Antibodies to phosphatidylserine/prothrombin complex as an additional diagnostic marker of APS?

Antiprothrombin antibodies can be measured by ELISA using either a prothrombin/phosphatidylserine complex (aPS/PT) or prothrombin alone (aPT) as antigen. We aimed to compare the clinical features of autoimmune patients with avidity of aPS/PT and determine the diagnostic efficiency of aPS/PT and aPT for assessing antiphospholipid syndrome (APS). aPS/PT were of low (n = 9), heterogeneous (n = 31) and high (n = 8) avidity out of 48 cases. None of the samples with low avidity were positive in aPT ELISA. Among patients with heterogeneous or high avidity aPS/PT, there was a significantly greater number of patients with APS as compared to patients with low avidity (38/39 vs. 7/9; p < 0.05). No SLE patients had high avidity antiprothrombin antibodies.

Avidity of anti-ß2-glycoprotein I antibodies in patients with antiphospholipid syndrome.

Antibodies against ß(2)-glycoprotein I (anti-ß(2)GPI) are one of the hallmarks of the antiphospholipid syndrome (APS). However, they are heterogenic regarding their epitope specificity, pathogenic mechanisms and their avidity. In the current study we present some outstanding issues about avidity of anti-ß(2)GPI antibodies. Our results confirmed that high avidity anti-ß(2)GPI are associated with thrombosis and APS, while in low avidity anti-ß(2)GPI group non-APS (predominantly systemic lupus erythematosus) patients prevailed.

Autoimmune response following influenza vaccination in patients with autoimmune inflammatory rheumatic disease.

Vaccines have undoubtedly brought overwhelming benefits to mankind and are considered safe and effective. Nevertheless, they can occasionally stimulate autoantibody production or even a recently defined syndrome known as autoimmune/inflammatory syndrome induced by adjuvants (ASIA). There is scarce data regarding autoimmune response after seasonal/influenza A (H1N1) vaccine in patients with autoimmune inflammatory rheumatic disease (AIRD). The objective of our study was therefore to determine autoimmune response in a large group of AIRD patients vaccinated against seasonal and/or H1N1 influenza. We conducted a prospective cohort study with a 6-month follow-up. Two-hundred and eighteen patients with AIRD (50 vaccinated against seasonal influenza, six against H1N1, 104 against both, 58 non-vaccinated controls) and 41 apparently healthy controls (nine vaccinated against seasonal influenza, three against H1N1, 18 against both, 11 non-vaccinated controls) were included. Blood samples were taken and screened for autoantibodies [antinuclear antibody (ANA), anti-extractable nuclear antigen (anti-ENA), anticardiolipin (aCL) IgG/IgM antibodies, anti-beta 2-glycoprotein I (anti-ß2GPI)] at inclusion in the study, before each vaccination, 1 month after the last vaccination and 6 months after inclusion. For non-vaccinated participants (patients and healthy controls) blood samples were taken at the time of inclusion in the study and 6 months later. We report that after the administration of seasonal/H1N1 vaccine there were mostly transient changes in autoantibody production in AIRD patients and in healthy participants. However, a small subset of patients, especially ANA-positive patients, had a tendency towards anti-ENA development. Although no convincing differences between the seasonal and H1N1 vaccines were observed, our results imply that there might be a slight tendency of the H1N1 vaccine towards aCL induction. Although seasonal and H1N1 vaccines are safe and effective, they also have the potential to induce autoantibodies in selected AIRD patients and healthy adults. Follow-up of such individuals is proposed and further research is needed.

Safety and efficacy of influenza vaccination in a prospective longitudinal study of 31 children with juvenile idiopathic arthritis.

OBJECTIVES: Influenza vaccination in children with rheumatic diseases is often recommended, but not frequently performed. Our aim was to assess the safety and efficacy of annual influenza vaccination in a longitudinal follow-up study of an unselected group of children with juvenile idiopathic arthritis (JIA). METHODS: Thirty-one children with stable JIA (10 boys, 21 girls, mean age 11.0 years) receiving various therapies and 14 children in a control group (10 boys, 4 girls, mean age 11.9 years) were vaccinated with the annual influenza vaccine Begrivac® 2008/2009. The children in both groups were followed for adverse events and infections 6 months after vaccination. Autoantibodies production and antibody titers against three vaccine viruses were determined in serial samples taken before, 1 and 6 months after vaccination. RESULTS: Eleven (35%) children with JIA and 5 (36%) children in the control group reported short-term adverse events. A JIA flare was observed one month after vaccination in 4 (13%) patients, and in the following five months in 7 (23%) patients. The response to vaccination after one month was significant in the control and study groups as a whole, but not in a subgroup of 4 children receiving anti-TNF-α therapy. After six months, no significant differences in the protective titers against vaccine viruses among the patient and control groups were observed. Changes in the mean values of autoantibodies after vaccination were found only for IgG aCL in the JIA group. CONCLUSIONS: No long-term adverse events were reported after influenza vaccination in JIA and control group. Thirty-five percent of children with JIA experienced flare of the disease after vaccination. Protective antibodies against at least 2 vaccine viruses 6 months after vaccination were detected in all patients.

The avidity of anti-beta2-glycoprotein I antibodies in patients with or without antiphospholipid syndrome: a collaborative study in the frame of the European forum on antiphospholipid antibodies.

OBJECTIVE: The objective of this study was to extend the findings of the preliminary study by measuring the avidity of IgG anti-ß2-glycoprotein I antibodies (anti-ß2-GPI) on a larger group of patients with primary or secondary antiphospholipid syndrome (APS) and anti-ß2-GPI positive patients without APS in the frame of the European Forum on antiphospholipid antibodies (aPL). METHODS: Serum from 137 patients with primary APS, APS associated with autoimmune diseases, and patients with autoimmune diseases other than APS from five EU rheumatology centres were tested for anti-ß2-GPI antibodies. The 109 patients who were sera positive for anti-ß2-GPI by the in-house anti-ß2-GPI enzyme-linked immunosorbent assay (ELISA) at the Immunology Laboratory, UMC Ljubljana were selected for further testing on avidity with chaotropic anti-ß2-GPI ELISA. RESULTS: High, low and heterogeneous avidity IgG anti-ß2-GPI was found in 32/109, 17/109 and 60/109 patients respectively. Significantly more patients with APS were in the high avidity than in the low avidity anti-ß2-GPI group, while the opposite was observed for non-APS (both p < 0.001). The most common clinical feature among patients with high avidity anti-ß2-GPI was thrombosis, mainly due to venous thrombosis (p < 0.01 and p < 0.001, versus low avidity anti-ß2-GPI group). CONCLUSION: Patients with or without APS had anti-ß2-GPI of high, low or heterogeneous avidity. High avidity anti-ß2-GPI was associated with thrombosis and APS, while in the low avidity anti-ß2-GPI group non-APS (predominantly SLE) patients prevailed. Determination of anti-ß2-GPI avidity should be considered in the analytical strategies for further differentiation of patients with anti-ß2-GPI antibodies.

Autoantibodies against dsDNA measured with nonradioactive Farr assay-an alternative for routine laboratories.

Autoantibodies against dsDNA are utilized for the diagnosis and prognosis of SLE as they are highly specific and correlate with disease activity/renal involvement. However, different detection methods are used in routine diagnostic laboratories. Farr radioimmunoassay (Farr-RIA) has been designated as the preferred method, since it provides very specific and at the same time quantitative results, enabling follow-up of level variations over time. Using intercalating fluorescent dsDNA dye would enable all the benefits of Farr-RIA without the radioactive material and organic solvents. To develop a modified fluorescent Farr method (Farr-FIA) and compare it to the classical Farr-RIA in regard to laboratory parameters, as well as clinical utility. Assays were tested on sera of 70 SLE patients, 78 other autoimmune patients, and 145 healthy blood donors. DNA for Farr-FIA was isolated from healthy donor, for Farr-RIA, 14C-labeled dsDNA from E. coli was used and mixed with sera in borate-buffered saline, followed by precipitation with saturated ammonium sulfate solution and centrifugation. The supernatant (S) was separated from the precipitate (P), and content of dsDNA was measured with PicoGreen (Invitrogen) in Farr-FIA or radioactive isotope in scintillation solution in Farr-RIA. The results were calculated as a ratio (P-S)/(P+S). Farr-FIA has a diagnostic sensitivity of 53% and diagnostic specificity of 100% (ROC AUC 0.781). Good correlation and agreement were shown between Farr-RIA and Farr-FIA. Also, there is good correlation between Farr-FIA and SLEDAI, comparable to that of Farr-RIA. Farr-FIA differs from Farr-RIA in the changed detection system yielding comparable results and thus could represent a nonradioactive replacement for Farr-RIA.

Autoimmune and proinflammatory activity of oxidized immunoglobulins.

AIMS: Oxidation reactions can modify protein activity or specificity. Recently, a novel redox-reactive family of autoantibodies was described, which indicated involvement of altered antibodies (beside altered antigens) into autoimmune reactions. The aim of our study was to determine the binding capacity alterations of electro-oxidized blood donors' IgGs, and to evaluate their effects on released proinflammatory interleukin 6 in HUVEC. RESULTS: We found out that 1.) Isolated blood donor IgGs bound after electro-oxidation to beta2-glycoprotein I, cardiolipin, citrullinated cyclic peptide and protein 3 by enzyme-linked immunosorbent assay, extractable nuclear antigens by counterimmuno-electrophoresis, and cell antigens by indirect immunofluorescence; 2.) Alterations in immunoreactivity of IgGs due to oxidation highly depend on electric current, time of exposure and the presence of antioxidants, 3.) Treatment of HUVEC with oxidized IgGs resulted in changed cell morphology, accompanied by an increase in released interleukin-6. CONCLUSIONS: Our data suggest repeatable transformation of antibodies present in the blood of healthy persons and patients. Inter-individual differences in chemical stability of antibodies, patient's antioxidant status, and the microenvironmental changes at the cellular level may influence the range of antibody alterations and their involvement in pathophysiological autoimmune processes.

Prevalence and clinical associations of anti-Ku antibodies in patients with systemic sclerosis: a European EUSTAR-initiated multi-centre case-control study.

OBJECTIVES: To determine the prevalence of anti-Ku antibodies in 625 patients with systemic sclerosis (SSc) from six European rheumatological centres and to evaluate their clinical and serological characteristics. METHODS: Sera of 625 consecutive patients with either limited cutaneous or diffuse cutaneous SSc were tested for antibodies to Ku antigen together with other extractable nuclear antigens by counterimmunoelectrophoresis. A case-control design with calculation of bootstrap 95% confidence intervals derived from anti-Ku negative control patients was used to evaluate clinical associations of anti-Ku antibodies. Sera from anti-Ku positive patients with SSc and a control group were additionally tested by immunofluorescence on Hep-2 cell substrates and line immunoassay. RESULTS: Anti-Ku antibodies were found in the sera of 14/625 (2.2%) patients with SSc. Of 14 anti-Ku positive patients with SSc, 10 had no other anti-extractable nuclear antigen (ENA) antibodies detected by counterimmunoelectrophoresis. Using a case-control study design, anti-Ku antibodies were significantly associated with musculoskeletal manifestations such as clinical markers of myositis, arthritis and joint contractures. In addition, a significant negative correlation of anti-Ku antibodies was found with vascular manifestation such as fingertip ulcers and teleangiectasias. There was a striking absence of anti-centromere antibodies as well as anti- polymyositis (PM)/scleroderma (Scl) antibodies in patients that were anti-Ku positive. As expected, anti-Scl70 and punctate nucleolar immunofluorescence patterns were present only in single cases. CONCLUSION: This is the largest cohort to date focusing on the prevalence of anti-Ku antibodies in patients with SSc. The case-control approach was able to demonstrate a clinically distinct subset of anti-Ku positive patients with SSc with only relative clinical differences in skeletal features. However, the notable exceptions were signs of myositis. This shows the importance of anti-Ku antibody detection for the prediction of this specific clinical subset.

Changes in avidity and specificity of IgG during electro-oxidation. Relevance of binding of antibodies to beta2-GPI.

The immune response may be changed due to altered proteins or modifications of immunoglobulins, including oxidative processes. The susceptibility to oxidative modifications depends greatly on amino-acid moiety composition due to chemical characteristics (instability) of their side-chains. Initial steps of oxidation may change the specificity and avidity of immunoglobulins due to chemical alteration of the hypervariable region. The oxidation of antibodies increases the hydrophilic nature of the paratopes and makes them more susceptible for the binding to cationic surfaces even without the strong surface-to-surface fitting. The electro-oxidation of IgG significantly changes the immunoreactivity and specificity of IgG fractions, regardless of the initial immunoreactivity to a specific autoantigen also in healthy persons. Data are presented on changes in the immunoreactivity as well as the avidity of antibodies against beta2-glycoprotein I after being exposed to direct current. ELISA measurements showed increased reactivity of anti-beta2-glycoprotein I antibodies at the beginning and various, fluctuating results after prolonged exposure to electro-oxidation. Inter-individual differences in chemical stability of immunoglobulins and patient's antioxidative status may influence the range of their alterations and their impact on health/disease balance.

Serum amyloid A in autoimmune thrombosis.

The objectives of this study were (1) to determine how levels of serum amyloid A (SAA), high sensitivity C-reactive protein (CRP) and interleukin-6 (IL-6) correlate to autoimmune diseases in patients with or without thrombosis, and (2) to discuss the parameters that influence the relative SAA values. SAA, CRP and IL-6 concentrations were determined by enzyme linked immunosorbent assay (ELISA). 84 patients with secondary antiphospholipid syndrome (SAPS), primary antiphospholipid syndrome (PAPS), systemic lupus erythematosus with antiphospholipid antibodies (SLE+aPL), SLE, venous thrombosis (VT), arterial thrombosis (AT) were compared to healthy donors (n=60). The percentages of patients above cut-off were highest in the SAPS, SLE and SLE+aPL groups. Significant differences were observed between healthy donors and inflammatory groups of patients (SAPS and SLE+aPL) in all three measured parameters. SAA and CRP were shown to be correlated to a greater extent in SAPS patients than SLE+aPL patients. In summary, this cross-sectional, retrospective, small study and accompanying clinical considerations limit the ability to make definite conclusions. SAA would not serve as a useful marker for venous, arterial thrombosis or PAPS (pro-coagulant events). It could however, be a good predictor of progression from a non-inflammatory thrombotic condition to an inflammatory one.

Avidity of anti-beta-2-glycoprotein I antibodies.

The terms affinity and avidity are often used indiscriminately, despite clearly differing. Since affinity refers to monovalent binding of antibodies to a monovalent epitope, the majority of data on the binding of anti-beta2-glycoprotein I antibodies (anti-beta2-GPI) characterized their avidity rather than affinity. Anti-beta2-GPI were generally believed to be of low avidity, but heterogeneous avidity of patients' IgG anti-beta2-GPI has been demonstrated. High avidity anti-beta2-GPI monoclonals were reported to possess higher pathogenicity than low avidity anti-beta2-GPI. Polyclonal high avidity anti-beta2-GPI were found to be more common in patients with antiphospholipid syndrome (APS) and associated with thrombosis. Some conformational changes of beta2-GPI are required for the binding of polyclonal anti-beta2-GPI to the antigen: neither high density of the antigen nor high avidity of the anti-beta2-GPI alone is sufficient for the recognition. Avidity of anti-beta2-GPI should be considered in any attempt of inter-laboratory standardisation and/or evaluation of anti-beta2-GPI enzyme-linked immunosorbent assay (ELISA).

Avidity of anti-beta2-glycoprotein I and thrombosis or pregnancy loss in patients with antiphospholipid syndrome.

We aimed to evaluate avidity of anti-beta(2)-glycoprotein I antibodies (anti-beta(2)-GPIs) in patients with antiphospholipid syndrome (APS) at the time of acute thrombotic events or pregnancy loss as compared with clinical event-free periods. To do so, 69 sera samples from 16 patients (6 with primary APS and 10 with APS secondary to systemic lupus erythematosus ) were selected on the basis of anti-beta(2)-GPI positivity. Avidity of IgG anti-beta(2)-GPIs was determined by chaotropic enzyme-linked immunosorbent assay (ELISA), using increased NaCl concentration during antibody binding. High, heterogeneous, and low-avidity anti-beta(2)-GPIs were measured in APS patients, with no clear pattern regarding the time of thrombotic events or pregnancy failure. In general, anti-beta(2)-GPI avidity did not change substantially during disease course. We concluded that avidity of anti-beta(2)-GPIs appears to be a rather stable parameter in an individual APS patient. Considering the previously shown association of high-avidity anti-beta(2)-GPIs with venous thrombosis, avidity of anti-beta(2)-GPIs may be a better predictor of predisposition to thrombosis and unsuccessful pregnancy than levels of antiphospholipid antibodies, which may fluctuate over time owing to several factors.

The use of adenovirus-infected HeLa cells for the detection of low titer autoantibodies.

Following infection of HeLa cells with adenovirus type 5 the cellular La protein becomes predominantly associated with the virally encoded RNA polymerase III products VAI, and VAII, while most of the host RNA polymerase II (e.g. U1, U2, U4, U5 and mRNA) and RNA polymerase III transcription (e.g. U6 and pre-tRNAs) ceases. Other RNA polymerase III products such as the cellular Ro RNAs continue to be transcribed and assembled into ribonucleoprotein complexes containing the Ro (SS-A) antigens. Using a 32P-pulse chase-labeled, adenovirus-infected HeLa cellular extract as a source of antigen, anti-La (SS-B) and anti-Ro (SS-A) antibodies can be detected simultaneously using an immunoprecipitation assay. In the present study this method was found to be more sensitive in detecting anti-La antibodies then counter immunoelectrophoresis and immunoblotting. In studies of sera from patients suffering from rheumatic diseases the percentage positive for anti-La antibody was significantly elevated using this method, especially in patients with systemic lupus erythematosus.

Prevalence of antiphospholipid antibodies in deep vein thrombosis and their relationship to blood coagulation and fibrinolysis.

Elevated levels of antiphospholipid antibodies are associated with an increased risk of thrombosis. To establish the prevalence of these antibodies in deep vein thrombosis (DVT), IgG and IgM antibodies to cardiolipin (aCL) and phosphatidylserine (aPS) were determined by enzyme-linked immunosorbent assay in 118 patients with DVT either during an acute episode (N = 53) or at least 2 months after acute DVT (N = 65). Most patients (76%) had proximal leg DVT and no one had evident autoimmune disorder. aCL and aPS values higher than 4 standard deviations above the mean value of the control group (147 blood donors) were considered increased. Increased IgG aCL were observed in 10% of DVT patients (controls: 5%, not significant), increased IgG aPS in 16% of DVT patients (controls: 5%, p less than 0.005) and both types in 4% of DVT patients (controls: 3%, not significant). In the subgroup of 41 patients with previous idiopathic DVT, prevalence of increased IgG aPS was the highest: 27% (p less than 0.001). Increased antibodies of IgM isotype were observed in 3% (aCL) and 2% (aPS) of all DVT patients (controls: 8% and 4%, respectively, not significant). Elevated IgG aCL or aPS were not associated with significant changes in platelet count, antithrombin III and protein C. However, in patients with increased IgG aPS deficient fibrinolysis due to high plasminogen activator inhibitor activity was observed before and after 20 min upper arm venous occlusion. DVT patients with increased IgG aPS might be exposed to a greater risk of rethrombosis due to deficient fibrinolysis than DVT patients without these antibodies.

Fluctuation of anti-Ro/SS-A antibody levels in patients with systemic lupus erythematosus and Sjögren's syndrome: a prospective study.

OBJECTIVE: To determine whether the titers of anti-Ro/SS-A (Ro) antibodies fluctuate during the course of SLE and Sjögren's syndrome (SS) in parallel with disease activity, and if such fluctuations could be used to predict disease flares. We also evaluated whether the anti-Ro profile (anti-Ro 52, anti-Ro 60) changes over time, since such information could provide new insights into the induction and regulation of anti-Ro autoimmunity. METHODS: Sixteen patients with SLE and 15 patients with SS, all anti-Ro/SS-A antibody positive, were followed up for two years at three-month intervals. Clinical and laboratory parameters of disease activity were examined. Determination of the anti-Ro/SS-A titer was performed by counterimmunoelectrophoresis and the fine anti-Ro antibody specificity was determined by immunoblotting. RESULTS: The titers of anti-Ro antibodies fluctuated during the course of the illness in both SLE and SS patients. In SLE patients these changes were not (except in one case) associated with disease activity nor were they predictive of disease flares. The same was true for the SS patients, with the exception of two patients with skin vasculitis in whom anti-Ro antibody titers fluctuated in parallel with the disease activity. The anti-Ro antibody (anti-Ro 60 kD, anti-Ro 52 kD) specificity did not change in any of the patients during the follow-up period. CONCLUSION: Anti-Ro antibodies could represent a valuable indicator of disease activity in SS patients with cutaneous disorders. They do not, on the other hand, reflect disease activity in patients with SLE. The stable antibody profile in both SLE and SS patients supports the hypothesis that autoantibody production is predominantly genetically regulated.

Estimation of anticardiolipin antibodies, anti-beta2 glycoprotein I antibodies and lupus anticoagulant in a prospective longitudinal study of children with juvenile idiopathic arthritis.

OBJECTIVE: Anticardiolipin antibodies (aCL) have been frequently detected in juvenile idiopathic arthritis (JIA), but have not been associated with disease activity or clinical features of the antiphospholipid syndrome (APS). Our aim was to determine aCL and anti-beta2 glycoprotein I (anti-beta2GPI) antibody levels and lupus anticoagulant (LA) in serial samples from children with JIA and to investigate the clinical significance of these antibodies. METHODS: The values of aCL, anti-beta2GPI and LA were prospectively followed in 28 children with JIA from disease onset. aCL and anti-beta2GPI were assayed by an ELISA method. Two monoclonal beta2GPI-dependent aCL (HCAL and EY2C9) were used as calibrators. LA was determined by a modified dilute Russell viper venom time test. RESULTS: Thirteen (46.4%) children with JIA were already positive for aCL at their first referral to our center. During the follow-up, the frequency of aCL decreased from 46.4% to 28.6%; however, it remained significantly higher compared with healthy children. In contrast, for anti-beta2GPI the difference in the frequency between the children with JIA and healthy children was not statistically significant. Serial determination of aPL levels in JIA patients revealed frequent fluctuations. Positive aCL persisted over time in 6 (21.4%) children with JIA, 6 (21.4%) children were initially positive for aCL, but became later negative, and 3 (10.7%) children were initially negative for aCL and became later positive. Persistently positive anti-beta2GPI were observed during the follow-up only in one patient, while none of the patients was persistently positive for LA. No association between aCL, anti-beta2GPI or LA and disease activity could be established. No patient with positive aCL, anti-beta2GPI or LA showed any clinical feature of APS. CONCLUSION: The discrepancy between the presence of aCL and anti-beta2GPI might indicate that the production of aCL in JIA is associated with an infectious trigger. Furthermore, the low frequency of anti-beta2GPI and LA could explain the limited prothrombotic potential of aPL observed in JIA. However, we found a distinct group of JIA patients with persistently positive aCL, the clinical implications of which are at the present time unknown.

Immunoserological aspects of idiopathic inflammatory muscle disease.

In the present study, the autoantibody profile of 31 Slovenian patients with idiopathic inflammatory muscle disease was estimated: 11 with polymyositis, 11 with dermatomyositis--both groups diagnosed according to the criteria of Bohan and Peter--and 9 with myositis-overlap syndromes. Autoantibodies against most relevant muscle specific (Jo-1, Mi-2) and non-specific antigens (PM-Scl, U1RNP, native Ro, Ro60, Ro52, and La) were detected with one or more detection techniques: counter-immunoelectrophoresis, enzyme-linked immunoassay, immunoblot and immunoprecipitation, each using different antigen preparations (native, recombinant). With counter-immunoelectrophoresis using a native antigen substrate (rabbit thymus extract), we were able to detect anti-PM-Scl antibodies more readily than with other techniques, probably due to conformational epitopes of native PM-Scl. Patients with this serological profile constituted a distinct group, sharing features of polymyositis and systemic sclerosis. Compared to previously reported data, the greater frequency of anti-Jo-1 found in all groups of patients (64-87% for PM, 18-20% for dermatomyositis and 33-44% for overlap syndromes) was probably due to the various methods used and the different clinical characteristics of patients. The greater prevalence of anti-Mi-2 antibodies in dermatomyositis patients (67%) and in particular in polymyositis patients (33%) and myositis-overlap syndromes (33%) seemed to be mainly due to methodological differences. A strikingly high prevalence of anti-Ro52 positive patients with polymyositis (55%), dermatomyositis (22%), and myositis-overlap syndromes (33%) was demonstrated, but was detected by only one technique. Moreover, concurrence with anti-Jo-1 antibodies was noted (69%).

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

BACKGROUND: Diagnosis of the antiphospholipid syndrome (APS) is difficult as a result of limited specificity of existing assays for detecting clinically relevant antiphospholipid antibodies. Anti-beta2-glycoprotein I (beta 2GPI) antibodies play a central role in the disease process of APS. OBJECTIVES: We have investigated the relation between antiphospholipid antibodies with specificity for domain I of beta 2GPI and thrombosis/pregnancy morbidity in an international multicenter study. PATIENTS/METHODS: Four hundred and seventy-seven patients derived from nine different centres met the inclusion criterion of having anti-beta 2GPI antibodies in their plasma/serum. Clinical data and results of tests for lupus anticoagulant, anti-cardiolipin antibodies and anti-beta 2GPI antibodies were established at the different centres of inclusion. After being re-tested for the presence of IgG and/or IgM anti-beta 2GPI antibodies, the samples were tested for the presence of IgG-directed against domain I of beta 2GPI and results were correlated with the thrombotic and obstetric history. RESULTS: Re-testing for the presence of anti-beta 2GPI antibodies resulted in inclusion of 442/477 patients. IgG class anti-domain I antibodies were present in plasma of 243/442 patients (55%). 201/243 (83%) had a history of thrombosis. This resulted in an odds ratio of 3.5 (2.3-5.4, 95% confidence interval) for thrombosis. Anti-domain I IgG antibodies were also significantly correlated with obstetric complications [odds ratio: 2.4 (1.4-4.3, 95% confidence interval)]. CONCLUSION: In this multicenter study, the detection of IgG antibodies that are directed against domain I of beta 2GPI proved to be more strongly associated with thrombosis and obstetric complications than those detected using the standard anti-beta 2GPI antibody assay.