Is the determination of anti-beta2 glycoprotein I antibodies useful in patients with venous thromboembolism without the antiphospholipid syndrome?

IgA Antiphospholipid Antibodies in Antiphospholipid Syndrome and Systemic Lupus Erythematosus

Objective: To define the role of IgA antibodies to cardiolipin (aCL) and IgA antibodies to beta-2 glycoprotein 1 (anti-β2-GP1) in the development of vascular complications in patients with antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE). Material and methods: A total of 187 patients with one of the following diagnoses: primary APS (PAPS), probable APS, SLE with APS, and SLE without APS. The comparison group consisted of 49 patients with other rheumatic diseases (RD), the control group included 100 relatively healthy individuals (without RD, oncological pathology, and infectious diseases). All patients underwent standard clinical, laboratory, and instrumental examinations before being included in the study and during follow-up. The aPL study included the determination of IgG/IgM aCL, IgG/IgM anti-β2-GP1 by enzyme-linked immunosorbent assay (ELISA), IgG/IgM/IgA aCL, IgG/IgM/IgA anti-β2-GP1 by chemiluminescence analysis (CLA), and lupus anticoagulant (LA). Results: IgA aCL were detected in 75 (40%) of the 187 patients with APS and SLE, in none of the comparison group, and in 2 (2%) of the control one. IgA anti-β2-GP1 were detected in 63 (34%) of the 187 patients with APS and SLE, in none of the patients in the comparison group, and in one (1%) of the control group. The prevalence of IgA aCL and IgA anti-β2-GP1 and their levels were statistically significantly higher in patients with APS (PAPS and SLE + APS) than the levels in patients with SLE and those of the comparison and control groups (p < 0.05). IgA aCL and IgA anti-β2-GP1 were significantly associated with thrombosis in APS (χ2 = 4.96; p = 0.02 and χ2 = 4.37; p = 0.04, respectively). The risk of thrombosis was 2.04 times higher in patients with positive IgA aCL than in patients without these antibodies, as well as in patients with positive IgA anti-β2-GP1; it was twice as high as in patients without antibodies. There was a high specificity of IgA aCL and IgA anti-β2-GP1 for both the diagnosis of APS and its clinical manifestations, despite a low sensitivity. Conclusions: The study revealed a relationship of thrombosis and APS with IgA aCL and IgA anti-β2-GP1. There was a high specificity of IgA aCL and IgA anti-β2-GP1 (95% and 93%, respectively) for the diagnosis of APS with a low sensitivity (54% and 44%, respectively). There were no patients with isolated positivity of IgA aCL and IgA anti-β2-GP1.

Immunoglobulin A Isotype of Antiphospholipid Antibodies Does Not Provide Added Value for the Diagnosis of Antiphospholipid Syndrome in a Chinese Population

Objective

Antiphospholipid syndrome (APS) is characterized by the presence of anti-phospholipid (aPL) antibodies. However, the relationship between the immunoglobulin (Ig) A isotype of aPL positivity and its clinical utility in APS diagnosis is controversial. Presently, we determine the clinical utility of IgA-aPL from consecutive patients in a large cohort from the Chinese population and patients with APS whose aPL profiles were obtained.

Methods

The detection of anticardiolipin (aCL) and anti-β₂ glycoprotein-Ⅰ (aβ₂GPⅠ) antibodies of the IgA/IgG/IgM isotype by paramagnetic particle chemiluminescent immunoassay was carried out in sera from 7293 subjects. 153 primary APS (PAPS) patients and 59 patients with secondary APS (SAPS) were included in this study.

Results

In total, 1,082 out of 7,293 (2.55%) subjects had a positive IgA-aPL test, and the prevalence of isolated IgA-aPL was 0.29% (21/7,293) in the general population. The prevalence of IgA-aPL in the PAPS patients was 12.42% (19/153); however, only one patient (0.65%) presented with isolated IgA-aPL. Fifty (25.9%) of the SAPS had IgA-aPL, none of whom lacked IgG/IgM-aPL. The combination of the IgA isotype and the IgG/IgM isotype did not increase the diagnostic performance when compared with the IgG/IgM isotype of aCL or aβ₂GPⅠ, respectively. IgA-aPL was not associated with clinical manifestation in patients with APS.

Conclusion

Isolated IgA-aPL is rare in the general population as well as in patients with APS. Whether in the laboratory or in clinical practice, the presence of IgA-aPL does not provide added value for the diagnosis of APS in the Chinese population.

IgG/IgM antiphospholipid antibodies present in the classification criteria for the antiphospholipid syndrome: a critical review of their association with thrombosis

Essentials The clinical value of IgM antibodies in thrombotic antiphospholipid syndrome (APS) is debated. By review of literature, we reconsidered the clinical value of IgM antibodies in thrombotic APS. More significant correlations with thrombosis were found for the IgG compared to IgM isotype. Unavailability of paired IgG/IgM results hampers evaluating the added value of IgM positivity. Click to hear Dr de Groot's perspective on antiphospholipid syndrome

SUMMARY

Background Despite the update of the classification criteria for the antiphospholipid syndrome (APS), difficulties persist in the identification of patients at risk for thrombosis. Current guidelines include assays detecting IgG/IgM anti-β2 -glycoprotein I and anti-cardiolipin antibodies, although the relevance of IgM antibodies has been debated. Objectives Through a review of the literature from 2001 to 2014, we aimed to formally establish the thrombotic risk stratification potential of IgM as compared with IgG anti-phospholipid antibodies (aPLs). Patients/methods One thousand two hundred and twenty-eight articles were selected by a computer-assisted search of the literature. Of the 177 studies that met our inclusion criteria, the clinical value of IgG/IgM aPLs was established through analysis of odds ratios for thrombosis or percentage of positives in the thrombotic population. Results/conclusions We clearly found more significant correlations with thrombosis for the IgG than for the IgM isotype. Nonetheless, in a minority of studies, significant associations with thrombosis were found for IgM but not IgG antibodies. The unavailability of paired results of IgG and IgM for each separate patient hampers evaluation of the added value of isolated IgM positivity. To fully take advantage of results obtained by future studies, we strongly encourage scientists to provide all studied information per patient. We planned a large multicenter study to investigate clinical associations of isolated/combined positivity for criteria/non-criteria aPLs. Importantly, because of the presence of non-pathogenic aPLs, quantitative assays are characterized by a high false-positivity rate. Optimization of functional assays, such as thrombin generation measuring the whole scheme of coagulation, may help to reduce APS-related morbidity and mortality.

The clinical relevance of IgA anticardiolipin and IgA anti-β2 glycoprotein I antiphospholipid antibodies: a systematic review

The antiphospholipid syndrome (APS) is diagnosed in patients with thromboembolic events and/or pregnancy loss in the presence of persistent laboratory evidence for antiphospholipid antibodies (aPL). Diagnostic tests for the detection of antiphospholipid antibodies include laboratory assays that detect anticardiolipin antibodies, lupus anticoagulants, and anti-β(2)-glycoprotein I antibodies. Most studies on aPL have mainly focused on the estimation of the IgG and IgM isotypes, with only a few studies reporting on the pathogenic significance of IgA aPL. In this review we aimed to summarize and analyze the evidence published in the literature on the prevalence and the clinical significance of IgA aPL.

Lupus anticoagulant is significantly associated with inflammatory reactions in patients with suspected deep vein thrombosis

OBJECTIVE

Lupus anticoagulant (LA) and antiphospholipid antibodies (aPL) are suggested as risk factors for development of deep vein thrombosis (DVT) among patients without systemic lupus erythematosus (SLE). Other conditions, e.g. inflammation, are reported to induce LA and it is uncertain whether the association between LA and DVT is causal. In this study the associations between aPL, LA and inflammation were investigated in 170 consecutive patients without SLE, but with a tentative diagnosis of DVT.

MATERIAL AND METHODS

DVT was diagnosed in 64 patients. LA was determined according to the criteria of the International Society of Thrombosis and Haemostasis. The concentration of anticardiolipin (aCL) and beta(2)-glycoprotein I (anti-beta(2)-GPI) antibodies as well as C-reactive protein (CRP) was determined with sensitive and precise methods.

RESULTS

LA was demonstrated in 8 patients with DVT and in 10 patients without DVT, relative risk 1.33 (CI: 0.55-3.18). No significant association was observed between aCL or anti-beta(2)-GPI and DVT. Patients suffering from DVT had significantly higher concentrations of CRP than patients without DVT. However, CRP was also significantly higher in patients positive for LA than in patients without LA irrespective of the presence of DVT (p<0.001).

CONCLUSIONS

The present study supports a strong association between inflammatory reactions and development of LA in patients with suspected DVT, whereas no significant association was demonstrated between LA or aPL and DVT.

The presence of IgG antibodies against beta2-glycoprotein I predicts the risk of thrombosis in patients with the lupus anticoagulant

BACKGROUND

Lupus anticoagulant (LA) is a strong risk factor of thrombosis. However, a subgroup of patients positive for LA is unaffected by thrombosis and currently no predictive markers are available to identify patients positive for LA at increased risk for thrombosis.

OBJECTIVE

The aim of the study was to investigate whether anti-beta-2-glycoprotein I (anti-beta2GPI) or anticardiolipin antibodies (ACA) are associated with an increased risk of thrombosis in patients persistently positive for LA.

PATIENTS AND METHODS

A cohort of 87 consecutive patients persistently positive for LA was investigated, 55 with and 32 without a history of thrombosis. Immunoglobulin G (IgG) and M (IgM) antibodies against beta2GPI and cardiolipin were determined by enzyme-linked immunoassay.

RESULTS

Patients positive for LA with thrombosis had significantly higher levels of anti-beta2GPI IgG (median 16.7 standard units, interquartile range 3.0-75.2, P = 0.002) and of ACA IgG (41.1 IgG phospholipid units per mL, 8.9-109.0, P = 0.002) than those without thrombosis (2.6, 1.4-7.9 and 9.7, 4.6-22.1, respectively). Levels of anti-beta2GPI IgM and ACA IgM did not differ significantly between LA patients with and without thrombosis (P = 0.25 and 0.12, respectively). Elevated anti-beta2GPI IgG was associated with an increased risk for thrombosis (OR = 4.0, 95% CI 1.2-13.1), especially for venous thromboembolism (OR = 5.2, 95% CI 1.5-18.0).

CONCLUSIONS

Increased levels of anti-beta2GPI IgG were associated with thrombosis. We conclude that anti-beta2GPI IgG levels above normal predict an increased risk of thrombosis in patients persistently positive for LA.

Prevalence and Clinical Correlation of Anti-Phospholipid–Binding Protein Antibodies in Anticardiolipin-Negative Patients With Systemic Lupus Erythematosus and Women With Unexplained Recurrent Miscarriages

Context.—Anti-phospholipid antibodies (aPL) are a heterogeneous group of autoantibodies, the presence of which is associated with thrombotic events and miscarriage.

Objective.—To establish whether antibodies directed against phospholipid-binding plasma proteins such as β2-glycoprotein I (β2GPI), prothrombin (PT), and annexin V (Anx V) constitute a risk factor for thromboembolism in patients with systemic lupus erythematosus (SLE) and for miscarriage in women with recurrent pregnancy loss (RPL), independently of the presence of the classic anticardiolipin (aCL) antibodies, and whether their determination together with that of aCL would help to increase the diagnostic sensitivity of aPL tests.

Design.—The prevalence of various antibodies directed toward phospholipids (CL and other anionic phospholipids [APL]) and phospholipid-binding proteins (β2GPI, PT, and Anx V) was determined by immunoenzymatic methods in 311 serum samples.

Patients.—Twenty-five patients with aCL-positive primary anti-phospholipid syndrome (pAPS); 89 patients with SLE, 23 of whom had thrombotic complications (SLE/APS) and 66 of whom had no thrombosis; and 77 women with unexplained recurrent pregnancy loss comprised our study group. One hundred twenty healthy subjects matched for age and sex were studied as the control group.

Results.—Immunoglobulin (Ig) G and/or IgM aAPL, anti-β2GPI, anti-PT, and IgG anti-Anx V antibodies were detected in 25 (100%), 20 (80%), 15 (60%), and 6 (24%), respectively, of the 25 aCL-positive pAPS patients; IgG and/or IgM aCL, aAPL, anti-β2GPI, anti-PT, and IgG anti-Anx V antibodies were detected in 33 (37%), 42 (47%), 31 (35%), 40 (45%), and 12 (13%) of the 89 SLE patients, respectively. Of the 56 SLE patients who proved to be aCL negative, anti-β2GPI was present in 3 patients (5%), anti-PT in 13 (23%) patients, and anti-Anx V in 5 (9%) patients. In the subset of 23 SLE/APS patients, IgG anti-PT prevalence was higher than that of the other autoantibodies (87% vs 70% aCL, 66% aAPL, 57% anti-β2GPI, and 4% anti-Anx V), and in 26% of cases, IgG anti-PT was the only antibody present. Anti-PT had a slightly lower specificity than aCL (46% vs 49%); however, the occurrence of both antibodies brought the specificity to 92.4%. The highest risk for thrombosis in SLE patients was associated with the presence of IgG anti-PT antibody (odds ratio [OR] 15.3, P &lt; .001, vs 6.5 aCL, 3.5 aAPL, 3.4 anti-β2GPI, 0.2 anti-Anx V). Fifty-one of the 77 women with recurrent pregnancy loss were negative for all antibodies investigated; the prevalence of IgG and/or IgM aCL, aAPL, anti-β2GPI, anti-PT, and IgG anti-Anx V antibodies was 6% (5), 12% (9), 6% (5), 16% (12), and 17% (13), respectively. Of the 67 aCL-negative women, none had anti-β2GPI antibodies, 7 (11%) were anti-PT positive, and 13 (19%) were anti-Anx V positive. In the subgroup of 26 recurrent pregnancy loss patients who had at least one antibody, anti-Anx V was present in 50% of cases (in 42% as the sole antibody) and was the only antibody significantly associated with miscarriage (P = .02).

Conclusions.—The results of this study indicate that it is useful to measure anti-PT antibodies in addition to the more widely used aCL and anti-β2GPI antibodies in the prognostic evaluation of SLE patients for the risk of thrombosis, and the results also confirm that anti-Anx V antibodies may play an important role in recurrent pregnancy loss.

Anti-β2-glycoprotein I antibodies—When and how should they be measured?

The biological criteria of the antiphospholipid syndrome defined at the Sapporo meeting in 1998 included the presence of lupus anticoagulant (LA) and/or anticardiolipin antibodies at medium and high titers. During the 48th SSC meeting held in Boston July 2002, it was proposed to modify these criteria. Four patient groups were defined, the first one comprising LA and anti-beta2glycoprotein I antibodies (abeta2GPI), the second one LA only, the third one abeta2GPI only and the fourth one other antiphospholipid antibodies such as antiprothrombin, anticardiolipin, antiphosphatidylethanolamine, etc. This proposition raised the issue of the association of abeta2GPI with APS clinical criteria (thrombosis and pregnancy morbidity). In some studies, a strong association between IgG abeta2GPI and thrombosis was found, whereas in others this association could not be demonstrated. In the obstetrical field, few studies are available and no clear conclusion can be drawn yet. However, for thrombosis or pregnancy morbidity, it has been shown that in up to 10% of patients, abeta2GPI are the sole antibodies present and therefore the diagnosis of APS would be missed in these patients. In addition, some studies suggest that the severity of disease is dependent on the number of positive tests and on their titers. We recommend abeta2GPI assays to be included in the panel of antiphospholipid screening tests. However, the standardisation of abeta2GPI assays has to be improved in order to ensure better comparability between the studies.