirements to bind in a cardiolipin ELISA. Beta 2 GPI was purified by perchloric acid precipitation, and fixed amounts were used in the dilution solutions of the tested samples that were also tested with no source of beta 2 GPI. The ELISA plates were coated with cardiolipin, as usual, and blocked with a chicken ovalbumin solution. The serum samples had to be highly diluted in order not to have beta 2 GPI from the patient serum. The reaction was detected with alkaline phosphate tablets and developed with pNp in diethanolamine buffer. The adapted ELISA aCL assay described here was able to discriminate infectious [syphilis, hepatitis C virus (HCV), dengue fever, human immunodeficiency virus (HIV) and leprosy] and autoimmune [primary APS and systemic lupus erythematosus (SLE) related APS]. Further testing should be performed to demonstrate that this method consistently differentiates pathogenic antibodies that bind in an aCL ELISA only in the presence of beta 2 GPI.     

Higher serum clozapine level is associated with increased antiphospholipid antibodies in schizophrenia patients

Objectives

This study was to evaluate the relationship between clozapine and aPL in schizophrenia patients.

Methods

163 Participants were evaluated: 37 unmedicated schizophrenia patients, 50 clozapine-treated schizophrenia patients and 76 age- and sex-matched healthy controls. A fasting blood sample was taken for serum aPL and serum clozapine level. Serum aPL were measured by ELISA technique and HPLC method was used for the determination of serum clozapine level.

Results

The unmedicated schizophrenia patients showed higher IgG aCL level [mean ± SD: 1.51 ± 0.81 and 1.25 ± 0.13 U, respectively (t = 2.77, df=111, p<0.01)] and IgM aCL level [mean±SD: 1.53 ± 0.54. and 1.33 ± 0.15 U, respectively (t = −2.98, df = 111, p < 0.01)] compared with the healthy controls. The comparison of the clozapine-treated schizophrenia patients and the healthy controls showed significant difference in IgG aCL level [mean ± SD: 1.74 ± 0.90 and 1.25 ± 0.13 U, respectively (t = −4.77, df = 124, p < 0.01)] and IgM aCL level [mean ± SD: 1.62 ± 0.83 and1.33 ± 0.15 U, respectively (t = −4.35, df = 124, p < 0.01)]. In clozapine-treated schizophrenia patients, the results of Pearson correlation coefficients showed that there was a significant positive relationship between serum IgM aCL and serum clozapine level (r = 0.461, p < 0.01), and serum IgG aCL were significantly correlated with serum IgM aCL (r = 0.279, p < 0.05). Stepwise multiple regression analysis was performed with various characteristics, such as duration of medication, daily dose and serum clozapine level as candidate factors for serum aCL (IgG and IgM isotypes) in clozapine-treated schizophrenia patients. Only serum clozapine level was able to enter into the regression model of IgM aCL (Model R² = 0.212, p < 0.05).

Conclusions

A higher serum clozapine level is associated with an increased aPL in schizophrenia patients.     

Platelet activation rather than endothelial injury identifies risk of thrombosis in subjects positive for antiphospholipid antibodies

BACKGROUND: Anti-phospholipid antibodies (APLA) are often associated with thrombosis, defining the antiphospholipid syndrome (APS) but it remains unclear why many subjects who are positive for APLA chiefly anti-cardiolipin (aCL) or anti-beta2GPI (abeta2GPI) do not develop thrombosis. A related question addressed in this study is whether the target of cellular injury in APS is predominately platelets or endothelial cells (EC). METHODS: aCL and abeta2GPI were determined by ELISA in 88 patients, 60 of whom were thrombotic and 28 non-thrombotic. Platelet activation was measured by CD62P and by concentration of platelet microparticles (PMP) and EC activation was assessed by endothelial microparticles (EMP), both by flow cytometry. Lupus anticoagulant (LAC) was measured in the hospital laboratory. RESULTS: There was no difference in frequency of aCL or abeta2GPI, neither IgG or IgM, between the thrombotic and non-thrombotic groups. Both groups showed elevated EMP compared to controls but this did not differ between thrombotic and non-thrombotic groups. In contrast, PMP were not significantly elevated in non-thrombotic but were elevated in thrombotic compared to non-thrombotic (p=0.03) and controls. CD62P, an independent marker of platelet activation, was also elevated in thrombotic vs. non-thrombotic. There was a trend for increased LAC in the thrombotic group but not significant. CONCLUSION: Although all subjects had evidence of endothelial activation, only platelet activation differed between thrombotic and non-thrombotic. This supports the hypothesis that platelet activation predisposes to thrombosis in the presence of chronic EC activation. These data also raise the possibility of distinguishing risk-prone APLA-positive individuals.     

Detection of complement-fixing antiphospholipid antibodies in association with thrombosis

Antiphospholipid antibody (aPL) is a hallmark of antiphospholipid syndrome (APS), characterized by thrombosis and recurrent fetal loss. We developed a novel ELISA system to detect complement-fixing ability of anticardiolipin antibody (aCL), and evaluated its clinical usefulness through studying the prevalence of the antibodies in rheumatic diseases, especially in association with thrombosis and recurrent abortion. Among 189 patients with rheumatic diseases, the complement-fixing aCL was positive in 26 (83.9%) of 31 patients with APS and 2 (1.3%) of 158 with other disease categories, whereas it was not positive among 52 normal subjects. Twenty-seven of 28 patients (96.4%), who were positive for complement-fixing aCL, had the episodes or history of thrombosis and/or recurrent abortion, at the time we studied. The remaining one in this group developed APS manifesting pulmonary infarction and occlusion of mesenteric artery 6 months after the evaluation. The sensitivity and specificity of this assay system were 75.0% and 99.3%, respectively, in relation with thrombotic episodes. On the other hand, the IgG aCL were positive in 28 (77.8%) of 36 cases with recent thrombotic episodes and 24 (15.7%) of 153 cases with no recent thrombotic episodes. The sensitivity and specificity of IgG aCL assay system were 77.8% and 84.3%, respectively, in relation with thrombotic episodes. These results indicate that complement-fixing aCL may specifically occur in association with the episodes of thrombosis and/or recurrent abortion in patients with APS compared to IgG-aCL. The method for detecting the complement-fixing aCL is simple, and it provides the useful diagnostic marker for thrombotic manifestations associated with APS.     

Thromboembolic risk in patients with high titre anticardiolipin and multiple antiphospholipid antibodies

Asymptomatic antiphospholipid antibody (aPL) carriers with high risk for thrombosis may benefit from preventive anticoagulation. It was our objective to test whether the risk of thrombosis increases with: 1). increasing titres of anticardiolipin antibodies (aCL) after adjustment for other cardiovascular risk factors and 2). the number of aPL detected. In a cross-sectional study, blood was collected from clinics in two teaching hospitals. The study included 208 individuals suspected of having an aPL and 208 age- and sex-matched controls having blood drawn for a complete blood count. Clinical variables included history of previous arterial (ATE) or venous (VTE) thrombotic events, traditional risk factors for cardiovascular disease, and systemic lupus erythematosus (SLE). Laboratory variables included IgG/IgM aCL, lupus anticoagulant, and IgG/IgM anti-beta2-glycoprotein I. Mean age was 46.5 years and 83% were female. Seventy-five of the 416 participants had >or= 1 aPL, and 69 had confirmed >or= 1 ATE or VTE. Family history was positive in 48% of participants, smoking in 28%, hypertension in 16%, diabetes in 6%, and SLE in 20%. A 10-unit increase in aCL IgG titre was associated with an odds ratio (OR) [95% CI] of 1.07 [1.01-1.13] for ATE and 1.06 [1.02-1.11] for VTE. The odds of a previous thrombosis increased with each additional aPL detected: 1.5 [0.93-2.3] for ATE and 1.7 [1.1-2.5] for VTE. These results indicate that increased titres of aCL and multiple aPL were associated with an increased risk of a previous thrombotic event.     

Distinguishing features of anti-beta2 glycoprotein I antibodies between patients with leprosy and the antiphospholipid syndrome

Anticardiolipin (ACA), anti-beta2 glycoprotein I (beta2GPI), and antiprothrombin antibodies of IgG and IgM classes were quantitated by enzyme-linked immunosorbent assays in 176 untreated leprosy patients across the histopathological spectrum. Positivity rates ranged from 21% (IgG ACA) to 30% (IgM anti-prothrombin) versus 4% in healthy controls (p <10(-2) to 10(-3)). Levels of IgM anti-beta2GPI and IgG ACA were significantly higher in lepromatous leprosy and multibacillary patient subgroups. IgG3 was the most common subclass reactive to both beta2GPI and prothrombin in selected high-titer leprosy sera, unlike antibodies from patients with the antiphospholipid syndrome (APS) largely restricted to IgG2. In leprosy patients, but not in the APS control group, there was no statistical correlation between ACA and anti-beta2GPI antibody levels. Likewise, a large fraction of anti-beta2GPI positive sera (36/45 and 28/44 for IgG and IgM, respectively) were unreactive in the standard ACA assay. Most assayed anti-beta2GPI antibodies from leprosy patients showed (i) ability to recognize both human and bovine beta2GPI immobilized on non-irradiated polystyrene plates, (ii) concentration-dependent inhibition of binding by cardiolipin, and (iii) relatively high avidity binding to fluid-phase beta2GPI, thereby differing from those found in APS. Finally, the location of the major epitopic region on the beta2GPI molecule targeted by autoantibodies was different in leprosy and APS, as assessed by direct binding to domain I- and V-deleted mutants and competition with the mouse monoclonal antibody 8C3, directed at domain I. Thus, leprosy-related antiphospholipid antibodies comprise persistent IgG and IgM anti-beta2GPI that differ from APS-related ones with respect to IgG subclass, avidity and epitope specificity, possibly reflecting distinct pathophysiological significance.     

A novel ELISA system for simultaneous detection of six subclasses of anti-phospholipid antibodies for prediction of thrombotic complications among SLE patients

Background

Anti-phospholipid antibodies (aPLs) are frequently associated with arterial and/or venous thromboembolic complications and recurrent fetal loss in patients with systemic lupus erythematosus (SLE). We recently reported that the clinical picture of SLE apparently depends on subclasses of aPLs in the patient’s sera, but the contribution of each subclass remains uncertain.

Methods

We newly developed an ELISA system for simultaneous detection of six specific categories of aPLs: anti-cardiolipin (aCL), anti-β₂-glycoprotein I (aβ₂GPI), anti-cardiolipin/β₂-glycoprotein I (aCL/β₂GPI), anti-phosphatidylserine (aPS), anti-prothrombin (aPT), and anti-phosphatidylserine/prothrombin (aPS/PT). They were measured in 331 patients with SLE including 63 patients with arterial thromboembolic complications, 64 with venous thromboembolic complications, and 43 with recurrent fetal loss. Lupus anticoagulant (LA) activity in their plasma was measured according to the guidelines recommended by the Subcommittee on Lupus Anticoagulant/Phospholipid-Dependent Antibodies.

Results

Multivariate logistic analysis revealed that the concentration of aPS/PT was most closely associated with arterial thrombosis. In contrast, the concentration of aβ₂GPI was most closely related to venous thrombosis. Furthermore, both aCL/β₂GPI and aPS/PT were independently associated with episodes of recurrent fetal loss. Regarding the relation between APLs and LA activity, aPS/PT, followed by aβ₂GPI and aPT, showed the closest association with the presence of LA activity.

Conclusions

Anti-phospholipid syndrome in patients with SLE can be classified by antigenic specificities of their aPLs as to their susceptibility to arterial and/or venous thromboembolic complications or obstetric complications.     

Laboratory classification categories and pregnancy outcome in patients with primary antiphospholipid syndrome prescribed antithrombotic therapy

Background

A relationship between antibody profile and pregnancy outcome in patients with a previous diagnosis of primary antiphospholipid syndrome (APS) has not been clearly documented.

Methods

Women attending our Center with primary APS characterized by the presence in the blood of one or more of the following: Lupus Anticoagulant (LA), IgG/IgM anticardiolipin (aCL), IgG/IgM anti-human β2-Glycoprotein I (aβ2GPI) antibodies (confirmed after a minimum of 3 months) were considered eligible for this study. Women who became pregnant during the study period with the exception of those with congenital thrombophilia or other congenital abnormalities were included in our analysis. Primary outcome events, defined as early abortion or fetal death, were evaluated in relation to the laboratory classification category assigned to each patient at the time they were diagnosed with APS.

Results

A total of 97 pregnancies occurring in 79 primary APS patients during the study period were analyzed. Twelve out of 97 pregnancies were unsuccessful, 11 out of 65 (16.9%) in category I patients (more than one positive laboratory test) and 1 out of 32 (3.1%) in category II patients (single positive test; adjusted hazard ratio 1.9; 95% CI, 0.2 to 18.9, p = 0.6). Pregnancy loss took place in 10 out of 19 pregnancies (52.6%) in women belonging to category I with triple positivity and in 1 out of 46 pregnancies (2.2%) in patients with double positivity. The rate of pregnancy loss was more frequent in the 19 pregnancies of patients with triple positivity than in the 46 pregnancies of double positive patients (adjusted hazard ratio 23, 95% CI, 1.3 to 408, p = 0.03).

Conclusion

Poor pregnancy outcomes occur more frequently in category I than in category II primary APS patients. However, it has been seen that a greater predictability is achieved when category I patients are grouped into triple and double positivity states.     

Anticardiolipin antibody assay: a methodological analysis for a better consensus in routine determinations--a cooperative project of the European Antiphospholipid Forum

Despite the widely recognized practical importance of anticardiolipin (aCL) ELISA, the reliability of this test has been recently discussed. In order to investigate this area on European scale, we sent to 30 experienced centers a questionnaire focusing on the diagnostic procedures applied to patients with antiphospholipid syndrome (APS) and on the detailed protocols used to perform aCL. Anticardiolipin ELISA was found to be the most frequently performed test in patients with suspected APS, but significant difference was shown among the various protocols. The cross-laboratory multiple examination of ten serum samples evaluated independently by the 24 centers pointed out the difficulty in getting comparable results. Therefore a "consensus" protocol was derived from the aCL methods giving the best performance. The materials and reagents necessary to perform the "consensus" method, including, as putative standards, one IgG and one IgM monoclonal antibody (HCAL and EY2C9) were distributed to 19 Centers. The results of one IgG and one IgM aCL high positive sera measured in serial dilutions were compared. A progressive decrease in the variability of the values obtained for a given sample appeared evident when all the laboratories used the same standard, in their own in-house ELISA and even more in the "consensus" ELISA. Our data show that aCL ELISA standardization is necessary in order to obtain comparable results in different laboratories.     

Antiphospholipid syndrome: diagnostic aspects of lupus anticoagulants

Antiphospholipid syndrome (APS) is an autoimmune disorder in which antiphospholipid antibodies (aPL) are thought to be involved in the development of venous and/or arterial thrombosis. APL found in this syndrome are antibodies directed against a variety of phospholipid (PL) binding-proteins of which beta3-glycoprotein I (beta2GPI) and prothrombin are considered to be the major antigens. Some of these antibodies prolong PL-dependent clotting reactions and are termed lupus anticoagulants (LA). Autoimmune aPL which bind through beta2GPI to cardiolipin are called anticardiolipin antibodies (aCL). Clinical studies indicate that LA is a stronger risk factor for thrombosis than aCL. The production of monoclonal antibodies against beta2GPI and prothrombin has enabled us to understand the mechanism by which LA prolong coagulation in vitro. LA form bivalent antigen-antibody complexes with increased affinity for PL which compete with coagulation factors for the same catalytic surface. These LA positive monoclonal antibodies may be helpful in further improving the laboratory diagnosis of LA.     

Functional analyses of patient-derived IgG monoclonal anticardiolipin antibodies using in vivo thrombosis and in vivo microcirculation models

Antiphospholipid antibodies (aPL) have been associated with thrombosis and pregnancy losses in patients diagnosed with antiphospholipid syndrome (APS) and enhance thrombus formation in vivo in mice, but the mechanism of thrombosis by aPL is not completely understood. It has been proposed that aPL may affect endothelial cell (EC) function and/or induce their activation, transforming their anticoagulant surface into procoagulant, thus predisposing to thrombosis. It has been proposed that aPL may affect EC cell function and/or induce their activation, transforming their anticoagulant surface into procoagulant, thus predisposing to thrombosis. This study proposes to test the hypotheses that some IgG anticardiolipins (IgG aCL) with thrombogenic properties in mice, exert their effects through activation of endothelium. We studied seven patient-derived monoclonal aCL for their thrombogenic properties in an in vivo pinch-induced thrombosis model, and their functional activities in activating EC by analyzing in vivo leukocyte adhesion to endothelium in microcirculation in venules in exposed murine cremaster muscle and in vitro adhesion molecule expression in cultured EC. The binding of the monoclonal aCL to EC was also tested. In addition to the previous identified thrombogenic IS2, four of the five new more IgG monoclonal aCL (from two patients) were found to be thrombogenic. Of these five thrombogenic aCL, three caused more in vivo leukocyte adhesion to EC in microcirculation, as compared to that induced by the H2 control human monoclonal IgG, and enhanced expression of adhesion molecules (particularly VCAM-1) on cultured EC. These data show that about 2/3 patient-derived IgG monoclonal aCL are thrombogenic and suggest that some thrombogenic IgG aCL exert their effects through activating EC.     

Antibody profile and clinical course in primary antiphospholipid syndrome with pregnancy morbidity

In women diagnosed as having category I primary obstetric antiphospholipid syndrome, clinical characteristics and the risk of subsequent thromboembolic events and further unsuccessful pregnancy has not been clearly documented. Women with unexplained obstetric complications and no definite autoimmune systemic diseases were tested for lupus anticoagulant (LA), IgG/IgM anticardiolipin (aCL) and IgG/IgM anti-human beta2-Glycoprotein I (abeta2GPI) antibodies and diagnosed as having primary antiphospholipid syndrome (APS) in classification category I on the basis of more than one laboratory criteria present in any combination. Characteristics at the time of diagnosis and risk factors for subsequent clinical events during a mean follow-up of 6.3 years were evaluated. Fifty-three of 600 women studied were found to fulfil obstetric criteria and had more than one positive laboratory test at the time of diagnosis. All the women were aCL and abeta2GPI positive, and 16 were also LA positive. This latter group (triple positivity) had distinct features and had more frequently experienced previous thromboembolism (OR = 122.5, 95% CI 16-957, p < 0.001). They also had an increased rate of late pregnancy loss (OR = 16.2, 95%CI 0.9-292, p = 0.01), and a higher IgG abeta2GPI titer at diagnosis (median, 25(th) and 75(th) percentile were 118, 37-962, vs. 23, 18-32, respectively, p < 0.0001). During follow-up, the rate of thromboembolic events was significantly higher in the group of women with triple positivity and/ or previous thromboembolism (OR = 57.5, 95% CI 2.7-1160, p = 0.0004) which were the only independent predictors of TE in the multivariate model. Recurrent pregnancy loss took place in seven out of 47 women who had a new pregnancy. Triple positivity and/or previous thromboembolism were again the only independent markers (OR = 34.4, 95% CI 3.5-335.1, p = 0.003) of an unsuccessful new pregnancy. In conclusion, in primary APS with pregnancy morbidity in classification category I, quite different groups of patients may be identified on the basis of laboratory tests. Triple positivity and/or a history of thromboembolism predict new TE events and new unsuccessful pregnancies.     

A cross sectional study of antiphospholipid-protein antibodies in patients with venous thromboembolism

OBJECTIVE: To look for an association between venous thromboembolism (VTE) and antiphospholipid antibodies (aPL) in patients without Systemic Lupus Erythematosus (SLE) when implementing, beside conventional assays, new tests for aPL screening directed towards purified proteic targets. METHODS: We conducted a cross-sectional, hospital-based study of consecutive unselected outpatients. We compared VTE+ patients to VTE- among 398 consecutive unselected outpatients referred for clinical suspicion of VTE. To detect aPL, the following ELISAs were performed: 1) a conventional standardized ELISA 2) an improved APA assay, 3) an anti-Beta2GPI ELISA, 4) an anti-Annexin V ELISA, 5) an anti-Prothrombin ELISA. We sought an association between VTE and aPL through a quantitative (t-test) and a qualitative comparison (chi-square test, according to the cut-off values set as the 95th percentile of aPL distribution). First we conducted an analysis of all patients. Then we stratified them into 2 subgroups, with or without a wellknown risk factor for VTE (prolonged immobilization >72h, surgery or trauma within the past three months, current malignancy). RESULTS: 61% of patients were classified as VTE-positive. Before stratification, we did not find any significant association between the VTE status and aPL. However, after stratification, in the subgroup without risk factors for VTE, the frequency of positive values as regards the anti Prothrombin antibodies detection was significantly higher in VTE+ patients (p = 0,04). CONCLUSION: The presence of anti Prothrombin antibodies might be an independent risk factor of VTE. However systematic screening for aPL in non SLE patients referred for VTE suspicion at the time of the thrombo-embolic event has little clinical relevance.     

Elevated anticardiolipin antibodies in schizophrenic patients before and during neuroleptic medication

The objective of this study was to examine the prevalence of IgG and IgM anticardiolipin antibodies (aCL) in schizophrenic patients and to determine the relation of aCL levels with neuroleptic medication and psychotic symptoms. Twenty-three patients with acute episodes of chronic schizophrenia, drug-free for at least 3 months before entering the study, were tested for aCL at admission (T1) and 42 days (T2) after neuroleptic treatment started. Blood samples were taken from 20 healthy volunteers as well. Diagnosis was performed according to DSM-IV. Serum samples were analysed for IgG and IgM autoantibodies against beta2-glycoprotein-1-cardiolipin complex by commercially available ELISA kits (Binding-site, UK). Significantly higher levels of aCL antibodies of both isotypes were found in schizophrenic patients versus controls. In patients IgM-aCL positivity was significantly more frequent than in controls. The elevated IgM-aCL and IgG-aCL values were not associated with neuroleptic treatment and psychotic symptoms, as measured by the Positive and Negative Syndrome Scale and the Pentagonal Structural Model of Schizophrenic Symptoms. The negative correlation of IgM-aCL and IgG-aCL with the positive symptoms scale and the autistic preoccupation scale (Pentagonal Structural Model) may indicate the consumption of these antibodies in the exacerbation of the disease.