Minimal requirements for antiphospholipid antibodies ELISAs proposed by the European Forum on antiphospholipid antibodies

Establishment of ELISA-comparable moderate and high thresholds for anticardiolipin and anti-β2 glycoprotein I chemiluminescent immunoassays according to the 2023 ACR/EULAR APS classification criteria and evaluation of their diagnostic performance

OBJECTIVES

Recently published 2023 ACR/EULAR APS classification criteria emphasize the importance of quantifying single-, double-, and triple-antiphospholipid antibody positivity, distinguishing between IgG and IgM isotypes, and delineating moderate/high levels of anticardiolipin (aCL) and anti-β2 glycoprotein I (anti-β2GPI) antibodies. We aimed to establish clinically important moderate/high thresholds for aCL and anti-β2GPI IgG/IgM chemiluminescent immunoassays (CLIA), in particular QUANTA Flash, comparable to our in-house ELISAs used for over two decades, and to evaluate their diagnostic performance.

METHODS

QUANTA Flash CLIA and in-house ELISAs were used to measure aCL and anti-β2GPI IgG/IgM. Moderate thresholds for QUANTA Flash CLIA were determined using a non-parametric approach, calculating a 99th percentile on serum samples from 139 blood donors, and by mirroring the diagnostic performance of in-house ELISA on 159 patient samples.

RESULTS

Thresholds for QUANTA Flash CLIA achieving diagnostic performance equivalent to in-house ELISAs were 40 CU for moderate and 80 CU for high levels for aCL and anti-β2GPI IgG and IgM. The assays showed good qualitative agreement, ranging from 76.10 to 91.19 %. When considering in-house ELISA results, 14 out of 80 (17.5 %) patients did not fulfill the new ACR/EULAR laboratory classification criteria, while 27 out of 80 (33.8 %) did not when considering QUANTA Flash CLIA results.

CONCLUSIONS

We determined moderate and high thresholds for aCL and anti-β2GPI IgG and IgM detected with QUANTA Flash CLIA, aligning with long-established in-house ELISA thresholds. These thresholds are crucial for seamlessly integrating of the new 2023 ACR/EULAR classification criteria into future observational clinical studies and trials.

Effect of COVID-19 inactivated vaccine on peripheral blood anti-β2-GPI antibody and outcomes in vitro fertilization-embryo transplantation

Corona Virus Disease 2019 (COVID-19) is an acute respiratory infection and a global public health event. The level of aβ2GPI is significantly up-regulated in COVID-19 patients. The impact of inactivated vaccination against COVID-19 on aβ2GPI and in vitro fertilization and embryo transfer (IVF-ET) remains unknown amidst the universal administration of COVID-19 vaccines. We conducted a retrospective study to assess the impact of COVID-19 inactivated vaccination on aβ2GPI levels and its effect on superovulation and pregnancy outcomes. We found aβ2GPI level is significantly up-regulated after vaccination. There was no statistical difference in mature egg rate, 2PN fertilization rate, day 3 high-quality embryo rate, blastocyst formation rate, embryo implantation rate and miscarriage rate between the vaccine group and control group. Our findings showed vaccination with COVID-19 inactivated vaccine can elevate the level of aβ2GPI in peripheral blood but have no effect on the outcomes of controlled ovarian hyperstimulation and pregnancy in IVF-ET.

Obstetric anti-phospholipid syndrome: from pathogenesis to treatment

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by clinical manifestations such as thrombosis and obstetric complications with documented persistence of antiphospholipid antibodies (aPLs). Recent studies have revealed that the cause of aPL-related obstetric complications is dysfunction of placental trophoblasts and inflammation of the maternal-fetal interface induced by aPLs, not thrombosis. Although aPLs are associated with recurrence of serious complications during pregnancy, appropriate combination therapy with heparin and low-dose aspirin can improve the course of 70-80% of subsequent pregnancies. Preconception counseling and patient-tailored treatment are fundamental to improving maternal and fetal outcomes. Non-anticoagulant treatments such as hydroxychloroquine and statins are being developed for cases refractory to conventional treatment. Risk factors for thrombosis after pregnancy complications were identified based on the analysis of large databases of obstetric APS.

Prediction of Adverse Pregnancy Outcomes in Women with Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic, autoimmune disease associated with major obstetrical complications such as gestational loss, preterm delivery, fetal growth restriction (FGR) and preeclampsia. Published literature is not consensual regarding the main risk factors for each of these outcomes. Our goal with this study was to determine the most important predictors for each of the main adverse pregnancy outcomes in this population. We conducted a retrospective cohort study of unifetal pregnancies of women with the diagnosis of SLE followed in our unit between January 1994 and December 2016. We excluded elective terminations of pregnancy and cases lost to follow-up and we analyzed 157 pregnancies (128 women). Multiple logistic regression models for the outcomes gestational loss, preterm delivery, fetal growth restriction, and preeclampsia were built. Two-sided p-values of < 0.05 were used to determine statistical significance, and two-sided confidence intervals of 95% are reported. In our cohort, the main risk factors for gestational loss were maternal age and the presence of antiphospholipid antibodies. Lupic nephritis was predictive of a preterm delivery and preeclampsia. Renal involvement and lupus flares during pregnancy were risk factors for FGR. Overall, the main risk factor for an adverse pregnancy outcome were lupus flares during pregnancy. Despite optimal pregnancy monitoring, women with SLE are still at risk for adverse pregnancy outcomes. Risk stratification for each of these outcomes is crucial for an effective counselling and tailored monitoring.

EUREKA algorithm predicts obstetric risk and response to treatment in women with different subsets of anti-phospholipid antibodies

OBJECTIVES

aPL, the serum biomarkers of APS, are the most common acquired causes of pregnancy morbidity (PM). This study investigates the impact of aPL positivity fulfilling classification criteria ('criteria aPL') and at titres lower than thresholds considered by classification criteria ('low-titre aPL') on PM and assesses the effectiveness of low-dose aspirin (LDASA), low molecular weight heparin (LMWH) and HCQ in reducing the probability of PM (PPM).

METHODS

Longitudinal data on 847 pregnancies in 155 women with persistent aPL at any titre and 226 women with autoimmune diseases and negative aPL were retrospectively collected. A generalized estimating equations model for repeated measures was applied to quantify PPM under different clinical situations.

RESULTS

EUREKA is a novel algorithm that accurately predicts the risk of aPL-associated PM by considering aPL titres and profiles. aPL significantly impact PPM when at low titres and when fulfilling classification criteria. PPM was further stratified upon the aPL tests: aCL IgG/IgM and anti-β2-glycoprotein I (β2GPI) IgM, alone or combined, do not affect the basal risks of PPM, an increase occurs in case of positive LA or anti-β2GPI IgG. LDASA significantly affects PPM exclusively in women with low-titre aPL without anti-β2GPI IgG. The LDASA + LMWH combination significantly reduces PPM in all women with low-titre aPL and women with criteria aPL, except those carrying LA and anti-β2GPI IgG. In this group, the addition of HCQ further reduces PPM, although not significantly.

CONCLUSION

EUREKA allows a tailored therapeutic approach, impacting everyday clinical management of aPL-positive pregnant women.

An in vitro model to mimic the thrombotic occlusion of small vessels in catastrophic antiphospholipid syndrome (CAPS)

Platelet activation and decrease in platelet count characterize the development of the most feared form of antiphospholipid syndrome (APS), i.e. catastrophic APS (CAPS). We aimed to assess if immuno-affinity purified anti-β2-glycoprotein I (aβ2GPI) antibodies enhance platelet activation inducing a significant flow obstruction in a platelet function analyzer (PFA). Affinity purified aβ2GPI antibodies were obtained from 13 triple positive patients with a strong lupus anticoagulant (LA) and high titers of IgG anticardiolipin antibodies (aCL) and IgG aβ2GPI. Platelet activation stimulated by adenosine diphosphate (ADP) in the presence or absence of aβ2GPI was measured by the expression of P-selectin on platelet surface using flow cytometry. P-selectin expression remained close to baseline when normal whole blood was incubated with aβ2GPI alone. When stimulated using aβ2GPI combined with ADP, P-selectin expression (28.42 ± 5.15% vs. 20.98 ± 3.94%, p = 0.0076) was significantly higher than ADP alone. Closure time of normal whole blood passed through the PFA was significantly shorter using affinity purified aβ2GPI than control IgG both in Col/ADP (160.1 ± 62.1 s vs. 218.6 ± 43.8 s; p = 0.021) and Col/EPI cartridges (149.5 ± 26.7 s vs. 186.9 ± 45.5 s; p = 0.030). Thus, platelet activation is enhanced by aβ2GPI antibodies with a consequent premature closure in a PFA, possibly resembling that in microcirculation in patients with CAPS.

Triple Antiphospholipid (aPL) Antibodies Positivity Is Associated With Pregnancy Complications in aPL Carriers: A Multicenter Study on 62 Pregnancies

Objective: Antiphospholipid antibodies (aPL) are risk factors for thrombosis and adverse pregnancy outcomes (APO). The management of the so called “aPL carriers” (subjects with aPL positivity without the clinical criteria manifestations of APS) is still undefined. This study aims at retrospectively evaluating the outcomes and the factors associated with APO and maternal complications in 62 pregnant aPL carriers.

Methods: Medical records of pregnant women regularly attending the Pregnancy Clinic of 3 Rheumatology centers from January 1994 to December 2015 were retrospectively evaluated. Patients with concomitant autoimmune diseases or other causes of pregnancy complications were excluded.

Results: An aPL-related event was recorded in 8 out of 62 patients (12.9%) during pregnancy: 2 thrombosis and 6 APO. At univariate analysis, factors associated with pregnancy complications were acquired risk factors (p:0.008), non-criteria aPL manifestations (p:0.024), lupus-like manifestations (p:0.013), and triple positive aPL profile (p:0.001). At multivariate analysis, only the association with a triple aPL profile was confirmed (p:0.01, OR 21.3, CI 95% 1.84–247). Patients with triple aPL positivity had a higher rate of pregnancy complications, despite they were more frequently receiving combined treatment of low dose aspirin (LDA) and low molecular weight heparin (LMWH) at prophylactic dose.

Conclusion: This study highlights the importance of risk stratification in pregnant aPL carriers, in terms of both immunologic and non-immunologic features. Combination treatment with LDA and LMWH did not prevent APO in some cases, especially in carriers of triple aPL positivity. Triple positive aPL carriers may deserve additional therapeutic strategies during pregnancy.

The clinical value of assays detecting antibodies against domain I of β2-glycoprotein I in the antiphospholipid syndrome

As the clinical symptoms of the antiphospholipid syndrome (APS) frequently occur irrespective of the syndrome, diagnosis predominantly depends on the laboratory assays measuring the level or function of antiphospholipid antibodies (aPLs). β2-glycoprotein I (β2GPI) is increasingly accepted as the most important target of aPLs. Anti-β2GPI antibodies constitute a heterogeneous population, but current in vivo and in vitro evidence show that especially the first domain (DI) of β2GPI contains an important pathogenic epitope. This epitope containing Glycine40-Arginine43 (G40-R43) has proven to be cryptic and only exposed when β2GPI is in its open conformation. A previous study demonstrated a highly variable exposure of the cryptic epitope in commercial anti-β2GPI assays, with implications on correct patient classification. Unexpectedly, recent unpublished data revealed impaired exposure of the pathogenic epitope in the commercially available anti-DI chemiluminescence immunoassay (CIA) assay detecting specific antibodies directed to DI. In this review we summarize the laboratory and clinical performance characteristics of the different anti-DI assays in published data and conclude with inconsistent results for both the correlation of anti-DI antibodies with clinical symptoms and the added value of anti-DI antibodies in the classification criteria of APS. Additionally, we hypothesize on possible explanations for the observed discrepancies. Finally, we highly advise manufacturers to use normal pooled plasma spiked with the monoclonal anti-DI antibodies to verify correct exposure of the cryptic epitope.

The Clinical Performance of a New Chemiluminescent Immunoassay in Measuring Anti-β2 Glycoprotein 1 and Anti-Cardiolipin Antibodies

BACKGROUND Laboratory criterion is needed for the classification of antiphospholipid syndrome (APS), which contain anticardiolipin antibodies (aCL) and anti-β2-glycoprotein 1 antibodies (aβ2GP1). They are commonly identified by enzyme-linked immunosorbent assay (ELISA), but lack standardized kits, resulting in substantial variations in the antibody positivity between different laboratories. The emergence of chemiluminescence automated -BIO-FLASH may improve the situation. MATERIAL AND METHODS We selected 185 patients with APS, systemic lupus erythematosus (SLE), infertility, connective tissue disease (CTD), and other conditions in Peking University Third Hospital. We tested the aCL and aβ2GP1 levels by EUROIMMUN ELISA and 105 patients had at least one positive result for aCL and aβ2GP1, while the others had negative results. We retested them by chemiluminescence assay (CIA) and analyzed the result and compared the coincidence rate. The IgM levels were retested by AESKU ELISA. Data were analyzed using SPSS. RESULTS Our result suggested that CIA had good performance for IgG isotype of aCL and aβ2GP1 in the coincidence rate. The positive coincidence rate of aCL IgM between CIA and EUROIMMUN ELISA was only 41.67%, but two ELISA kits showed good coincidence, CIA and AESKU ELISA had an obviously higher positive rate. CIA and AESKU had a higher coincidence than that of AESKU and EUROIMMUN in aβ2GP1-IgM. CONCLUSIONS The new automated CIA BIO-FLASH is suitable for detecting aCL and aβ2GP1 antibodies, especially IgG isotype, which may provide an alternative to time-consuming conventional ELISA method.

Clinical value of anti-domain I-β2Glycoprotein 1 antibodies in antiphospholipid antibody carriers. A single centre, prospective observational follow-up study

BACKGROUND

There seems to be a clear correlation between antibodies against domain I (anti-DI) of β2Glycoprotein I and severe clinical profiles in antiphospholipid syndrome (APS) patients. We investigated the clinical significance of anti-DI antibodies in a cohort of aPL carriers.

METHODS

One hundred and five carriers persistently positive for IgG anti-β2Glycoprotein 1 antibodies (a-β2GPI) and/or IgG anticardiolipin (aCL) and/or lupus anticoagulants (LAC) were tested for the presence of anti-DI antibodies using the QUANTA Flash® Beta2GPI-Domain I chemiluminescence immunoassay.

RESULTS

Anti-DI antibodies were detected in 44 aPL carriers (41.9%) and they were significantly associated to triple aPL positivity (LAC plus IgG a-β2GPI plus IgG aCL antibodies). Isolated LAC and a-β2GPI antibodies were significantly associated to anti-DI negative aPL carriers. During a 82.2 month mean follow-up, ten aPL carriers (9.5%) developed a first thrombotic event so becoming APS patients. Anti-DI antibodies, triple aPL positivity, thromboembolic risk factors and autoimmune disorders significantly prevailed in carriers becoming APS. Logistic regression analysis showed that anti-DI positivity was an independent risk factor for thrombosis.

CONCLUSIONS

Anti-DI antibody positivity can be considered a new risk factor predictive of the first thrombotic event in aPL carriers, instead, negative anti-DI may be useful to identify low-risk aPL carriers.

Long-term use of hydroxychloroquine reduces antiphospholipid antibodies levels in patients with primary antiphospholipid syndrome

Hydroxychloroquine (HCQ) was suggested to play a role in lowering antiphospholipid antibody titers and preventing thrombotic recurrences in patients with systemic lupus erythematosus, but few data are available in patients with primary antiphospholipid syndrome (PAPS). In this retrospective, propensity score-matched cohort study, we evaluated the impact of HCQ on aPL titers and the incidence of thrombotic events in 57 exposed patients compared to 57 not exposed patients. These were matched for sex/type of disease onset/follow-up duration, age at the beginning of the follow-up ±10 years and initial date of the follow-up ±5 years. At baseline, no significant differences in demographical, clinical and serological features were observed between the two groups except for positive anti-extractable nuclear antigen antibodies (21 % in HCQ exposed vs 0 % in HCQ not exposed, P = 0.001). Both the levels of IgG anti-cardiolipin and IgG/IgM anti-β2-glycoprotein I (anti-β2GPI) were significantly reduced at end of follow-up compared to the baseline in HCQ-exposed patients, while there were no differences in the other group. Moreover, anti-β2GPI IgG titers were significantly decreased when the end of follow-up was compared between the two groups (P < 0.002). Among patients with a history of thrombosis, the annual incidence of recurrence was 1.16 % in HCQ exposed and 1.71 % in not exposed patients, with a significant reduction in the incidence of arterial events (0 vs 1.14 %). This study shows a strong reduction in aPL titers together with an apparent decrease in the incidence of arterial thrombosis recurrence in PAPS patients treated with HCQ.

Beyond thrombosis: Anti-β2GPI domain 1 antibodies identify late pregnancy morbidity in anti-phospholipid syndrome

Antibodies against β2 glycoprotein I (anti-β2GPI) have been identified as the main pathogenic autoantibody subset in anti-phospholipid syndrome (APS); the most relevant epitope is a cryptic and conformation-dependent structure on β2GPI domain (D) 1. Anti-β2GPI domain profiling has been investigated in thrombotic APS, leading to the identification of antibodies targeting D1 as the main subpopulation. In contrast, scarce attention has been paid to obstetric APS, hence this study aimed at characterizing the domain reactivity with regards to pregnancy morbidity (PM). To this end, 135 women with persistently positive, medium/high titre anti-β2GPI IgG, without any associated systemic autoimmune diseases and at least one previous pregnancy were included: 27 asymptomatic carriers; 53 women with obstetric APS; 20 women with thrombotic APS; and 35 women with both thrombotic and obstetric complications. Anti-D1 and anti-D4/5 antibodies were tested using a chemiluminescent immunoassay and a research ELISA assay, respectively (QUANTA Flash^® β2GPI Domain 1 IgG and QUANTA Lite^® β2GPI D4/5 IgG, Inova Diagnostics). Positivity for anti-D1 antibodies, but not anti-D4/5 antibodies, was differently distributed across the 4 subgroups of patients (p < 0.0001) and significantly correlated with thrombosis (χ2 = 17.28, p < 0.0001) and PM (χ2 = 4.28, p = 0.039). Patients with triple positivity for anti-phospholipid antibodies displayed higher anti-D1 titres and lower anti-D4/5 titres compared to women with one or two positive tests (p < 0.0001 and p = 0.005, respectively). Reactivity against D1 was identified as a predictor for PM (OR 2.4, 95% confidence interval [CI] 1.2-5.0, p = 0.017); in particular, anti-D1 antibodies were predictive of late PM, conveying an odds ratio of 7.3 (95% CI 2.1-25.5, p = 0.022). Positivity for anti-D1 antibodies was not associated with early pregnancy loss. Anti-D4/5 antibodies were not associated with clinical APS manifestations. As a whole, our data suggest that anti-D1 antibodies are significantly associated not only with thrombosis, but also with late PM, while positive anti-D4/5 antibodies are not predictive of thrombosis or PM.

Phospholipid inhibitors

The antiphospholipid syndrome (APS) is defined by the association of arterial and/or venous thrombosis and/or pregnancy complications with the presence of at least one among the main antiphospholipid antibodies (aPL) (i. e., Lupus anticoagulants, LA, IgG and/ or IgM anticardiolipin antibodies, aCL, IgG and/or IgM antiβ2-glycoprotein I antibodies, aβ2-GPI). Several clinical studies have consistently reported that LA is a stronger risk factor for both arterial and venous thrombosis compared to aCL and aβ2-GPI. In particular, LA activity dependent on the first domain of β2-GPI and triple aPL positivity are associated with the risk of thrombosis and obstetrical complications.

Asymptomatic aPL-positive subjects do not require primary thromboprophylaxis. Venous thromboembolism is the most common initial clinical manifestation of APS. To prevent its recurrence indefinite anticoagulation is recommended. Long duration treatment with warfarin or aspirin is used after a first cerebral arterial thrombosis. Low molecular weight heparin (LMWH) with or without aspirin is recommended to reduce the rate of obstetrical complications of APS pregnant women.

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.

Antiphospholipid syndrome and recurrent miscarriage: A systematic review and meta-analysis

Antiphospholipid syndrome (APS) is an autoimmune condition that is associated with thrombosis and morbidity in pregnancy. The exact mechanisms by which these associations occur appear to be heterogeneous and are not yet well understood. The aim of this study was to identify and analyze publications in recent years to better understand the diagnosis and its contribution to monitoring APS among women with recurrent miscarriage (RM). This systematic review and meta-analysis was conducted using the PubMed and Web of Knowledge databases, with articles published between 2010 and 2014, according to the PRISMA statement. Of the 85 identified studies, nine were selected. Most of the studies reported an association between recurrent miscarriage and specific antiphospholipid antibodies, as anticardiolipin antibodies (aCL), lupus anticoagulant (LA), anti-β2-glycoprotein I antibodies (aβ2GPI) and antiphosphatidylserine (aPS), which showed a relationship with RM. The main result of the meta-analysis revealed association between antiphospholipid antibodies (aPLs) and/or APS compared to the patients with RM (OR: 0.279; 95% CI: 0.212-0.366) and APS cases compared to the patients with RM (OR: 0.083; 95% CI: 0.036-0.189). High heterogeneity among these studies (I²=100.0%, p <0.001) was observed. In addition, there was no significant publication bias across studies according to Begg's test (p=0.230), although Egger's test (p=0.037) suggests significant publication bias. The funnel plot was slightly asymmetrical. Systematic review and meta-analysis demonstrated a positive association between antiphospholipid antibodies and/or antiphospholipid syndrome in patients with recurrent miscarriage.

Longterm Outcome of Patients with Primary Antiphospholipid Syndrome: A Retrospective Multicenter Study

OBJECTIVE

To assess the longterm frequency of thrombotic recurrences, obstetrical complications, organ damage, severe comorbidities, and evolution toward connective tissue disease (CTD) in primary antiphospholipid syndrome (PAPS).

METHODS

Medical records of patients with PAPS followed in 6 centers for ≥ 15 years were retrospectively reviewed.

RESULTS

One hundred fifteen patients were studied: 88% women, followed between 1983 and 2014 with a mean (± SD) age at diagnosis of 33 (± 10) years. During a median followup of 18 years (range 15-30), 50 patients (44%) had at least a thrombotic event for a total of 75 events and an annual incidence of 3.5%. Thromboses were more frequent in patients with previous thrombotic history (p = 0.002). A catastrophic antiphospholipid syndrome occurred in 6 patients (5%). The use of oral anticoagulants in patients with thrombotic onset did not appear to be protective against recurrences (p = 0.26). Fifty-two women had 87 pregnancies, successful in 78%. Twenty-nine percent of patients accrued functional damage. Damage was significantly associated with a thrombotic history (p = 0.004) and with arterial events (p < 0.001), especially stroke, but not with demographics, serology, or treatment. Twenty-four major bleeding episodes were recorded in 18 patients, all receiving anticoagulants. Severe infections affected 6 patients (5%), with 1 fatality. A solid cancer was diagnosed in 8 patients (7%). Altogether, 16 patients (14%) developed an autoimmune disease and 13 (11%) a full-blown picture of CTD.

CONCLUSION

Despite therapy, a high proportion of patients experienced new thrombotic events and organ damage, while evolution toward CTD was infrequent.

Antiphosphatidylserine/prothrombin antibodies as biomarkers to identify severe primary antiphospholipid syndrome

Background:

Anti-phosphatidylserine/prothrombin (aPS/PT) antibodies have begun to be considered potentional biomarkers for antiphospholipid syndrome (APS). This cohort study investigate the role of aPS/PT antibodies as a risk factor for severe APS by evaluating the association between those antibodies and clinical/laboratory profiles of APS.

Methods:

Plasma/serum samples from 197 APS patients, 100 healthy subjects and 106 patients with autoimmune diseases were collected. IgG/IgM aPS/PT antibodies were assayed using commercial ELISA kit.

Results:

Prevalences of IgG and IgM aPS/PT (p<0.0001 and p=0.0009, respectively) and their titres (p<0.0001 and p=0.0002, respectively) were significantly higher in thrombosis/pregnancy group with respect to pregnancy morbidity alone. Prevalences of IgG and IgM aPS/PT (p<0.0001 and p=0.0004, respectively) and their mean levels (p=0.0001 for both) were significantly higher in the prematurity linked to life-threatening obstetric complications group with respect to miscarriage group. There was a significant relationship between IgG and IgM aPS/PT (p=0.001 and p=0.0002) and their mean levels were higher (p=0.0004 and p=0.0002, respectively) in the thrombotic microangiopathy group, considered a milestone manifestation of catastrophic APS. The relationship between IgG and IgM aPS/PT was significant and mean levels were higher in triple positive antiphospholipid antibody patients than in double and single positivity ones (p<0.0001 for all).

Conclusions:

APS/PT antibodies were associated to severe thrombosis, severe pregnancy complications inducing prematurity, and vascular microangiopathy, all generally associated to high risk APS forms requiring strong therapy.

Long-term neurodevelopmental outcome of children born to prospectively followed pregnancies of women with systemic lupus erythematosus and/or antiphospholipid syndrome

Background

Systemic lupus erythematosus (SLE) and antiphospholipid antibody syndrome (APS) are autoimmune diseases that affect women of childbearing age. Maternal IgG antiphospholipid antibodies (aPL) can cross the placenta during pregnancy and theoretically reach the fetal brain. Some studies showed an increased number of learning disabilities in these children.

Objectives

To evaluate the long-term neurodevelopmental outcome of 40 children (median age 7.4 years) born to mothers with SLE and/or APS carrying positive IgG aPL during the third trimester of pregnancy.

Methods

Children were checked for neurological physical exam and intellectual/cognitive functioning by the Wechsler scale for corrected age. We submitted to the mothers the Child Behavior CheckList (CBCL) and a homemade set of questions created by pediatric neurologists.

Results

In all children neurological physical exam and intelligence levels were found to be normal. A cognitive impairment or a discrepant cognitive profile was found in 3 (7%) and 11 (28%) children, respectively. Learning disabilities were diagnosed in 3 children (19% of school-age children), all born to mothers with triple aPL positivity. A history of epilepsy was shown in four children (10%). Conclusions: Children born to women with SLE and/or APS may need a long-term follow-up focusing on milestones of neurodevelopment in order to detect and correct any alteration as early as possible.

Variability in Anticardiolipin Antibody Detection: Role of Nonspecific IgG Binding and Different Microtiter Plates

There are many studies that are available on the Internet that attempt to standardize the assay for anticardiolipin antibody evaluation because of the variability of results. The aim of this study was to evaluate simultaneously the role of different microplates and the importance of sample nonspecific binding in determining different results in anticardiolipin antibody detection. Sera from 8 patients with raised levels of IgG anticardiolipin antibodies and 10 control sera were assayed by enzyme-linked immunosorbent assay in the presence (specific binding) or in the absence of cardiolipin (sample blank) with four different microplates, that is, NUNC PolySorp, FALCON ProBIND, Greiner 655061 (high binding), and Greiner 655001 (medium binding). Results were expressed as optical densities or net-optical densities (following sample blank subtraction) as well as international IgG anticardiolipin units (GPL) or net-GPL. A wide interplate variability of optical densities was found. When results were expressed as GPL, significant differences were only found between Greiner 655061, FALCON ProBIND, and NUNC PolySorp ( P < .05 and P < .001, respectively) whereas differences were not statistically significant if interplate variability was analyzed as net-GPL. Results expressed as categorical variables (ie, positive/negative, according to a GPL cut-off and net-GPL cut-off, obtained with sera from 100 apparently healthy blood donors) showed a good or excellent Cohen's κ coefficient of concordance among plates when positivity was evaluated on net-GPL. Our data strongly suggest that quantification and subtraction of sample blank may improve both interlaboratory agreement and reliability of anticardiolipin assay and minimize false-positive results.

Clinical characterization of antiphospholipid syndrome by detection of IgG antibodies against β2 -glycoprotein i domain 1 and domain 4/5: ratio of anti-domain 1 to anti-domain 4/5 as a useful new biomarker for antiphospholipid syndrome

OBJECTIVE

It has been suggested that only antibodies against domain 1 (D1) of β2 -glycoprotein I (β2 GPI) are pathogenic and diagnostic. The role of antibodies against other β2 GPI domains is still debated. This study was undertaken to evaluate the clinical relevance of domain specificity profiling of anti-β2 GPI IgG antibodies in antiphospholipid syndrome (APS) patients and in control groups of patients with systemic autoimmune rheumatic diseases and in asymptomatic antiphospholipid antibody (aPL) carriers.

METHODS

We evaluated 159 subjects with persistently positive, medium or high-titer anti-β2 GPI IgG, including 56 patients with thrombotic (obstetric or nonobstetric) primary APS, 31 women with obstetric primary APS, 42 aPL-positive patients with systemic autoimmune rheumatic diseases, and 30 asymptomatic aPL carriers. One hundred healthy donors were included. Anti-β2 GPI D1 and D4/5 IgG were tested on research enzyme-linked immunosorbent assays containing recombinant β2 GPI domains.

RESULTS

As compared to other groups, aPL carriers displayed higher frequency/titer of anti-D4/5 IgG. Unlike anti-D4/5, anti-D1 IgG antibodies were more frequent and at higher titer in triple than in single or double aPL-positive subjects. An anti-D1 to anti-D4/5 ratio of ≥1.5 was predictive of systemic autoimmunity (odds ratio 3.25 [95% confidence interval 1.45-7.49], P = 0.005). Neither anti-D1 nor anti-D4/5 antibodies were associated with APS clinical criteria.

CONCLUSION

Anti-D1 IgG is the preferential specificity not only in vascular and obstetric primary APS, but also in patients with systemic autoimmune rheumatic disease with no clinical features of APS. Conversely, aPL carriers do not have a polarized profile toward D1. Combined testing for anti-β2 GPI IgG with different domain specificity allows a more accurate aPL profiling, with polarization toward anti-D1 IgG as a possible fingerprint of systemic autoimmunity.

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.

Intractable headaches, ischemic stroke, and seizures are linked to the presence of anti-β2GPI antibodies in patients with systemic lupus erythematosus

Background

Neuropsychiatric systemic lupus erythematosus (NPSLE) is a common and potentially fatal manifestation of SLE. Antiphospholipid antibodies (aPL) such as lupus anticoagulant (LA), anticardiolipin (aCL) and antibodies to β2glycoprotein I (anti-β2GPI), the most important aPL antigen, are thought to play a role in some forms of NPSLE. As of yet, their specific roles in NPSLE manifestations remain to be elucidated.

Methodology/Principal Findings

57 SLE patients (53 women) were assessed for LA, aCL and anti-β₂GPI twice, to determine persistent positivity. All patients were examined by neurology and psychiatry specialists. 69 healthy subjects were assessed as controls. NPSLE was diagnosed in 74% of patients. Headaches were the most prevalent manifestation of NPSLE (39%), followed by cerebrovascular disease (CVD) (23%), depressive disorders (19.0%), and seizures (14%). NPSLE and non-NPSLE patients showed comparable SLE activity and corticosteroid use. In 65% of patients neuropsychiatric manifestations preceded SLE diagnosis. aPL profiles of NPSLE patients and non-NPSLE patients were similar. Headaches and ischemic stroke were independently associated with anti-β₂GPI-IgM (OR=5.6; p<0.05), and seizures were linked to anti-β₂GPI-IgG (OR=11.3; p=0.01).

Conclusions

In SLE patients, neuropsychiatric manifestations occur frequently and early, often before the disease is diagnosed. Autoantibodies to β2GPI are linked to non-specific headaches, ischemic stroke and seizures, and show a better predictive value than aCL and LA. These findings may help to improve the diagnosis of NPSLE and should prompt further studies to characterize the role of anti-β2GPI in the pathogenesis of this condition.

Antiphospholipid antibody testing and standardization

The laboratory criteria that define patients with antiphospholipid syndrome (APS) include lupus anticoagulant (LAC), anticardiolipin antibodies and anti-β2 glycoprotein I antibodies (aβ2GPI). All assays show methodological shortcomings and the combination of the three tests, each with different sensitivity and specificity, and hence, differences in clinical utility make the laboratory diagnosis of APS challenging. Consensus guidelines and proposals for antiphospholipid antibodies (aPL) testing have been published in the last 20 years and have led to a substantial improvement. Despite efforts so far, standardization is not reached yet, but progress has been made. On-going efforts to reduce the interlaboratory/interassay variations remain important; even an absolute standardization cannot be feasibly achieved. Taking into account the methodological shortcomings of the means we have available, more detailed guidelines may help in adequate performance of aPL testing. This review will focus on the efforts and achievements in standardization and on the weaknesses and strengths of the current available laboratory methods.

Refinement of the cutoff values of the HemosIL AcuStar assay for the detection of anticardiolipin and anti-beta2 glycoprotein-1 antibodies

BACKGROUND

The HemosIL AcuStar antiphospholipid assay (Instrumentation Laboratory, Bedford, MA, USA) is a fully automated assay using chemiluminescent technology for the detection of anticardiolipin and anti-beta2 glycoprotein-1 antibodies. This assay showed excellent agreement between results of different laboratories. The cutoff values to define positivity were calculated in 250 healthy blood bank donors but were associated with large confidence intervals (CIs).

OBJECTIVE

The objective of this study was to more precisely determine the cutoff values of the HemosIL AcuStar antiphospholipid assay by increasing the number of healthy blood bank donors through a multicenter study and by applying a normalization procedure of the distribution of each antibody.

METHODS

Five laboratories participated to this study, allowing the inclusion of 626 samples. We used a Box-Cox power transformation method to normalize the distribution and calculate the 99th percentile and the corresponding 95%CI for each antibody.

RESULTS

The revised cutoff values were overall lower than those initially calculated with more stringent CIs and yielded a 4.2% increase in sensitivity with a 2.7% decrease in specificity regarding thrombotic events or obstetric complications.

CONCLUSIONS

We provide refined cutoff values for the detection of anticardiolipin and anti-beta2 glycoprotein-1 antibodies with the HemosIL AcuStar Antiphospholipid assay that should be preferred for routine use.

Treatment strategies and pregnancy outcomes in antiphospholipid syndrome patients with thrombosis and triple antiphospholipid positivity. A European multicentre retrospective study

Previous thrombosis, diagnosis of systemic lupus erythematosus (SLE) and triple antiphospholipid (aPL) antibody positivity have recently been found to be independent factors associated to pregnancy failure during conventional therapy in women with antiphospholipid syndrome (APS). This study aimed to assess the effect of various treatment strategies on pregnancy outcomes in women with APS and the risk factors for pregnancy failure. One hundred ninety-six pregnancies of 156 patients diagnosed with APS were analysed: 118 (60.2%) of these had previous thrombosis, 81 (41.3%) were diagnosed with SLE, and 107 (54.6%) had triple aPL positivity. One hundred seventy-five (89.3%) were treated with conventional therapies (low-dose aspirin [LDA] or prophylactic doses of heparin + LDA or therapeutic doses of heparin + LDA), while 21 (10.7%) were prescribed other treatments in addition to conventional therapy. The pregnancies were classified into seven risk profiles depending on the patients' risk factors - thrombosis, SLE, and triple aPL positivity - and their single, double or triple combinations. It was possible to find significant difference in outcomes correlated to treatments only in the thrombosis plus triple aPL positivity subset, and logistic regression analysis showed that additional treatments were the only independent factor associated to a favourable pregnancy outcome (odds ratio=9.7, 95% confidence interval=1.1-88.9, p-value<0.05). On the basis of this retrospective study, we found that APS pregnant patients with thrombosis and triple aPL positivity treated with additional therapy had a significant higher live-birth rate with respect to those receiving conventional therapy alone.

14th International Congress on Antiphospholipid Antibodies Task Force. Report on antiphospholipid syndrome laboratory diagnostics and trends

Current classification criteria for definite Antiphospholipid Syndrome (APS) require the use of three laboratory assays to detect antiphospholipid antibodies (aCL, anti-β2GPI and LA) in the presence of at least one of the two major clinical manifestations (i.e. thrombosis or pregnancy morbidity) of the syndrome. However, several other autoantibodies shown to be directed to other proteins or their complex with phospholipids have been proposed to be relevant to APS but their clinical utility and their diagnostic value remains elusive. This report summarizes the findings, conclusions and recommendations of the "APS Task Force 3-Laboratory Diagnostics and Trends" meeting that took place during the 14th International Congress on Antiphospholipid Antibodies (APLA 2013, September 18-21, Rio de Janeiro, RJ, Brazil).

A new Eu(3+)-labeled method for anticardiolipin antibody IgM

BACKGROUND

The anticardiolipin antibodies (aCL) test has become a laboratory standard for the clinical diagnosis of antiphospholipid syndrome (APS). To better the quantitative detection of aCL-IgM so as to classify patients correctly and timely as APS positive, we established herein a new immunoassay based on a time-resolved fluoroimmunoassay (TRFIA).

METHODS

The complex of cardiolipin plus bovine anti-β2 glycoprotein-I was used as antigen fixed on microtiter plates to detect serum aCL-IgM, and Eu(3+) -labeled rabbit antihuman IgM was used as conjugate. The precision, sensitivity, specificity, coefficient of recovery, and stability of the assay were evaluated, and comparison with the traditional, classical enzyme-linked immunosorbent assay (ELISA) was also made.

RESULTS

The detection limit of the aCL-IgM TRFIA kit we established was 0.1 MPL U/ml, with a wider detectable range than commercial ELISA ones when a strong-positive specimen was diluted from 2,630.9 to 0.08 MPL U/ml. There was a good liner range within 0.16 to 2,630.9 MPL U/ml, whereas it was within 5.14 to 328.86 MPL U/ml when using three commercial ELISA ones. The average intra- and interassay variability was 3.19 and 3.70%, respectively. The mean recovery rate was 101.95%. The clinical diagnostic specificity was 98%. Additionally, the established assay kit presented good characteristics of stability and correlated well with the ELISA, and the correlation coefficient was 0.955.

CONCLUSION

The aCL-IgM TRFIA provides an approach to a more sensitive and reliable diagnosis of APS. Further validation of its use is required.

Multiple presence of prothrombotic risk factors in Croatian children with arterial ischemic stroke and transient ischemic attack

Aim

To determine the frequency of inherited and acquired prothrombotic risk factors in children with arterial ischemic stroke (AIS) and transient ischemic attacks (TIA) in Croatia.

Methods

We investigated 14 prothrombotic risk factors using blood samples from 124 children with AIS or TIA and 42 healthy children. Prothrombotic risk factors were classified into five groups: natural coagulation inhibitors (antithrombin, protein C, protein S), blood coagulation factors (FV Leiden and FII 20210), homocysteine, lipid and lipoprotein profile (lipoprotein (a), triglycerides, total, high- and low-density lipoprotein), and antiphospholipid antibodies (lupus anticoagulant, anticardiolipin, and antiphosphatidylserine antibodies).

Results

The most common prothrombotic risk factor was elevated lipoprotein (a), which was identified in about 31% of patients and in 24% of controls. Natural coagulation inhibitors were decreased in about 19% of patients, but not in controls. Pathological values of homocysteine, blood coagulation factor polymorphisms, and antiphospholipid antibodies were found in similar frequencies in all groups. Fourteen children with AIS and TIA (11.3%) and no children from the control group had three or more investigated risk factors.

Conclusion

The presence of multiple prothrombotic risk factors in children with cerebrovascular disorder suggests that a combination of risk factors rather than individual risk factors could contribute to cerebrovascular disorders in children.

Standardization of autoantibody testing: a paradigm for serology in rheumatic diseases

Autoantibody measurement is an excellent tool to confirm the diagnosis of rheumatic autoimmune diseases. Hence, reliability and harmonization of autoantibody testing are essential, but these issues are still a matter of debate. Intrinsic variability in analytes and reagents as well as heterogeneity of the techniques are the main reasons for discrepancies in inter-laboratory variations and reporting of test results. This lack of reliability might be responsible for wrong or missed diagnoses, as well as additional costs due to assay repetition, unnecessary use of confirmatory tests and/or consequent diagnostic investigations. To overcome such issues, the standardization of autoantibody testing requires efforts on all aspects of the assays, including the definition of the analyte, the pre-analytical stages, the calibration method and the reporting of results. As part of such efforts, the availability of suitable reference materials for calibration and quality control would enable the development of a reliable reference system. Strong-positive sera from patients have been used as reference materials in most of the autoantibody assays for rheumatic diseases; however, antigen-affinity-purified immunoglobulin fractions or in some cases reliable monoclonal antibody preparations offer more adequate tools for standardization. Systematic assessments of reference materials are currently underway, and preliminary results appear to be encouraging.

Primary adrenal insufficiency due to bilateral adrenal hemorrhage-adrenal infarction in the antiphospholipid syndrome: long-term outcome of 16 patients

CONTEXT

Primary adrenal insufficiency due to bilateral adrenal hemorrhage-adrenal infarction is a rare and life-threatening manifestation of the antiphospholipid syndrome (APLS). Data on the long-term outcome are scarce.

OBJECTIVE

The aims of the present study were to analyze the long-term outcome related to APLS per se and to characterize the course of adrenal involvement.

DESIGN

We conducted a retrospective study of patients with bilateral adrenal hemorrhage-adrenal infarction secondary to APLS seen in the Department of Internal Medicine of Pitié-Salpêtrière Hospital in Paris (France) between January 1990 and July 2010.

RESULTS

Three patients died during the acute phase related to APLS manifestations. Sixteen patients (7 males; 9 females) were followed up during a median period of 3.5 years (range 0.3-28.1 years). Three episodes of recurrent thrombosis were noted. One patient died from cerebral hemorrhage 3 months after the onset of adrenal insufficiency. Repeated Synacthen tests showed complete absence of response in 8 of the 10 patients assessed; cortisol and aldosterone increased appropriately in one patient and to some extent in another one. Dehydroepiandrosterone levels and 24-hour urinary epinephrine levels remained abnormally low in all evaluated patients. Adrenal imaging performed more than 1 year after the initial event revealed completely atrophic glands in 9 of 11 patients.

CONCLUSIONS

This particular subset of APLS patients who survive the acute phase has a rather favorable long-term outcome. Although adrenal dysfunction is generally irreversible, adrenocortical function may, at least partially, recover in rare cases. In this view, measurement of early morning cortisol during follow-up is indicated to detect these patients.

Confirmation of initial antiphospholipid antibody positivity depends on the antiphospholipid antibody profile

BACKGROUND

The revised classification criteria for the antiphospholipid syndrome state that antiphospholipid (aPL) antibodies (lupus anticoagulant [LAC] and/or anticardiolipin [aCL] and/or anti-β2 -glycoprotein I [aβ2 GPI] antibodies) should be detected on two or more occasions at least 12 weeks apart. Consequently, classification of patient risk and adequacy of treatment may be deferred by 3 months.

OBJECTIVES

In order to early classify patient risk, we evaluated whether aPL positivity confirmation is related to aPL antibody profiles.

PATIENTS AND METHODS

Consecutive patients referred to our center who were initially positive in one or more tests exploring the presence of aPL were tested after 3 months. During a 4-year period, 225 patients were initially positive in one or more tests, and 161 were available for confirmation after 3 months. Patients were classified as triple-positive (n = 54: LAC(+) , aCL(+) , aβ2 GPI(+) , same isotype), double-positive (n = 50: LAC(-) , aCL(+) , aβ2 GPI(+) , same isotype) and single-positive (n = 53: LAC or aCL or aβ2 GPI antibodies as the sole positive test).

RESULTS

Among subjects with triple positivity at initial testing, 98% (53 of 54) had their aPL profile confirmed after 12 weeks. The double-positive and single-positive groups had data confirmed in 42 of 50 (84%) and 23 of 57 (40%) subjects, respectively.

CONCLUSIONS

Our results show that high-risk subjects with triple-positive aPL profiles are identified early, at the time of the initial screening tests.

Platelet and endothelial activation in catastrophic and quiescent antiphospholipid syndrome

Antiphospholipid antibodies (aPL) seem to induce a prothrombotic state by activating endothelium and platelets, but no studies have evaluated systematically the effects of aPL from patients with the antiphospholipid syndrome (APS) in quiescent versus catastrophic phase. Our aims were to evaluate the in vitro effects on platelet activation of anti-β2 glycoprotein I (anti-β2GPI) antibodiesisolated from APS patientin either quiescent or catastrophic phase and to investigate ex vivo platelet and endothelial activation in patients with quiescent or catastrophic APS. Anti-β2GPI antibodies were isolated from plasma of a pregnant woman in two different stages of APS (quiescent and catastrophic, respectively). They were co-incubated with washed platelets from healthy controls that were then challenged with TRAP-6 (thrombin receptor activating peptide 6) and the expression of P- selectin (P-sel) on platelets was assessed by flow cytometry. Moreover, plasma samples from six patients with quiescent, four with catastrophic APS and 10 controls were assessed for several markers of platelet and endothelial activation. The results showed that purified anti-β2GPI antibodies co-incubated with platelets enhanced TRAP-6- induced platelet P-sel expression. Notably, anti-β2GPI antibodies isolated during the catastrophic phase enhanced platelet P-sel expression more than antibodies isolated from the same patient in the quiescent stage of disease. Moreover, APS patients had significantly higher plasma levels of soluble (s) Psel, sCD40 ligand, soluble vascular cell adhesion molecule 1 and monocyte chemoattractant protein 1 than control subjects. In addition, sP-sel and von Willebrand factor activity were significantly higher during catastrophic than in quiescent phase.

Treatment of 139 pregnancies in antiphospholipid-positive women not fulfilling criteria for antiphospholipid syndrome: a retrospective study

OBJECTIVE

The effect of low-dose aspirin (LDA) on pregnancy outcome in antiphospholipid (aPL)-positive women not fulfilling the criteria for antiphospholipid antibody syndrome (APS) was evaluated retrospectively.

METHODS

We evaluated 139 pregnancies of 114 aPL-positive women not fulfilling the Sydney classification criteria for definite APS (104 treated with LDA, 35 untreated). Inclusion criteria consisted of (1) any titer of aPL and no previous pregnancy or no pregnancy losses (defined as aPL carriers); (2) any titer of aPL and 1 or 2 pregnancy losses before the 10th gestational week. No women had previous thrombosis. The rate of pregnancy loss, gestational age at delivery, and birth weight percentile were compared in the treated and untreated patients. Associations between clinical and laboratory characteristics and pregnancy outcomes were investigated.

RESULTS

The rate of pregnancy loss was low in both treated and untreated groups (7.7% vs 2.9%, respectively). There were no statistically significant differences in the rate of pregnancy loss, gestational age at birth, or birth weight percentile in the treated and untreated groups. There were significant associations between gestational age at birth ≤ 34th week and positivity for lupus anticoagulant (p = 0.025) and anti-ß2-glycoprotein I IgG antibodies at titers > 99th (p = 0.016).

CONCLUSION

LDA treatment does not appear to improve pregnancy outcome in low-risk women not fulfilling the criteria for APS. Because antibody profile seems to influence pregnancy outcome, further studies of patients stratified according to their antibody profile are warranted.

Anticardiolipin antibody and anti-beta 2 glycoprotein I antibody assays

Antiphospholipid syndrome (APS) is an autoimmune disease and is a risk factor for a number of clinical manifestations; the classic presentations include fetal death or thrombosis (arterial or venous thromboembolism), in the presence of persistently increased titers of antiphospholipid (aPL) antibodies. The actual cause of APS is unknown but thought to be multifactorial. The disease is characterized by the presence of a heterogenous population of autoantibodies against phospholipid-binding proteins. APS presents either in isolation with no evidence of an underlying disease or in concert with an autoimmune disease such as systemic lupus erythematosus or rheumatoid arthritis. The wide diversity in clinical presentation often causes difficulty in identifying and treating patients and therefore a concise laboratory report containing interpretative comments is required to provide needed guidance to the clinician. For a diagnosis of APS to be made both clinical and laboratory classification criteria must be met. Laboratory testing to identify aPL antibodies includes lupus anticoagulant (liquid-based clotting assays) and immunological solid-phase assays (usually enzyme-linked immunosorbent assay formats) for IgG and/or IgM anticardiolipin (aCL) antibodies and anti-beta 2 glycoprotein I (β2-GPI) antibodies. Other autoantibodies, such as those directed against anionic phospholipids, can also be assayed; however they are not of clinical significance. Participation in a quality assurance program and an in-depth technical and clinical understanding of testing for aPL antibodies are required, as methods are limited by poor robustness, reproducibility, specificity, and standardization. Testing is further complicated by the lack of a "gold standard" laboratory test to diagnose or classify a patient as having APS. This chapter discusses the clinical and laboratory theoretical and technical aspects of aCL and anti-β2GPI antibody assays.

Circulating β2 glycoprotein I-IgG anti-β2 glycoprotein I immunocomplexes in patients with definite antiphospholipid syndrome

Beta2-glycoprotein I (β(2)GPI), a relevant antigen in Antiphospholipid Syndrome (APS), binds anionic macromolecules including heparin (Hep). A possible formation of ternary complexes between β(2)GPI, antibodies and Hep in APS is thus possible. The aim of this study was to evaluate Hep-β(2)GPI interaction in patients with APS. The affinity of Heps of different length, including unfractionated Hep (UFH), low-molecular weight Hep (enoxaparin) and pentasaccharide (fondaparinux), to human β(2)GPI was estimated by fluorescence spectroscopy, yielding dissociation constant (K(d)) values of 1.1, 24.0 and 89.4 µM, demonstrating that the longer UFH binds to β(2)GPI far more tightly than the shorter ones. Plasma and protein G-purified IgGs from eight patients with APS (i.e. five with thromboembolic disease and three with catastrophic APS), were fractionated by affinity chromatography using a Hep (UFH)-bound column, eluted with a linear NaCl gradient. For each chromatographic analysis, fractions were collected in the whole NaCl gradient and tested by ELISA for the presence of β(2)GPI and anti-β(2)GPI IgG. The results of Hep-affinity chromatography and ELISAs concurrently indicate that either β(2)GPI and anti-β(2)GPI IgG elute from the Hep column in the same chromatographic peak, at a retention time identical to that of the purified, isolated β(2)GPI, thus suggesting that circulating immunocomplexes containing β(2)GPI are present in patients with APS.

Detection of anticardiolipin antibody IgG by time-resolved fluoroimmunoassay

In an effort to improve the quantitative detection of anticardiolipin antibodies (aCL) IgG so as to classify patients correctly as antiphospholipid syndrome (APS) positive, we developed a new immunoassay based on a sandwich time-resolved fluoroimmunoassay (TRFIA) using the complex of cardiolipin plus bovine β(2)GPI as antigen and Eu(3+)-labeled rabbit antihuman IgG as conjugate. The precision, sensitivity, specificity, and stability of the assay were evaluated, and comparison with the classical ELISA was also made. The aCL IgG TRFIA kit we established had a wider detectable range than three commercial ELISA ones from different manufacturers when a specimen was diluted, with strong positive result from 1:12.5 to 1:204,800. The average intra-assay and inter-assay CVs detected by the aCL IgG TRFIA was 3.14 and 3.70 %, respectively. The sensitivity was 0.1 GPL U/ml, and the clinical diagnostic specificity was 98 %. The established assay kit also behaved better in stability than the commercial ELISA ones. Additionally, the immunoassay we established correlated well with the ELISA, and the correlation coefficient was 0.975. We thus conclude that the TRFIA we developed for aCL IgG detection gives promise to a more sensitive and reliable diagnosis of APS and has potential value for large-scale screening programs.

European Forum On Antiphospholipid Antibodies: brief history report and governance document

The European Forum on Antiphospholipid Antibodies was conceived as a multidisciplinary network of different specialists working in the fields of internal medicine, haematology, rheumatology, obstetrics and gynaecology, neurology, paediatrics, cardiology and immunology, among others, that share a common interest in these antibodies and antiphospholipid syndrome (APS). Centres with very good clinical practice in APS and with large cohorts of patients could join other centres with better research experience, thus allowing the study of basic patho-mechanisms in large series of patients. In addition, the specialists would be able to compare their cohorts of patients, which, being as they are recruited in very different fields of medicine, could enlighten the different aspects of APS. Finally, continuous comparison of patients’ data suggested that even the laboratory diagnostic procedures needed collaborative work in order to make reproducible results, at least of the classical tests – lupus anticoagulant (LA), anticardiolipin antibodies (aCLas) and anti β2-glycoprotein I antibodies (anti-β2GPIs) – and of the consequent clinical diagnosis in different centres. In this way, the wide exchange of information could also favour the introduction and evaluation of new tests.

Detection of antiphospholipid antibodies by automated chemiluminescence assay

The laboratory diagnosis of antiphospholipid antibody syndrome (APS) requires the demonstration of antiphospholipid antibodies (aPL) by lupus anticoagulant (LAC) measured through coagulation assays, anticardiolipin IgG or IgM antibodies (aCL) and/or anti-β2-glycoprotein I IgG or IgM antibodies (anti-β2-GPI), usually detected by ELISA. In this study we tested aCL by a new automated system using the chemiluminescence principle. Our results showed that, while almost all the sera from APS patients, positive for IgG aCL and anti-β2-GPI by ELISA, were also positive for IgG aCl by chemiluminescence, only 30.13% of patients without clinical manifestations of APS, but positive for aCL and persistently negative for anti-β2-GPI (by ELISA) and LA, confirmed the positive test by chemiluminescence. This difference was highly significant (p<0.0001). Interestingly, this test also prompted to identify 20% of patients positive for LA, but persistently negative for both aCL and anti-β2-GPI IgG (ELISA). Thus, the new technology of automated chemiluminescence assay for measuring aPL may represent an useful tool to identify "true" APS patients.