Invitation to a debate on the serological criteria that define the antiphospholipid syndrome

Semiquantitative interpretation of anticardiolipin and antiβ2glycoprotein I antibodies measured with various analytical platforms: Communication from the ISTH SSC Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibodies

BACKGROUND

Antiβ2glycoprotein I (aβ2GPI) and anticardiolipin (aCL) IgG/IgM show differences in positive/negative agreement and titers between solid phase platforms. Method-specific semiquantitative categorization of titers could improve and harmonize the interpretation across platforms.

AIM

To evaluate the traditional 40/80-unit thresholds used for aCL and aβ2GPI for categorization into moderate/high positivity with different analytical systems, and to compare with alternative thresholds.

MATERIAL AND METHODS

aCL and aβ2GPI thresholds were calculated for two automated systems (chemiluminescent immunoassay [CLIA] and multiplex flow immunoassay [MFI]) by receiver operating characteristic curve analysis on 1108 patient samples, including patients with and without antiphospholipid syndrome (APS), and confirmed on a second population (n = 279). Alternatively, regression analysis on diluted standard material was applied to identify thresholds. Thresholds were compared to 40/80 threshold measured by an enzyme-linked immunosorbent assay (ELISA). Additionally, likelihood ratios (LR) were calculated.

RESULTS

Threshold levels of 40/80 units show poor agreement between ELISA and automated platforms for classification into low/moderate/high positivity, especially for aCL/aβ2GPI IgG. Agreement for semiquantitative interpretation of antiphospholipid antibodies (aPL) IgG between ELISA and CLIA/MFI improves with alternative thresholds. LR for aPL IgG increase for thrombotic and obstetric APS based on 40/80 thresholds for ELISA and adapted thresholds for the other systems, but not for IgM.

CONCLUSION

Use of 40/80 units as medium/high thresholds is acceptable for aCL/aβ2GPI IgG ELISA, but not for CLIA and MFI. Alternative semiquantitative thresholds for non-ELISA platforms can be determined by a clinical approach or by using monoclonal antibodies. Semiquantitative reporting of aPL IgM has less impact on increasing probability for APS.

Antiphospholipid patterns predict risk of thrombosis in systemic lupus erythematosus

OBJECTIVE

We evaluated which aPL combinations increase the risk of future thrombosis in patients with SLE.

METHODS

This prospective cohort study consisted of SLE patients who had been tested for all seven aPL (LA, aCL isotypes IgM, IgG and IgA, and anti-β2-glycoprotein I isotypes IgM, IgG and IgA). Pooled logistic regression was used to assess the relationship between aPL and thrombosis.

RESULTS

There were 821 SLE patients with a total of 75 048 person-months of follow-up. During the follow-up we observed 88 incident cases of thrombosis: 48 patients with arterial, 37 with venous and 3 with both arterial and venous thrombosis. In individual models, LA was the most predictive of any [age-adjusted rate ratio 3.56 (95% CI 2.01, 6.30), P < 0.0001], venous [4.89 (2.25, 10.64), P < 0.0001] and arterial [3.14 (1.41, 6.97), P = 0.005] thrombosis. Anti-β2-glycoprotein I IgA positivity was a significant risk factor for any [2.00 (1.22, 3.3), P = 0.0065] and venous [2.8 (1.42, 5.51), P = 0.0029] thrombosis. Only anti-β2-glycoprotein I IgA appeared to add significant risk to any [1.73 (1.04, 2.88), P = 0.0362] and venous [2.27 (1.13, 4.59), P = 0.0218] thrombosis among those with LA. We created an interaction model with four categories based on combinations of LA and other aPL to look at the relationships between combinations and the risk of thrombosis. In this model LA remained the best predictor of thrombosis.

CONCLUSION

Our study demonstrated that in SLE, LA remained the best predictor of thrombosis and adding additional aPL did not add to the risk, with the exception of anti-β2-glycoprotein I IgA.

Anti-phospholipid antibodies and reproductive failures

Anti-phospholipid syndrome (APS) recapitulates the link between autoimmunity and pregnancy failure: Acquired anti-phospholipid antibodies (aPL) play a pathogenic role in pregnancy complications. The diagnosis of obstetric APS can easily be pursued when women present with laboratory and clinical features fulfilling the international classification criteria. Standard therapeutic approach to obstetric APS consists in the association of anti-platelet agents and anticoagulants. Most patients achieve a live birth thanks to conventional treatment; however, approximately 20% fail to respond and are managed with additional therapeutic tools added on the top of conventional treatment. Surely, a refinement of risk stratification tools would allow early identification of high-risk pregnancies that warrant tailored treatment. In real life, obstetricians and rheumatologists face complex diagnostic scenarios including women with pregnancy morbidities other than those mentioned in classification criteria such as one or two early losses and premature birth after 34 weeks due to preeclampsia or placental insufficiency, women with low-titer aPL not fulfilling criteria laboratory requirements, women with positive non-criteria aPL, asymptomatic aPL carriers, and infertile women found to be aPL-positive. This review focuses on some of the several unanswered questions related to diagnostic, prognostic, and therapeutic aspects in obstetric APS.

The (non-)sense of detecting anti-cardiolipin and anti-β2glycoprotein I IgM antibodies in the antiphospholipid syndrome

BACKGROUND

The antiphospholipid syndrome (APS) is characterized by thrombosis and/or pregnancy morbidity with the persistent presence of lupus anticoagulant (LAC), anti-cardiolipin (aCL) and/or anti-β2glycoprotein I (aβ2GPI) antibodies of the immunoglobulin G/immunoglobulin M (IgG/IgM) isotype. However, the role of aCL and aβ2GPI IgM as a serologic marker in APS is debated.

OBJECTIVES

We aimed to assess the diagnostic and clinical value of IgM antiphospholipid antibodies (aPL) in APS within the classification criteria.

PATIENTS/METHODS

Our multicenter study comprised 1008 patients, including APS patients and controls. Anti-CL and aβ2GPI IgG and IgM antibodies were detected with four commercially available solid phase assays.

RESULTS

Positivity for aCL and/or aβ2GPI antibodies was significantly correlated with thrombosis and pregnancy morbidity, independent of the isotype and solid phase assay. Higher odds ratios were obtained for IgG compared to IgM positivity. Isolated IgM was rare in thrombotic APS, but more frequent in obstetric APS, ranging from 3.5% to 5.4% and 5.7% to 12.3%, respectively, dependent on the solid phase assay. In a multivariate logistic regression analysis of aPL, IgM positivity was found to be associated with pregnancy morbidity. However, detection of IgM was not independently associated with thrombosis. Combined positivity for LAC, IgG, and IgM was highly associated with thrombosis and pregnancy morbidity.

CONCLUSIONS

Our data support testing for aCL and aβ2GPI IgM in women suspected of obstetric APS. However, no added value was found for testing IgM in patients suspected of thrombotic APS. Still, IgM aPL might be useful as a second-line test to improve thrombotic risk stratification.

Utility of Lupus Anticoagulant Assays (APTT-LA, KCT, DPT and DRVVT) in Detection of Antiphospholipid Syndrome (APS) in High Risk Pregnancy Cases

Routine investigation for recurrent pregnancy loss includes measurement of antiphospholipid antibodies. The lupus anticoagulant has long been associated with increased risks for thrombosis and adverse obstetric outcomes. But there are some disadvantages with lupus anticoagulant (LAC) tests which includes varied sensitivity of different clot based assays. ISTH recommends only 2 assays (preferably DRVVT and APTT-LA) for the identification of lupus anticoagulant but there are some studies which don't support this contention. Our study analyzed 526 samples from high risk pregnancy cases for APLA by all four LAC tests from tertiary centre of northern India. Among all the cases studies 65 cases were positive for lupus anticoagulant 25 of this became negative after 12 weeks. Among the 40 repeated positive assays, dRVVT could able to diagnose 36 cases followed by APTT-LA which could able to diagnose 28 cases, while KCT could able to diagnose 23 cases and dPT could able to diagnose only 14 cases. There were 12 cases in whom all lupus assays were positive. Our study thus concluded that DRVVT was the most sensitive followed by APPT-LA, KCT, dPT. The combination of dRVVT with APTT-LA or KCT appeared to be superior to other combinations. No individual test per se is 100% sensitive for the diagnosis of APLA in high risk pregnancy cases. Further results confirmed that repeated LAC result is required even in a high-risk setting. Positive LAC assay in majority were not associated with exclusively recurrent pregnancy loss but were associated with sporadic stillbirth and thrombosis.

Diagnosis and management of non-criteria obstetric antiphospholipid syndrome

Accurate diagnosis of obstetric antiphospholipid syndrome (APS) is a prerequisite for optimal clinical management. The international consensus (revised Sapporo) criteria for obstetric APS do not include low positive anticardiolipin (aCL) and anti β2 glycoprotein I (aβ2GPI) antibodies (> 99th centile) and/or certain clinical criteria such as two unexplained miscarriages, three non-consecutive miscarriages, late preeclampsia, placental abruption, late premature birth, or two or more unexplained in vitro fertilisation failures. In this review we examine the available evidence to address the question of whether patients who exhibit non-criteria clinical and/or laboratory manifestations should be included within the spectrum of obstetric APS. Prospective and retrospective cohort studies of women with pregnancy morbidity, particularly recurrent pregnancy loss, suggest that elimination of aCL and/or IgM aβ2GPI, or low positive positive aCL or aβ2GPI from APS laboratory diagnostic criteria may result in missing the diagnosis in a sizeable number of women who could be regarded to have obstetric APS. Such prospective and retrospective studies also suggest that women with non-criteria obstetric APS may benefit from standard treatment for obstetric APS with low-molecular-weight heparin plus low-dose aspirin, with good pregnancy outcomes. Thus, non-criteria manifestations of obstetric APS may be clinically relevant, and merit investigation of therapeutic approaches. Women with obstetric APS appear to be at a higher risk than other women of pre-eclampsia, placenta- mediated complications and neonatal mortality, and also at increased long-term risk of thrombotic events. The applicability of these observations to outcomes in women with non-criteria obstetric APS remains to be determined.

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.

Relationship between antiphosphatidylserine/prothrombin and conventional antiphospholipid antibodies in primary antiphospholipid syndrome

BACKGROUND

Antiphosphatidylserine/prothrombin complex (aPS/PT) antibodies are emerging as an important marker for antiphospholipid syndrome (APS). We aimed to compare their performance with that of conventional antiphospholipid antibodies (aPL) such as lupus anticoagulant (LA), anticardiolipin (aCL), and anti-β2-glycoprotein I (anti-β2GPI) in APS and to assess their frequency in APS-negative (APS-ne) patients.

METHODS

We considered 160 APS patients and 128 APS-ne patients with clinical criteria for APS but tested negative for conventional aPL. Immunoglobulin (Ig)G/IgM aPS/PT, IgG/IgM aCL, and IgG/IgM anti-β2GPI were detected using ELISA assay and LA with a series of coagulation tests.

RESULTS

IgG aPS/PT were significantly associated with IgG aCL, IgG anti-β2GPI, and LA (p<0.0001 for all). IgM aPS/PT were significantly associated only with LA (p<0.0001) instead. There was a significant correlation between IgG aPS/PT and both IgG aCL and IgG anti-β2GPI levels (ρ=0.42 and ρ=0.40, respectively). Both IgG aPS/PT and IgM aPS/PT positivity significantly correlated with LA (ρ=0.44 and ρ=0.5, respectively). IgG and IgM aPS/PT were significantly more frequent in triple than in double and in single positivity (p<0.0001). According to multivariate analysis, IgG and/or IgM aPS/PT were independent risk factors for LA. APS/PT antibodies were found in 9.4% of the APS-ne patients vs. 2% of healthy control (p=0.043); those antibodies were significantly more frequent in the thrombosis with respect to the pregnancy morbidity subset (p=0.01).

CONCLUSIONS

Our data attribute a clinical relevance to both IgG and IgM aPS/PT antibodies. In particular, the significant prevalence of aPS/PT in APS-ne patients suggests including them as additional laboratory criterion for APS.

The clinical performance of a chemiluminescent immunoassay in detecting anti-cardiolipin and anti-β2 glycoprotein I antibodies. A comparison with a homemade ELISA method

BACKGROUND

Fully automated chemiluminescence immunoassays (CLIAs) are emerging technologies for the detection of anti-cardiolipin (aCL) and anti-β2 glycoprotein I (anti-β2GPI) antibodies for anti-phospholipid syndrome (APS) classification, which is commonly based on an enzyme-linked immunosorbent assay (ELISA) test result. CLIA and a homemade ELISA were used in this study to detect these antibodies, and their performances were compared.

METHODS

Sera were collected from 104 patients with primary APS, 88 seronegative subjects who met the clinical but not the laboratory criteria for APS, and 150 control subjects. IgG/IgM aCL and IgG/IgM anti-β2GPI antibodies were determined in the sera using a CLIA (HemosIL AcuStar®) and a homemade ELISA.

RESULTS

CLIA had a significantly lower comparative sensitivity for IgM aCL and IgG/IgM IgG anti-β2GPI antibodies; its comparative specificity was higher with respect to ELISA for IgM aCL and IgM anti-β2GPI antibodies. The two techniques showed a high, significant agreement (p<0.001) and a significant titer correlation (p<0.001). CLIA also detected IgG/IgM aCL and IgG anti-β2GPI antibodies in the seronegative patients. There was a significantly higher prevalence of IgG aCL and IgG anti-β2GPI antibodies (p<0.001 and p=0.01, respectively) in those patients with respect to that in the control population.

CONCLUSIONS

Despite a lower comparative sensitivity, CLIA showed a higher comparative specificity for some aPL and a good level of agreement and correlation with a homemade ELISA. CLIA also detected some aCL and anti-β2GPI antibodies in the seronegative patients not usually identified by homemade ELISA.

Frequency of vascular and pregnancy morbidity in patients with low vs. moderate-to-high titers of antiphospholipid antibodies

Antiphospholipid syndrome (APLS) is an autoimmune hypercoagulable syndrome characterized by thrombotic and obstetric manifestations. We sought to determine the rate of APLS feature in patients tested positive for antiphospholipid antibodies (APLA) regardless of the serum level of anticardiolipin (ACL) and/or anti-β2-glycoprotein I (β2GPI) antibodies. An inception cohort of individuals who were tested positive for ACL and/or β2GPI IgG/IgM antibody, and/or lupus anticoagulant (LAC) on two occasions of at least 12 weeks apart. A total of 243 patients were included; their mean age was 40.1 ± 15.9 years. Thrombotic vascular events occurred in 118 patients (48.5%) of the entire cohort, of which 62 patients (25.5%) suffered from an arterial event and 56 patients (23%) from thrombotic venous events. Obstetrical morbidity occurred in 106 female patients (43.6%). In our cohort, we found no difference in the frequency of thrombotic or obstetric manifestations of APLS between patients with ACL IgG/IgM of low serum antibody level (<40 U) and medium-to-high level (≥40 U) and/or anti-β2GPI IgG, IgM higher than the 99th percentile vs. lower (>20 U). We suggest that in 'real life' the diagnosis of APLS should not be excluded because of low titer of APLA.

The clinical relevance of the IgM isotype of antiphospholipid antibodies in the vascular antiphospholipid syndrome

OBJECTIVES

Because it has been suggested that the IgM isotype of antiphospholipid (aPL) antibodies should no longer be included in the laboratory criteria for antiphospholipid syndrome (APS) classification, we assess the clinical relevance of IgM isotype of aPL in a cohort of patients with vascular APS.

PATIENTS/METHODS

Mean age, sex, the presence of autoimmune diseases other than systemic lupus erythematosus, risk factors for thrombosis, the type/s and site/s of thromboembolic events, the levels of C3 and C4, and autoantibody profile were evaluated in a large cohort of persistently aPL positive patients fulfilling the Sydney criteria for APS. Patients with isolated IgM isotype were compared for each variable with those with any other aPL antibody combination.

RESULTS

One hundred six patients were assessed; of these 55 (51.9%) had venous thromboembolism, 48 (45.3%) arterial thrombosis, and 3 (2.8%) small vessel thrombosis. Positivity to only IgM aPL made possible to classify 13 patients (12.3%) as vascular APS. In all cases the presence of IgM aPL was at medium-high titer, confirmed, and found to be stable in the time. There were four patients with retinal thrombosis (3.8%) and the prevalence of this event was significant in the isolated IgM isotype positive patients (p=0.005).

CONCLUSIONS

Data from this investigation give clinical value to the IgM isotype of aPL and suggest to consider aCL and anti-β2GPI of IgM class as valid laboratory criteria for APS classification, especially when they are associated and stable overtime.

A contribution to detection of anticardiolipin and anti-β2glycoprotein I antibodies: Comparison between a home-made ELISA and a fluorescence enzyme immunoassay

BACKGROUND

Currently, ELISA for detection of anticardiolipin (aCL) and anti-β2glycoprotein I (anti-β2GPI) antibodies is not standardized. Recently, few studies have compared the performance of ELISA with that of fluorescence enzyme immunoassay (FEIA), but they have produced debatable results. The aim of this investigation was to compare ELISA with FEIA results in detecting aCL and anti-β2GPI antibodies.

METHODS

The study cohort included 94 primary antiphospholipid syndrome (PAPS) patients, 65 subjects with the clinical criteria for PAPS classification but ELISA negative for the laboratory criteria and 165 control subjects. Serum IgG/IgM aCL/anti-β2GPI antibodies were determined using FEIA-EliA™ and a home-made ELISA.

RESULTS

The sensitivities of the two methods were similar with the exception of IgM aCL which was found to be significantly higher in the PAPS patients using the ELISA method, even if IgM aCL was detected at a low level by both techniques. The two assays had a comparable specificity, a high/significant agreement and a significant correlation between the antibody levels. FEIA testing uncovered no significant prevalence of any antiphospholipid (aPL) antibody in the ELISA negative patients.

CONCLUSION

Our results suggest that FEIA is comparable to a home-made ELISA.

Antiphospholipid antibodies: evaluation of the thrombotic risk

The laboratory diagnosis of the antiphospholipid syndrome (APS) via antiphospholipid antibody (aPL) tests, including lupus anticoagulant (LAC), anti-cardiolipin (aCL), or anti-beta2 glycoprotein I (aβ2GPI) antibodies remains a challenge. Coagulation tests for LAC as well as solid phase assays for aCL and aβ2GPI have methodological shortcomings, although for LAC large progress have been made in standardization. All assays are associated with clinical APS-criteria (thrombotic and/or pregnancy complications) but with limited specificity. Besides, clinical studies demonstrating the association between the presence of aPL and thrombosis are not always well designed and result in wide ranges of odds ratio with large variation between studies. The best association between thrombotic complications and aPL is found for LAC. The association between thrombosis and aCL or aβ2GPI is at least inconsistent. The inclusion of more specific assays, such as the domain-I-β2GPI.antibodies is too premature and depends on further investigation in large clinical studies and the commercial availability. The search for new assays should proceed to identify patients with aPL with increased risk for thrombosis, preferable in large prospective studies. Meanwhile, with the current available LAC, aCL and aβ2GPI assays it is strongly recommended to make antibody profiles. Multiple positivity of tests seems clinically more relevant. The strengths and weaknesses of the current laboratory criteria for APS are discussed in view of their role in risk stratification of patients with thrombotic events.

Diagnosis of antiphospholipid syndrome in routine clinical practice

The updated international consensus criteria for definite antiphospholipid syndrome (APS) are useful for scientific clinical studies. However, there remains a need for diagnostic criteria for routine clinical use. We audited the results of routine antiphospholipid antibodies (aPLs) in a cohort of 193 consecutive patients with aPL positivity-based testing for lupus anticoagulant (LA), IgG and IgM anticardiolipin (aCL) and anti-ß₂glycoprotein-1 antibodies (aß₂GPI). Medium/high-titre aCL/aβ₂GPI was defined as >99th percentile. Low-titre aCL/aβ₂GPI positivity (>95^th< 99^th percentile) was considered positive for obstetric but not for thrombotic APS. One hundred of the 145 patients fulfilled both clinical and laboratory criteria for definite APS. Twenty-six women with purely obstetric APS had persistent low-titre aCL and/or aβ₂GPI. With the inclusion of these patients, 126 of the 145 patients were considered to have APS. Sixty-seven out of 126 patients were LA-negative, of whom 12 had aCL only, 37 had aβ₂GPI only and 18 positive were for both. The omission of aCL or aβ₂GPI testing from investigation of APS would have led to a failure to diagnose APS in 9.5% and 29.4% of patients, respectively. Our data suggest that LA, aCL and aβ₂GPI testing are all required for the accurate diagnosis of APS and that low-titre antibodies should be included in the diagnosis of obstetric APS.

Efficacy of the antiphospholipid score for the diagnosis of antiphospholipid syndrome and its predictive value for thrombotic events

OBJECTIVE

To define the antiphospholipid score (aPL-S) by testing multiple antiphospholipid antibodies (aPL) and to evaluate its efficacy for the diagnosis of antiphospholipid syndrome (APS) and predictive value for thrombosis.

METHODS

This study comprised 2 independent sets of patients with autoimmune diseases. In the first set of patients (n = 233), the aPL profiles were analyzed. Five clotting assays for testing lupus anticoagulant and 6 enzyme-linked immunosorbent assays (IgG/IgM anticardiolipin antibodies, IgG/IgM anti-β(2)-glycoprotein I, and IgG/IgM phosphatidylserine-dependent antiprothrombin antibodies) were included. The association of the aPL-S with a history of thrombosis/pregnancy morbidity was assessed. In the second set of patients (n = 411), the predictive value of the aPL-S for thrombosis was evaluated retrospectively. Two hundred ninety-six of these patients were followed up for >2 years. The relationship between the aPL-S and the risk of developing thrombosis was analyzed.

RESULTS

In the first set of patients, the aPL-S was higher in those with thrombosis/pregnancy morbidity than in those without manifestations of APS (P < 0.00001). For the aPL-S, the area under the receiver operating characteristic curve value was 0.752. In the second set of patients, new thromboses developed in 32 patients. The odds ratio (OR) for thrombosis in patients with an aPL-S of ≥30 was 5.27 (95% confidence interval [95% CI] 2.32-11.95, P < 0.0001). By multivariate analysis, an aPL-S of ≥30 appeared to be an independent risk factor for thrombosis (hazard ratio 3.144 [95% CI 1.383-7.150], P = 0.006).

CONCLUSION

The aPL-S is a useful quantitative index for diagnosing APS and may be a predictive marker for thrombosis in autoimmune diseases.

Síndrome antifosfolípide e trombocitopenia na infância

OBJETIVO: Relatar o caso de uma criança com diagnóstico de síndrome do anticorpo antifosfolípide associada à trombocitopenia grave e realizar uma revisão de literatura sobre o assunto. DESCRIÇÃO DO CASO: Criança de nove anos e oito meses de idade com trombocitopenia grave associada a anticorpo anticardiolipina positivo. Os dados foram coletados por meio de anamnese, exame físico e exames complementares da paciente. O diagnóstico foi determinado de acordo com os critérios estabelecidos para a síndrome antifosfolípide, associados às manifestações mais comuns na faixa etária pediátrica: livedo reticular e trombocitopenia. COMENTÁRIOS: A síndrome do anticorpo antifosfolípide é uma doença incomum na população pediátrica e suas manifestações clínicas, com a redução do número de plaquetas, devem ser consideradas.

Lupus anticoagulant: performance of the tests as recommended by the latest ISTH guidelines

OBJECTIVES

Lupus anticoagulant (LA) is clinically the most relevant among all antiphospholipid antibody tests. Recently, new guidelines for LA detection were published. The objective of this retrospective cohort study was to compare tests recommended under these guidelines with other methods used for LA detection.

METHODS

The study group consisted of 336 subjects suffering from various autoimmune diseases. We used activated partial thromboplastin time (aPTT), diluted Russell viper venom time (dRVVT) and diluted prothrombin time (dPT) tests for LA detection together with a ratio between sensitive and insensitive aPTT reagent. We also tested if LA was dependent on β(2) glycoprotein I (β(2) GPI) using one of the recently described methods.

RESULTS

All LA tests performed were associated with a history of thrombosis. The highest odds ratio (OR) for thrombosis was found for β(2) GPI-dependent LA but sensitivity was low (OR = 8.4; specificity/sensitivity = 98%/15%). All LA tests showed a much stronger association with thrombosis than with pregnancy failure.

CONCLUSIONS

LA tested by aPTT and/or dRVVT (at least one out of two tests positive), as recommended by the guidelines, was associated less strongly with a history of thrombosis (OR = 4.1) than either of these tests separately (OR = 5.0 and 4.3, respectively). With both tests positive ('double LA positivity') the association with thrombosis was stronger (OR = 6.5) compared with only one positive test. In fact, 'double LA positivity', detected by combinations of any of the tests studied, was markedly associated with a history of thrombosis.

Evaluation of a new set of automated chemiluminescense assays for anticardiolipin and anti-beta2-glycoprotein I antibodies in the laboratory diagnosis of the antiphospholipid syndrome

INTRODUCTION

The laboratory diagnosis of antiphospholipid syndrome (APS) requires the demonstration of antiphospholipid antibodies (aPL): lupus anticoagulant (LAC) measured through coagulation assays, anticardiolipin IgG or IgM antibodies (aCL) and/or anti-β2glycoprotein I IgG or IgM antibodies (aβ2GPI), usually detected by ELISA.

MATERIALS AND METHODS

We evaluated the diagnostic value of aCL and aβ2GPI measured by a new automated system using the chemiluminescence principle, the immunoanalyzer Zenit RA (Menarini).

RESULTS

Results of aCL and aβ2GPI were correlated with the clinical background of the patients and with results of ELISA (n=314). Correlated to the clinical background sensitivity/specificity ranged for aCL IgG between 7.5-45.2% / 54.2-98.8%, for aCL IgM 3.4-5.5% / 89.9-94%, for aβ2GPI IgG 5.5-25.3% / 75.6-100% and aβ2GPI IgM 3.4-4.8% / 89.9-92.3%, depending on the cut-off used. Sensitivity with manufacturer's cut-offs was comparable to ELISA, except for aβ2GPI IgG with a significantly lower sensitivity compared to ELISA (5.5% vs 11.6%). In the APS patient population (n=30) sensitivity of aCL IgG and aβ2GPI IgG was higher measured by ELISA compared to Zenit RA (46.7% vs 30.0%, and 46.7% vs 26.7%, respectively). Agreement between Zenit RA results and ELISA results for the four parameters was moderate (Kappa-values ranging 0.509-0.565). Sensitivity was 38.5%, 53.3%, 40% and 69.2% for aCL IgG, aCL IgM, aβ2GPI IgG and aβ2GPI IgM, respectively, applying the highest cut-off value for Zenit RA, raising towards 64.3%, 100%, 57.1%, for aCL IgG, aCL IgM, aβ2GPI IgG, respectively, in a APS patient population.

CONCLUSIONS

The new technology of chemiluminescense for measuring aPL showed good performance characteristics. Interpretation of results with a cut-off value associated with a good discrimination for disease, resulted in a lower sensitivity for the diagnosis of APS for aβ2GPI IgG measured by Zenit RA assays compared to ELISA; sensitivity for aCL IgG was comparable to ELISA. Specificity for all parameters was high and comparable for aCL and aβ2GPI.

Laboratory testing for the antiphospholipid syndrome: making sense of antiphospholipid antibody assays

The antiphospholipid syndrome (APS) is an autoimmune condition characterised by a wide range of clinical features (primarily thrombosis and/or obstetric related), associated with the presence of antiphospholipid antibodies (aPL) as detected by a diverse range of laboratory tests. APS remains a significant diagnostic challenge for clinicians across a wide range of specialities, largely due to issues related to laboratory testing as well as the expanding range of reported clinical manifestations of APS. The laboratory issues include limitations in detailed knowledge by both clinical and laboratory personnel regarding the 'complete' range of available aPL tests, as well as ongoing problems with assay reproducibility and standardisation. aPL are identified using diverse laboratory procedures based on one of two distinct test processes, namely solid phase and liquid phase assays. The former includes anticardiolipin antibodies (aCL) and anti-β(2)-glycoprotein I antibodies (aβ(2)GPI). The latter are centred on clot-based tests that are used to identify the so-called lupus anticoagulant (LA). This article will discuss: (i) issues related to laboratory testing for APS in terms of the currently available solid-phase and liquid-phase assays, and identifiable biases resulting from these tests usually being performed in different laboratories; (ii) current problems with calibration, standardisation and reproducibility of these assays; (iii) pre-analytical, analytical and post-analytical considerations and ongoing initiatives for improvement; (iv) issues related to potential combinations/panels of available aPL tests; and (v) the entities of seropositive APS, seronegative APS and non-APS aPL-positivity. In doing so, this review will hopefully help bridge the two disciplines of haematology and immunology ('representing' liquid-phase and solid-phase aPL testing, respectively), by improving the understanding of those working in each of these disciplines of the merits and limitations of the assays performed in the other discipline, and encouraging inter-discipline cooperation in the reporting of aPL test results.

Antiphospholipid antibodies--we are not quite there yet

The diagnosis of antiphospholipid syndrome is predominantly made in the laboratory and depends on the persistent presence of antiphospholipid antibodies in individuals with thrombosis or pregnancy morbidity. Correct diagnosis of the syndrome is imperative to prevent unnecessary long secondary thromboprophylaxis. Three antiphospholipid antibody subtypes are included in the classification criteria of the antiphospholipid syndrome: lupus anticoagulants, anticardiolipin antibodies and anti-β2-glycoprotein I antibodies. Only lupus anticoagulants are undisputedly associated with thrombosis, which is why the serological criteria of the antiphospholipid syndrome are under debate. All of the assays used to detect antiphospholipid antibodies are in need of better standardization, although progress has been made in the detection of lupus anticoagulants. The inconsistent association between both anticardiolipin and anti-β2-glycoprotein I antibodies and thrombosis is a cause for alarm. We are in need of better assays to detect those individuals at risk for thrombosis and population-based prospective studies to provide us with accurate risk assessments.

A review of hereditary and acquired coagulation disorders in the aetiology of ischaemic stroke

The diagnostic workup in patients with ischaemic stroke often includes testing for prothrombotic conditions. However, the clinical relevance of coagulation abnormalities in ischaemic stroke is uncertain. Therefore, we reviewed what is presently known about the association between inherited and acquired coagulation disorders and ischaemic stroke, with a special emphasis on the methodological aspects. Good-quality data in this field are scarce, and most studies fall short on epidemiological criteria for causal inference. While inherited coagulation disorders are recognised risk factors for venous thrombosis, there is no substantial evidence for an association with arterial ischaemic stroke. Possible exceptions are the prothrombin G20210A mutation in adults and protein C deficiency in children. There is proof of an association between the antiphospholipid syndrome and ischaemic stroke, but the clinical significance of isolated mildly elevated antiphospholipid antibody titres is unclear. Evidence also suggests significant associations of increased homocysteine and fibrinogen concentrations with ischaemic stroke, but whether these associations are causal is still debated. Data on other acquired coagulation abnormalities are insufficient to allow conclusions regarding causality. For most coagulation disorders, a causal relation with ischaemic stroke has not been definitely established. Hence, at present, there is no valid indication for testing all patients with ischaemic stroke for these conditions. Large prospective population-based studies allowing the evaluation of interactive and subgroup effects are required to appreciate the role of coagulation disorders in the pathophysiology of arterial ischaemic stroke and to guide the management of individual patients.

Recurrent miscarriage and antiphospholipid antibodies: prognosis of subsequent pregnancy

BACKGROUND

 Although women with antiphospholipid antibodies (APLAs) are at increased risk of recurrent miscarriage, the outcome of a subsequent pregnancy is not clearly elucidated.

OBJECTIVES

To assess the pregnancy outcome of a subsequent pregnancy in women with APLAs and compare this outcome with women with unexplained recurrent miscarriage.

METHODS

 We performed a cohort study among all women who attended the Miscarriage Clinic at Liverpool Women's Hospital between 1987 and 2006 after being referred due to recurrent miscarriage (≥2 consecutive pregnancy losses). All women underwent a standardized investigation sequence. Women with other reasons for recurrent miscarriage were excluded.

RESULTS

 A total of 693 women fulfilled the selection criteria, of whom 176 (25%) had APLAs. One hundred and twenty-two (69%) women with APLAs had a subsequent live birth compared with 324 (63%) women with unexplained recurrent miscarriage (OR 1.3, 95% CI 0.9-1.9). No differences were found for birth weight, gestational age, and intra-uterine growth restriction. When treatment was analyzed, 53/67 (79%) of women with APLAs who had received aspirin and heparin during their pregnancy had a live birth, compared with 64/104 (62%) of women with APLAs who received aspirin only (adjusted OR 2.7, 95% CI 1.3-5.8). In unexplained recurrent miscarriage, stratification for treatment showed no differences in outcome.

CONCLUSION

The prognosis of a subsequent pregnancy in women with APLAs is good. Although this was not a randomized clinical trial, combined treatment of aspirin and heparin seemed associated with a better outcome in women with APLAs, but not in women with unexplained recurrent miscarriage.

Evaluation of three commercial ELISA kits for anticardiolipin and anti-beta2-glycoprotein I antibodies in the laboratory diagnosis of the antiphospholipid syndrome

INTRODUCTION

The laboratory criteria of the antiphospholipid syndrome (APS) include lupus anticoagulant (LAC), anticardiolipin antibodies (aCL) and anti-β2glycoprotein I antibodies (aβ2GPI) IgG or IgM.

METHODS

We evaluated three commercial ELISAs for aCL and aβ2GPI IgG and IgM: Asserachrom® ('Stago'), Bio-Rad ('BR') and the Bindazyme™ (the Binding Site, 'BS').

RESULTS

Results of all assays and of LAC were correlated with the clinical background (n=228). Sensitivity for Stago/BS/BR aCL IgG was 14%/15%/18%, for aCL IgM 1%/5%/4%, for aβ2GPI IgG 9%/10%/17% and for aβ2GPI IgM 4%/4%/3%. The specificity for Stago/BS/BR for all assays ranged from 86% to 98%. The positive predictive value (PPV) for Stago/BS/BR aCL IgG was 46%/52%/40%, for aCL IgM 8%/36%/19%, for aβ2GPI IgG 70%/67%/45% and for aβ2GPI IgM 23%/23%/20%. Combining LAC with aCL and aβ2GPI antibodies increased the sensitivity (Stago/BS/BR IgG: 26%/27%/31%, IgM: 22%/21%/26%) and PPV (Stago/BS/BR IgG: 41%/46%/36%, IgM: 34%/40%/36%). Comparing the diagnostic power of the tests, only Stago/BS aβ2GPI IgG had a Chi-square P-value lower than 0.05. The combination of LAC and IgG ELISAs of BS resulted in the lowest P-value (0.098) compared to the other combinations.

CONCLUSION

All evaluated ELISAs are a practical tool in the laboratory diagnosis of APS. The diagnostic performance shows slight differences between the ELISAs from the different manufacturers.

The antiphospholipid syndrome: a large elephant with many parts or an elusive chameleon disguised by many colours?

The antiphospholipid syndrome (APS) is characterized by a range of clinical features (primarily thrombosis and/or obstetric-related), together with the presence of antiphospholipid antibody (aPL) as detected by a diverse range of laboratory tests. APS remains a significant diagnostic and management challenge for clinicians across a wide range of specialties, some 30 years after APS was first described as a discrete clinical entity. This is due to ongoing issues regarding nomenclature, the diagnosis of APS in individual patients, the expanding range of recognized clinical manifestations and of APS-related laboratory tests, and management issues in particular APS patient subgroups (including obstetric and catastrophic APS). In addition to the presence of appropriate clinical features, the diagnosis of APS fundamentally requires the finding of positive aPL test result(s), which is hampered by ongoing problems with assay reproducibility and standardization. This review focuses on ongoing dilemmas and issues related to clinical and laboratory aspects of APS including: (1) diagnostic challenges posed by the protean clinical manifestations of APS; (2) current nomenclature and recent proposals for revision of the 2006 international classification criteria; (3) an overview of some key issues related to aPL testing; (4) potential pitfalls of applying the APS classification criteria as diagnostic criteria; and (5) the controversial subgroups of seronegative APS and non-APS aPL positivity.

Analytical and clinical performance of a new, automated assay panel for the diagnosis of antiphospholipid syndrome

SUMMARY BACKGROUND

Anticardiolipin (aCL) and anti-beta(2)glycoprotein I (abeta(2)GPI) antibodies are part of the criteria for antiphospholipid syndrome (APS). Therefore they are widely measured and about 30 commercial kits are available.

OBJECTIVES

To investigate the analytical and clinical performances of four fully automated, chemiluminescent assays: HemosIL AcuStar aCL IgG, HemosIL AcuStar aCL IgM, HemosIL AcuStar abeta(2)GPI IgG, and HemosIL AcuStar abeta(2)GPI IgM.

METHODS

Cut-off values were assessed by testing 250 blood donors. Total coefficients of variation (CV) were determined with six plasma pools and two controls ranging from 4.3 to 2694 U mL(-1) depending on the assay. Samples from 218 well-characterized patients and 103 controls were measured in three laboratories to determine inter-laboratory variation. The results of the 321 samples were compared with three commercial assays (REAADS, INOVA and VARELISA).

RESULTS

Cut-off values were assigned to 20 arbitrary units for all the tests. Total CV ranged from 4.3 to 11.2%. No interference of hemoglobin, bilirubin, triglycerides, heparins and rheumatoid factor was observed. Inter-laboratory variability was low and no sample changed status. Overall status agreement between HemosIL assays and the comparator kits ranged from 82 to 96%. Sensitivity, specificity, agreement when predicting APS and the odds ratios when predicting a thrombotic or obstetric event gave comparable results between HemosIL AcuStar and the three other assays.

CONCLUSIONS

Our study demonstrates that the fully automated HemosIL AcuStar aPL assay panel showed similar performances to the three commercial ELISAs commonly used by various laboratories to detect antiphospholipid antibodies.

Standardized antigen preparation to achieve comparability of anti-beta2-glycoprotein I assays

INTRODUCTION

The Sydney classification for diagnosis of the antiphospholipid syndrome (APS) first introduced the determination of anti-beta2-glycoprotein I (anti-beta2-GPI)-antibodies in serum as laboratory criteria. In this context, widely differing results of anti-beta2-GPI assays are a concerning issue. Considerable efforts have been made to optimize ELISAs, however little attention was hitherto spent to the antigen preparation. We evaluated the influence of different beta2-GPI preparations on the ability to separate ill and healthy patients and on the comparability of anti-beta2-GPI-assays.

MATERIALS AND METHODS

Microplates were coated with various beta2-GPI preparations and anti-beta2-GPI IgG- and IgM-ELISAs were performed for 21 APS patients and 21 controls using the monoclonal calibrators HCAL and EY2C9. Subsequently, by use of a surface plasmon resonance (SPR) biosensor, affinity constants for the HCAL- and EY2C9-interaction with each beta2-GPI preparation were determined and antigen binding of sera of APS patients and controls was studied.

RESULTS

All ss2-GPI preparations showed good discrimination ability ill vs. healthy but poor inter-assay comparability in the ELISAs. Affinity constants for HCAL and EY2C9 were independent of the beta2-GPI variant (K(A) 0.105 - 0.200 and 0.449 - 1.04 x 10(10)M(-1); K(D) 50.0 - 95.5 and 9.61 - 22.3 x 10(-11)M, respectively). In the biosensor, reactivity to the different beta2-GPIs was negligible for the controls and varied considerably for patients.

CONCLUSION

Inter-assay comparability of anti-beta2-GPI ELISAs is highly dependent upon the beta2-GPI preparation. Only agreement on one common beta2-GPI preparation will improve the requested inter-assay comparability.

Challenges in the Diagnosis of the Antiphospholipid Syndrome

Background: The antiphospholipid syndrome (APS) is an important cause of acquired thromboembolic complications and pregnancy morbidity. Its diagnosis is based on clinical and laboratory criteria, defined by strict guidelines. The original clinical and laboratory criteria for the identification of APS patients were published in 1999, in the so-called Sapporo criteria. In 2006 these criteria were revised, and recently more precise guidelines for analysis of the lupus anticoagulant have been provided. However, several questions related to the diagnosis of APS remain unanswered.

Content: In addition to providing a historical perspective, this review covers several challenges in the diagnosis of APS with respect to clinical and laboratory features, while highlighting pathogenic pathways of the syndrome. We discuss ongoing dilemmas in the diagnosis of this complex disease. Although antiphospholipid antibodies are found in association with various clinical manifestations, the older established clinical criteria were not substantively altered in the 2006 update. Several laboratory tests recommended in the latest criteria, including phospholipid-dependent coagulation tests for the detection of the lupus anticoagulant and ELISAs for measuring anticardiolipin and β2-glycoprotein I antibodies, still show methodological and diagnostic shortcomings. In addition, antiphospholipid antibodies have been described against other antigens, but their clinical role remains uncertain.

Conclusions: Despite updated APS criteria, diagnosis of this syndrome remains challenging. Further research on clinically relevant antibodies and standardization of their detection are needed to improve clinical risk assessment in APS.

Observational study of pregnant women with a previous spontaneous abortion before the 10th gestation week with and without antiphospholipid antibodies

BACKGROUND

A clinical subtype of purely obstetrical antiphospholipid antibody (aPL-Ab) syndrome (APS) requires three or more unexplained consecutive embryonic losses before the 10th week of gestation associated with persistently positive lupus anticoagulant (LAC), and/or anticardiolipin IgG or IgM, and/or anti-beta2-glycoprotein I (abeta2GpI) IgG or IgM. Although this diagnostic classification of APS appeared to be the most sensitive, the APS-associated serological criteria are still debated.

PATIENTS/METHODS

We prospectively observed the second pregnancy of 284 women with a previous embryonic loss, both with and without aPL-Ab.

RESULTS

aPL-Ab-positive women were more prone to pregnancy loss, embryonic loss, pre-eclampsia, placental abruption and intrauterine fetal growth restriction. Type IIa aPL-Ab positivity (LAC present alone) was associated with the highest risk of recurrent embryonic loss and intrauterine growth restriction. Type I aPL-Ab positivity (combinations of aPL-Ab type positivity) was associated with the strongest risks of late complications, pre-eclampsia and placental abruption. Finally, abeta2GpI-M positivities were not clinically relevant in these women.

CONCLUSION

Patients with a first unexplained pregnancy loss before the 10th week of gestation who are also positive for aPL-Abs have a higher risk of various complications in their second pregnancy. In this study, measurement of abeta2GpI-M had a questionable prognostic value.

Antiphospholipid antibody profile: implications for the evaluation and management of patients

According to the classification criteria of antiphospholipid syndrome, lupus anticoagulant, anticardiolipin and anti-β2 glycoprotein I antibody assays are independent risk factors for the occurrence of vascular thrombosis and pregnancy loss. However, it is generally accepted that patients carrying multiple positivity have more a severe disease and higher recurrence rate despite treatment. On the other hand, the diagnostic value of a positive result in one only assay is more controversial, particularly in the presence of clinical manifestations such as deep vein thrombosis or early miscarriages, which are rather common in the general population. In this review we speculate on current and future strategies to interpret different antiphospholipid antibody profiles in the clinical practice. Lupus (2010) 19, 432—435.

The association of antiphospholipid antibodies with pregnancy-related first time venous thrombosis--a population-based case-control study

In this population-based case-control study we explored the association of antiphospholipid antibodies with pregnancy-related venous thrombosis. From 1990 through 2003 615 pregnant women were identified at 18 hospitals in Norway with a diagnosis of first time VT. In 2006, 531 of 559 eligible cases and 1092 of 1229 eligible controls were invited for further investigations. The final study population comprised 313 cases and 353 controls, who completed a comprehensive questionnaire and donated a single blood sample, 3-16 years after index pregnancy. We report the results on lupus anticoagulant, anticardiolipin antibodies, and anti-ss(2) glycoprotein-1 antibodies alone, in combination, and with the contribution of the factor V Leiden and the prothrombin gene G20210A polymorphisms. Cut-off values for APAs were chosen according to current international consensus. 29 (9.3%) of the cases and 24 (6.8%) of the controls had at least one positive test for APAs (OR 1.4; 95% CI 0.8-2.5). Nine cases (2.8%) and no controls had more than one positive test (multi-positivity) for APAs. After excluding women with factor V Leiden or prothrombin polymorphisms, still 6 cases were multi-positive for APAs. We conclude that multi-positivity, but not single-positivity, for APAs was weakly associated with a history of ante- and postnatal VT.

Moderate versus high-titer persistently anticardiolipin antibody positive patients: are they clinically different and does high-titer anti-beta 2-glycoprotein-I antibody positivity offer additional predictive information?

The association between antiphospholipid antibodies (aPL) and clinical events is stronger with a positive lupus anticoagulant (LA) test, higher anticardiolipin antibody (aCL) titers, and/or higher anti-beta(2)-glycoprotein-I antibody (abeta( 2)GPI) titers. The objective of this study was to determine the clinical characteristics of persistently high-titer (> or =80 U) aCL-positive patients compared with those with persistent moderate aCL titers (40-79 U). Second, we analyzed whether high-titer abeta(2)GPI test adds predictive information in persistently moderate-to-high titer aCL-positive patients. In this cross-sectional study, the primary analysis compared the clinical and aPL characteristics of 58 patients with at least two moderate-titer aCL results to another 85 patients with at least two high-titer aCL results. In the secondary analysis of patients with at least two abeta(2)GPI test results, we compared 29 patients with 'aCL 40-79 U and abeta( 2)GPI < 80 U' profiles with 8 patients with 'aCL 40-79U and abeta(2)GPI > or = 80 U', and also compared 27 patients with 'aCL > 80 U and abeta(2)GPI < 80 U' with 32 patients with 'aCL > 80 U and abeta(2)GPI > or = 80 U'. Although aPL-related vascular and pregnancy events were similar between the moderate- and high-titer aCL groups, the number of patients with positive LA tests (RR 2.06, CI 1.38-3.08, p < 0.01) and with at least one non-criteria aPL manifestation (RR 1.66, CI 1.20-2.30, p = 0.0005) were significantly higher in the high-titer aCL group. While magnetic resonance imaging (MRI) white matter changes were statistically more common in the high-titer aCL group (RR 2.03, CI 1.04-3.94, p = 0.02), there was a trend towards increased prevalence of livedo reticularis, cardiac valve disease, and cognitive dysfunction occurring in the high-titer aCL group. The secondary analysis showed that MRI white matter changes, cardiac valve disease, and cognitive dysfunction were proportionally more common in the high-titer abeta( 2)GPI groups, suggesting a linear relationship between non-criteria aPL manifestations and aPL titers. Our results suggest that patients with high aCL titers, compared with those with moderate titers, are more likely to have a positive LA test and a higher prevalence of non-criteria aPL manifestations. Furthermore, high-titer abeta(2)GPI positivity may further increase the prevalence of non-criteria aPL manifestations in moderate- or high-titer aCL-positive patients.

Antiphospholipid syndrome review

The antiphospholipid syndrome (APS) is an autoimmune disorder presenting with tissue injury in various organs attributed to large or small vessel thrombosis or, in some instances, possible nonthrombotic inflammatory mechanisms, associated with in vitro evidence of antibodies to certain proteins, or proteinphospholipid complexes. Although the pathophysiology, diagnosis, and management of APS may seem clear and straightforward from a distance, closer inspection reveals a more complex, incomplete, and uncertain image. This article reviews the evolution of APS from the first description of lupus anticoagulant to the current criteria used to guide clinical research, critiques laboratory methods used to identify autoantibodies, comments on prognosis and management, and summarizes insights into the pathophysiology of this elusive disorder.

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.

European registry of babies born to mothers with antiphospholipid syndrome: a result update

The registry is a prospective, European, multicentric, longitudinal study, which follows a cohort of children born to mothers with antiphospholipid syndrome (APS). It was started in 2003. In this report, we update the results obtained from the study of 110 mothers and 112 children (two twin births). Eighty per cent of the mothers (n = 86) had primary APS. Purely obstetrical, thrombotic and mixed (obstetrical and thrombotic) APS represent 65.5 %, 21.8 % and 12.7 % of the whole cohort respectively. Isolated antiphospholipid antibodies and isolated anticardiolipin antibodies positivity were present in 50 of 109 (46%) and in 34 of 109 (31%) of the pregnant women, respectively. In the babies, in spite of a high rate of prematurity (14.3%) with four (3.6%) of the premature babies born before 33 weeks of gestation and an increased number of newborns small for gestational age (17%), the large majority of the neonates were healthy. Thirty-one infants are now older than 24 months. Among them, three displayed behavioural abnormalities before 3 years of age. After completing data, there will be the possibility to evaluate the newborn status in relation to the mothers' diseases, treatments and antibodies and to follow the neuropsychological development and immunological evolution of the babies during the next 5 years.

Mechanisms of antiphospholipid-induced thrombosis: effects on the protein C system

An acquired resistance to activated protein C (APC) has been demonstrated in patients with antiphospholipid antibodies (aPL). Recent studies report interactions between beta2 glycoprotein I (beta2GPI) and prothrombin-binding antibodies and the protein C system. Some aPL in patients recognize one or more conformational epitopes shared by beta2GPI and catalytic domains of APC. Both beta2GPI and anti-prothrombin antibodies are associated with APC resistance. Several clinical studies have focused on an association between aPL and APC resistance, determined by classic activated partial thromboplastin time-based tests. It has been shown in most studies that APC resistance was associated with lupus anticoagulants. APC resistance is also associated with thrombosis, especially venous thromboembolism. Several recent studies have reported a novel integrated approach of coagulation using calibrated automated thrombography. This technique allows an approach of APC sensitivity without interference with lupus anticoagulants. Clinical associations between APC resistance and thromboembolic events have been demonstrated.