anti-β2GPI Antibodies Research Articles

Risk prediction of new-onset thrombocytopenia in patients with systemic lupus erythematosus: a multicenter prospective cohort study based on Chinese SLE treatment and research group (CSTAR) registry

BackgroundThrombocytopenia (TP) is a hematological manifestation of systemic lupus erythematosus (SLE) and is associated with unfavorable prognostic outcomes. This study aimed to develop a risk prediction model for new-onset TP in SLE patients.MethodsBased on the multicenter prospective Chinese SLE Treatment and Research Group (CSTAR) registry, newly diagnosed SLE patients without TP at registration were enrolled. The least absolute shrinkage and selection operator (LASSO) method was used for variable selection. The final model was developed using multivariate Cox regression and displayed as a nomogram. Internal validation was achieved using enhanced Bootstrap resampling.ResultsDuring follow-up, thrombocytopenia developed in 80 (3.52%) of 2270 lupus patients. The final risk prediction model incorporated six predictors: baseline SDI score ≥ 1 (HR 2.207, 95% CI 1.350–3.609, p = 0.002), hemolytic anemia (HR 1.953, 95% CI 1.017–3.750, p = 0.044), low complement level (HR 2.351, 95% CI 1.004–5.505, p = 0.049), positive anti-β2GPI antibody (HR 1.805, 95% CI 1.084–3.004, p = 0.024), positive Coombs test (HR 1.878, 95% CI 1.123–3.141, p = 0.017), and positive anti-histone antibody (HR 1.595, 95% CI 1.017–2.587, p = 0.059). The model’s performance was indicated by C-index values for risk prediction at one, two, and three years, which were 0.741 (0.660–0.823), 0.730 (0.655–0.805), and 0.710 (0.643–0.777), respectively; and Brier scores of 0.018 (0.012–0.024), 0.025 (0.017–0.032), and 0.037 (0.027–0.046), respectively. Calibration curves were drawn and situated near the diagonal line.ConclusionsThis study developed the first risk prediction model for TP onset in lupus patients. Patients with baseline organ damage, hemolytic anemia, low complement, positive anti-histone antibody, positive anti-β2GPI antibody, or positive Coombs test were identified as being at high risk for thrombocytopenia and require further clinical attention.

Establishment of cutoff values for anti-β2 glycoprotein I antibodies in women of reproductive age in Southwest China

Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by vascular thrombosis and obstetric morbidity, with accurate laboratory examination of antiphospholipid antibodies (aPLs) being crucial for diagnosis. This study focused on anti-β2 glycoprotein I (aβ2GPI) antibodies and aimed to establish the first population-based cutoff values for aβ2GPI IgA/IgM/IgG antibodies in non-pregnant women of reproductive age in Southwest China. The study cohort comprised 181 healthy women of reproductive age for study. Blood samples were collected on an early morning fast. Anti-β2GPI antibodies including IgA, IgM and IgG were measured in serum using the HOB® BioCLIA kit. According to the Clinical and Laboratory Standards Institute (CLSI) guidelines, the study used non-parametric percentile methods to calculate the 95th, 97.5th, and 99th percentiles cutoff values for aβ2GPI IgA/IgM/IgG antibodies, along with corresponding 90% confidence intervals (CI), while excluding outliers. A total of 168 independent samples were collected for verification, including 85 samples from healthy subjects and 83 samples from APS patients, in order to evaluate the analytical performance of the obtained cutoff values. The 99th percentile cutoff values were 3.36 RU/mL for aβ2GPI IgA, 27.54 RU/mL for aβ2GPI IgM and 1.81 RU/mL for aβ2GPI IgG, which indicated that the levels of aβ2GPI IgM antibodies were generally higher compared to those of IgA and IgG antibodies. Our established reference range was confirmed to be successful in validating the detected values of aβ2GPI antibodies in all healthy controls. With the 99th percentile cutoff value, the sensitivity was 14.46% for aβ2GPI IgA, 22.89% for aβ2GPI IgG, and 9.64% for aβ2GPI IgM in APS patients. This study established population-based cutoff values that are applicable to the local population for the accurate laboratory examination of aβ2GPI antibodies in non-pregnant women of reproductive age. The study also recommends paying more attention to IgM positivity in women of reproductive age.

Correlation between neuropsychiatric systemic lupus erythematosus and immunological markers: a real-world retrospective study.

This study aimed to investigate disparities in clinical profiles and autoantibody patterns between patients with and without neuropsychiatric systemic lupus erythematosus (NPSLE) in a cohort and to identify risk factors associated with NPSLE in the Chinese population. SLE patients were retrospectively reviewed from two tertiary hospitals. The relationships between NPSLE and immunological biomarkers were explored. Among the 945 SLE patients, 75 (7.94%) were diagnosed with NPSLE. The most prevalent NP manifestations involved cognitive disorder (30.67%), headache (26.67%), seizure disorder (26.67%), and psychosis (26.67%).We observed significant associations between psychosis and anti-β2GPI antibodies (F = 6.092, p = 0.015), polyneuropathy and anti-Scl70 antibodies (F = 20.161, p < 0.001), demyelinating syndrome and anti-cardiolipin antibodies (F = 6.637, p = 0.011), myasthenia gravis and anti-RNP (F = 5.864, p = 0.017), and anti-Smith antibodies (F = 5.096, p = 0.026). Multivariate logistics analysis showed that anti-prothrombin (aPT) IgM antibodies (OR = 10.985, CI 1.279-94.343, p = 0.029), age (OR = 1.169, CI 1.032-1.325, p = 0.014), and serum creatinine (SCr) (OR = 1.014, CI 1.003-1.025, p = 0.009) were independent risk factors of NPSLE, while anti-Sjogren syndrome antigen B (SSB) antibodies (OR 0.023, CI 0.002-0.622, p = 0.023) and high complement C3 (OR = 0.001, CI 0-0.045, p < 0.001) indicated reduced risk of NPSLE. Various neuropsychiatric manifestations in SLE were found to be correlated with specific autoantibodies. Independent risk factors for NPSLE included aPT IgM antibodies, age, and elevated serum creatinine, while the absence of anti-SSB antibodies and low complement C3 levels were associated with increased risk. •Significant associations were found between specific autoantibodies and neuropsychiatric symptoms, shedding light on potential biomarkers for predicting and understanding NPSLE. •The study identifies independent risk factors for NPSLE in the Chinese population, including the presence of anti-prothrombin IgM antibodies, older age, elevated serum creatinine, and lower complement C3 levels.

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.

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 toour in-house ELISAs used for over two decades, and to evaluate their diagnostic performance. 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. 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. 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.

IgA Anti-β2-Glycoprotein I Antibodies as Markers of Thrombosis and Severity in COVID-19 Patients.

Patients with COVID-19 may develop a hypercoagulable state due to tissue and endothelial injury, produced by an unbalanced immune response. Therefore, an increased number of thromboembolic events has been reported in these patients. The aim of this study is to investigate the presence of antiphospholipid antibodies (aPL) in COVID-19 patients, their role in the development of thrombosis and their relationship with the severity of the disease. In this retrospective study, serum samples from 159 COVID-19 patients and 80 healthy donors were analysed for the presence of aPL. A total of 29 patients (18.2%) and 14 healthy donors (17.5%) were positive for aPL. Nineteen COVID-19 patients (12%) but no healthy donor presented a positive percentage of the IgA isotype aPL. IgA anti-β2-glycoprotein I antibodies (anti-β2GPI) were the most frequent type (6.3%) in patients but was not detected in any healthy donor. The positivity of this antibody was found to be significantly elevated in patients with thromboembolic events (25% vs. 5%, p = 0.029); in fact, patients with positive IgA anti-β2GPI had an incidence of thrombosis over six times higher than those who had normal antibody concentrations [OR (CI 95%) of 6.67 (1.5-30.2), p = 0.014]. Additionally, patients with moderate-severe disease presented a higher aPL positivity than patients with mild disease according to the Brescia (p = 0.029) and CURB-65 (p = 0.011) severity scales. A multivariate analysis showed that positivity for IgA anti-β2GPI is significantly associated with disease severity measured by CURB-65 [OR (CI 95%) 17.8 (1.7-187), p = 0.0016]. In conclusion, COVID-19 patients have a significantly higher positive percentage of the IgA isotype aPL than healthy donors. IgA anti-β2GPI antibodies were the most frequently detected aPL in COVID-19 patients and were associated with thrombosis and severe COVID-19 and are thus proposed as a possible marker to identify high-risk patients.

Prevalence, Domain Specificity, and Residue Specificity of IgG, IgM, and IgA Anti-β2GPI Antibodies in Tetra-Positive Antiphospholipid Syndrome Patients: Identification of Two Non-Overlapping Epitopes in Domain I of β2GPI

Background. Risk stratification of antiphospholipid syndrome (APS) patients involves several laboratory tests, including lupus anticoagulant (LAC), anti-cardiolipin antibodies (anti-CL), anti-β2GPI antibodies (anti-β2GPI), and, more recently, anti-phosphatidylserine/prothrombin antibodies (anti-PS/PT). Patients with positive results for all four tests, known as tetra-positive APS patients, are considered at high risk for thrombotic recurrence. β2GPI is a protein composed of five domains: DI, DII, DIII, DIV, and DV, arranged in a flexible elongated structure. Previous studies have demonstrated that DI is frequently targeted by IgG in thrombotic APS patients. However, the prevalence, domain specificity, and residue specificity of the three different isotypes of anti-β2GPI antibodies in tetra-positive APS patients remain unknown. Objective. To establish the prevalence, domain specificity, and residue specificity of IgG, IgM, and IgA anti-β2GPI antibodies in tetra-positive APS patients. Methods. Plasma samples from 32 clinically confirmed tetra-positive APS patients and 8 healthy controls were analyzed for levels of IgG, IgM, and IgA using an enzyme-linked immunosorbent assay (ELISA) with immobilized β2GPI as the antigen. Domain and residue mapping were investigated using five deleted domain variants and eight single-point mutations. Mutants lacking specific disulfide bonds were used to assess whether the epitopes targeted by the antibodies are linear or conformational. Results. Among the 32 patients tested, 31 (96%) had IgG, 18 (56%) had IgM, and 18 (56%) had IgA anti-β2GPI antibodies. Ten patients (31%) had all three isotypes, 7 (22%) had IgG and IgM, and 8 (25%) had IgG and IgA. Six patients (19%) had only IgG, 1 had only IgM, and none had only IgA. The removal of DI from the β2GPI molecule led to an almost complete loss of binding (~80%) for the majority of IgG antibodies. There was a lesser but still significant reduction in binding when DII and DV were removed. However, no loss of binding was observed with variants lacking DIII and DIV. Notably, IgA antibodies behaved similarly to IgG but differently from IgM, as their reactivity towards DI and DV was significantly attenuated. To investigate the contribution of specific residues to binding, charged residues K19, E23, E26, E27, R39, R43, K44, and K59 in DI were individually replaced with alanine (A). The most important residue for IgG and IgA antibodies was R43, followed by R39 and K44. In contrast, most residues contributed to optimal binding for IgM antibodies, suggesting a less specific epitope definition. Interestingly, the mutations R39A and K44A often led to loss of binding in conjunction with the mutation R43A, but rarely simultaneously, suggesting the existence of two distinct epitopes for anti-DI antibodies-one located north and one south of R43. Finally, IgG, IgM, and IgA antibodies did not react against the mutant C32S/C60S but showed good reactivity against the mutant C288S/C326S, indicating that epitopes in DI are conformational and require the integrity of the disulfide bond 32-60. Conclusions. In tetra-positive APS patients, IgG anti-β2GPI antibodies are the most prevalent isotype, followed by IgA and IgM. The IgG and IgA isotypes exhibit a pronounced preference for DI, while the IgM isotype demonstrates lower specificity, which aligns with IgM's role as initial responders in infections. Notably, our research revealed that anti-DI antibodies are diverse, as they recognize epitopes within DI that are closely related but physically distinct. Ongoing studies aim to further characterize these antibody subtypes and understand their significance in APS. This knowledge may inform improved diagnostic and therapeutic approaches for APS patients.

16th International congress on antiphospholipid antibodies task force report on antiphospholipid syndrome laboratory diagnostics and trends.

Classification criteria for antiphospholipid syndrome (APS) require IgG or IgM isotypes of the anticardiolipin (aCL) antibodies, anti-β2 glycoprotein I (anti-β2GPI) antibodies, and/or the lupus anticoagulant (LA) to satisfy the laboratory disease definition. Over the past 20 years, non-criteria antiphospholipid antibodies (aPL) directed to other proteins of the coagulation cascade (i.e. prothrombin and/or phosphatidylserine-prothrombin complex) or to some domains of β2GPI have been proposed. This task force concentrated and reviewed the literature on data including aPS/PT, antibodies to domain 4/5 of β2GPI and the newly described antibodies to protein/HLA-DR complex. In addition, we discussed testing of LA in the 'new' oral anticoagulants' era and the value of triple positivity in the risk assessment of aPL. The conclusions were presented at a special session during the 16th International Congress on aPL, Manchester, UK, September 2019.

Development and external validation of a prediction model for venous thromboembolism in systemic lupus erythematosus

ObjectivePatients with systemic lupus erythematosus (SLE) have an increased risk of venous thromboembolism (VTE). We conducted this study to develop a risk score algorithm for VTE in patients with SLE...

Mild-to-moderate COVID-19 does not predispose to the development of autoimmune rheumatic diseases or autoimmune-based thrombosis.

An infection with severe acute respiratory syndrome coronavirus (SARS-CoV-2) may have a significant impact on the human immune system. Interactions between the virus and defence mechanisms may promote the development of autoimmune processes which manifest as antinuclear antibody (ANA) synthesis. Since many different viruses are suspected to take part in the pathogenesis of different systemic autoimmune rheumatic diseases (SARDs), we examined whether coronavirus disease 2019 convalescents who suffer from mild to moderate disease have a higher risk of developing ANA and anti-β2-glicoprotein I IgG antibodies (β2 GPI). In a retrospective study, we examined 294 adults among volunteer blood donors divided into convalescents (N = 215) and healthy controls (N = 79). For ANA detection, we used line-blotting, a type of indirect immunofluorescence assay (IF), to determine antigenic specificity and ELISA for β2 GPI. We found a lower incidence of ANA in convalescents than in healthy controls, with the majority of these antibodies directed to antigens with no known clinical significance. Additionally, no participants were positive for β2 GPI in either group. Our results show that COVID-19 with mild to moderate symptoms in the generally healthy population does not induce the development of ANA or anti-β2 GPI antibodies for at least 6 months following the disease.

Anti–β2-glycoprotein I and anti-phosphatidylserine/prothrombin antibodies interfere with cleavage of factor V(a) by activated protein C

BackgroundThe acquired thrombotic risk factor known as lupus anticoagulant (LA) interferes with laboratory clotting assays and can be caused by autoantibodies against β2-glycoprotein I (β2GPI) and prothrombin. LA is associated with activated protein C (APC) resistance, which might contribute to thrombotic risk in patients with antiphospholipid syndrome. How antibodies against β2GPI and prothrombin cause APC resistance is currently unclear. ObjectivesTo investigate how anti-β2GPI and antiphosphatidylserine/prothrombin (PS/PT) antibodies induce APC resistance. MethodsThe effects of anti-β2GPI and anti-PS/PT antibodies on APC resistance were studied in plasma (of patients with antiphospholipid syndrome) and with purified coagulation factors and antibodies. ResultsAPC resistance was observed in LA-positive patients with anti-β2GPI or anti-PS/PT antibodies and in normal plasma spiked with monoclonal anti-β2GPI or anti-PS/PT antibodies with LA activity. Analysis of factor (F)V cleavage patterns after APC incubation indicated that anti-β2GPI antibodies attenuated APC-mediated FV cleavage at R506 and R306. APC-mediated cleavage at R506 is required for FV cofactor activity during inactivation of FVIIIa. Assays with purified coagulation factors confirmed that anti-β2GPI antibodies interfered with the cofactor function of FV during FVIIIa inactivation but not with FVa inactivation. Anti-PS/PT antibodies attenuated APC-mediated FVa and FVIIIa inactivation. Analysis of FV(a) cleavage patterns after APC incubation indicated that anti-PS/PT antibodies interfere with APC-mediated cleavage of FV at positions R506 and R306. ConclusionAnti-β2GPI antibodies with LA activity contribute to a procoagulant state by causing APC resistance via interference with the cofactor function of FV during FVIIIa inactivation. LA-causing anti-PS/PT antibodies interfere with the anticoagulant function of APC by preventing FV(a) cleavage.

Fluctuation of Anti-Domain 1 and Anti-β2 -Glycoprotein I Antibody Titers Over Time in Patients With Persistently Positive Antiphospholipid Antibodies.

The present study was undertaken to longitudinally evaluate titers of antibodies against β2 -glycoprotein I (anti-β2 GPI) and domain 1 (anti-D1), to identify predictors of variations in anti-β2 GPI and anti-D1 titers, and to clarify whether antibody titer fluctuations predict thrombosis in a large international cohort of patients who were persistently positive for antiphospholipid antibodies (aPL) in the APS ACTION Registry. Patients with available blood samples from at least 4 time points (at baseline [year 1] and at years 2-4 of follow-up) were included. Detection of anti-β2 GPI and anti-D1 IgG antibodies was performed using chemiluminescence (BIO-FLASH; INOVA Diagnostics). Among 230 patients in the study cohort, anti-D1 and anti-β2 GPI titers decreased significantly over time (P < 0.0001 and P=0.010, respectively). After adjustment for age, sex, and number of positive aPL tests, we found that the fluctuations in anti-D1 and anti-β2 GPI titer levels were associated with treatment with hydroxychloroquine (HCQ) at each time point. Treatment with HCQ, but not immunosuppressive agents, was associated with 1.3-fold and 1.4-fold decreases in anti-D1 and anti-β2 GPI titers, respectively. Incident vascular events were associated with 1.9-fold and 2.1-fold increases in anti-D1 and anti-β2 GPI titers, respectively. Anti-D1 and anti-β2 GPI titers at the time of thrombosis were lower compared to titers at other time points. A 1.6-fold decrease in anti-D1 titers and a 2-fold decrease in anti-β2 GPI titers conferred odds ratios for incident thrombosis of 6.0 (95% confidence interval [95% CI] 0.62-59.3) and 9.4 (95% CI 1.1-80.2), respectively. Treatment with HCQ and incident vascular events in aPL-positive patients predicted significant anti-D1 and anti-β2 GPI titer fluctuations over time. Both anti-D1 and anti-β2 GPI titers decreased around the time of thrombosis, with potential clinical relevance.

Clinical characteristics of 37 antiphospholipid syndrome patients complicated by autoimmune hemolytic anemia

Objective: We sought to investigate the clinical characteristics and risk factors of antiphospholipid syndrome (APS) complicated by autoimmune hemolytic anemia (AIHA). Methods: Retrospective anaysis.Three hundred fifteen consecutive patients with APS were enrolled at the Department of Rheumatology of Peking Union Medical College Hospital between May 2017 to May 2021, and their clinical manifestations[including initial symptoms, time interval between APS onset and diagnosis, systemic lupus erythematosus(SLE), thrombotic events, obstetric morbidity, and extra-criteria manifestations] and laboratory test results[including blood routine, antiphospholipid antibodies(aPLs), blood lipid profile, homocysteine, anti-nuclear antibody profile, immunoglobulin levels, and complement levels] were collected. Then, univariate and multivariate logistic regression analyses were performed. Clinical features and risk factors were analyzed using univariable and multivariable logistic regression analysis. Results: Among 315 APS patients, 37 cases (11.7%) were complicated by AIHA, and AIHA was the first manifestation or co-occurrence. The median time interval between APS onset and diagnosis was 12 months. The proportion of SLE in APS patients combined with AIHA was higher than that in APS patients without AIHA[62.2%(23/37) vs. 19.4%(54/278), P<0.001]. There was no significant difference in the proportions of thrombosis and pregnancy morbidity between the two groups. In terms of extra-criteria manifestations, APS patients with AIHA had a significantly (P<0.05) greater risk of thrombocytopenia (OR=6.19, 95%CI 2.81-13.65) and higher proportions of hypocomplementemia, a positive lupus anticoagulant (LA) result, double aPLs positivity[i.e., any two of the following antibodies were positive: LA, anticardilolipin antibody(aCL), and anti-β2 glycoprotein Ⅰ(β2GPⅠ)], and triple aPLs positivity (i.e., LA, aCL, and anti-β2GPⅠ antibodies were all positive). Multivariate logistic regression analysis showed that SLE (OR=3.46,95%CI 1.60-7.48), thrombocytopenia (OR=2.56,95%CI 1.15-5.67), and hypocomplementemia (OR=4.29,95%CI 2.03-9.04) were independent risk factors for the complication of APS. In the primary APS subgroup, multivariate logistic regression analysis showed that livedo reticularis (OR=10.51,95%CI 1.06-103.78), thrombocytopenia (OR=3.77, 95%CI 1.23-11.57), and hypocomplementemia (OR=5.92,95%CI 1.95-17.95) were independent risk factors for the complication of APS. Conclusions: AIHA is not rare in APS patients; moreover, it occurs more frequently in APS secondary to SLE and is more likely to present with a variety of extra-criteria manifestations. Patients with AIHA should be promptly tested for antiphospholipid antibody profiles and alerted to the possibility of thrombotic events.

The Risk of Autoimmunity Development following mRNA COVID-19 Vaccination.

The broad spectrum of interactions between autoimmune diseases and the SARS-CoV-2 vaccination is not fully understood. This study aims to evaluate the prevalence of anti-nuclear antibodies (ANA), anti-ENA, anticardiolipin antibodies (ACL), and anti-beta-2 glycoprotein I antibodies (anti-β2GPI) before and after the SARS-CoV-2 mRNA vaccination in a real-life setting in healthcare professionals. The identification of risk factors associated with vaccine immunogenicity was evaluated. The study group consisted of employees of two hospitals (354 individuals). Samples for antibody assays were collected before vaccination and at 7-9 months after complete immunisation. There was no significant increase in the prevalence of ANA, ACL or anti-β2GPI antibodies, or autoimmune diseases in subjects who were vaccinated 7-9 months after complete immunisation. In terms of detected anti-ENA, the anti-DFS70 antibodies were found in 6 times more subjects than before vaccination at the second blood draw (in 18 and 3 subjects, respectively) (p = 0.001). There were no significant relationships between a SARS-CoV-2 infection history, humoral response, cellular response, subject category, smoking, sex, body weight, ANA, anti-ENA, ACL, or anti-β2GPI. This study revealed a possible association between the severity of vaccine adverse events (VAEs) and ANA titre. Individuals with more severe VAEs (&gt;10 points) after the second dose of the vaccine had significantly higher ANA titre after complete immunization. When analysing the significance of time between the ANA, anti-ENA, ACL, and anti- β2GPI assays and complete immunisation antibody values, no qualitative result was statistically significant. There was correlation between the time since complete immunization and ANA after.

Assessing the Rate of Compliance with the Revised Sapporo/Sydney Criteria in Diagnosing Antiphospholipid Syndrome: A Multicenter Retrospective Analysis

Background: Antiphospholipid syndrome (APS) is a systemic autoimmune disease defined by thrombotic or obstetrical events in patients with persistent elevation of antiphospholipid antibodies (aPL) (Lim, 2013). The revised Sapporo/Sydney criteria has been adopted by most professional societies as a guidance to APS diagnosis. To be diagnosed with APS, a patient has to meet at least one clinical criteria and one laboratory criteria. Clinical criteria includes either vascular thrombosis or an adverse outcome during pregnancy. The lab criteria consist of the presence of one or more specified aPL, identified on two or more occasions, at least 12 weeks apart (Miyakis et al., 2006). Antibody testing in patients with suspected APS involves immunoassays for IgG and IgM antibodies to cardiolipin (aCL), and beta2-glycoprotein I (anti-β2GPI), as well as a functional assay for the lupus anticoagulant (LA) phenomenon (Miyakis et al., 2006). Testing asymptomatic individuals is not recommended and carries a significant rate of false positivity, given that up to 10% of healthy individuals may have transient aPL elevation (Vila et al., 1994). Furthermore, certain medications, infections, malignancies, autoimmune diseases, and rheumatologic diseases can also induce transient elevation of aPL antibodies without associated thrombotic complications, emphasizing the importance of repeated aPL measurements in the diagnosis (Lim, 2013; Rand & Wolgast, 2012). Weakly positive levels of aCL and anti-β2GPI antibodies should not be considered significant. Most authorities require Ab levels to be at or above the 99th percentile to be considered clinically significant (Rand & Wolgast, 2012). We aim to assess the compliance with revised Sapporo/Sydney criteria in diagnosing APS in our community hospital system. Methods: We conducted a multi-center, retrospective study among adult patients who were diagnosed with APS in a community healthcare system in southeast Michigan. Demographic and clinical characteristics were collected along with history of venous thrombosis, arterial thrombosis, pregnancy complications, aPL testing results and use of anticoagulants. We used SAS for exploratory data analysis and descriptive statistics. Results: A total of 781 patients were diagnosed with APS between August 2016 to December 2021 (table 1). The median age at diagnosis was 51.3 years (interquartile range 18-93 years). 639 (81.8%) patients were females and 142 (18.2%) were males. Majority of patients were white (n=563, 72.1%). 570 (73.0%) patients had history of venous or arterial thrombosis, 309 (49.9%) had pregnancy complications included in the revised Sapporo/Sydney criteria, and 211 (27.0%) had neither history of thrombosis nor pregnancy complications, not meeting the clinical criteria for APS diagnosis. 528 (67.6%) patients did not meet the laboratory criteria for the diagnosis (figure 1). Of these patients, 439 (83.1%) did not have a repeated testing of aPL antibodies.88 (16.7%) had weakly positive levels of aCL and anti-β2GPI antibodies, below the 99th percentile, and 1 (0.2%) had repeated antibodies testing in less than12 weeks. Out of 528 patients who did not meet the laboratory criteria, 321 (60.8%) were started on anticoagulants. Of these 321 patients, 135 (42%) did not have any history of thrombosis or other appropriate indication of anticoagulation, such as atrial fibrillation. Of 321 patients who were treated with anticoagulation, warfarin was the most prescribed accounting in 120 patients (37.4%). The remainder of patients (62%) were treated with apixaban, rivaroxaban or enoxaparin. Conclusion: Our results showed poor compliance with the current guidelines in both selecting the appropriate candidate for testing, and interpreting aPL testing results, leading to an alarmingly high rate of false diagnosis of APS. Obtaining a positive aPL test result in an otherwise disease-free individual can contribute to unnecessary anticoagulation and side effects including bleeding and increased cost burden to patients and families. Therefore, caution must be exercised while ordering aPL tests and adherence to current guidelines should be encouraged in the routine clinical settings. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Antiphosphatidylserine/prothrombin antibodies (aPS/PT) and risk of obstetric anti-phospholipid syndrome.

Assessment of the prevalence of anti-phosphatidylserine-prothrombin antibodies (aPS/PT) with OAPS and SN-OAPS in Chinese patients. This retrospective study proceeded at Ren Ji Hospital, Shanghai, China, from January 2019 to January 2020. Two hundred eleven OAPS, 68 SN-OAPS, 81 disease controls, and 30 healthy donors were enrolled. IgM and IgG aPS/PT, IgM/IgG - aCL, and IgM/ IgG/ anti-β2GPI antibodies were tested by ELISA while LAC was tested by clotting assays. All the patients were followed up and tested at least twice over 12weeks apart. Thirty-three OAPS (15.64%) and 31 SN-OAPS (45.59%) were positive for aPS/PT. aPS/PT IgM showed a high Youden index (.813), which classified OAPS and SN-OAPS patients from healthy controls and other autoimmune diseases. aPS/PT showed a stronger relationship with LAC. Of the 25 OAPS women positive for IgM aPS/PT, 19 (79%) LAC were positive, while of the eight women positive for IgG aPS/PT, 100% were found LAC positive. aPS/PT antibody showed an efficient diagnostic value for Chinese patients with OAPS and SN-OAPS, which could be a potential risk predictor for obstetric complications.

Determinación del percentil 99 de los anticuerpos anticardiolipina y anti-β2 glicoproteína I en una institución en la ciudad de Medellín, Colombia

IntroductionAntiphospholipid syndrome diagnosis requires abnormal results of lupus anticoagulant and high titles of anticardiolipin (aCL) and β2glycoprotein I (anti-β2GPI) antibodies. The latter immunological tests lack a standard threshold in clinical practice. ObjectiveTo determine the 99th percentile of aCL and anti-β2GPI in healthy volunteers. Materials and methodsThis cross-sectional study reviewed antibody titles of anticardiolipin and β2glycoprotein I (IgG and IgM by enzyme-linked immunosorbent assay) in forty-nine healthy blood donors in Medellin, Colombia. Sociodemographic and immunological variables are also assessed. Antibody titles are described in median and interquartile range and the 99th percentile was estimated. ResultsWe analysed samples from 16 men and 33 women. We found that the upper limits of the reference range (99th percentile) of aCL and anti-β2GPI were: aCL IgM: 18.0, aCL IgG: 16.1, anti-β2GPI IgM: 16.4, and anti- β2GPI IgG: 6.9. ConclusionsThe upper limits obtained differ greatly from the arbitrary classification values suggested in the international guidelines, taking into account that values greater than 40 international units are usually required, and the values identified in this study are between 6.9 and 18 international units. We suggest conducting additional studies that validate cut-off points according to the percentiles explored in this work.

Antiphospholipid Antibody Assays in 2021: Looking for a Predictive Value in Addition to a Diagnostic One.

Antiphospholipid antibodies (aPL) are mandatory for the diagnosis but are also a risk factor for the antiphospholipid syndrome (APS) clinical manifestations. Lupus anticoagulant (LA), anticardiolipin (aCL), and anti-beta2 glycoprotein I (β2GPI) assays are the formal laboratory classification/diagnostic criteria. Additional nonclassification assays have been suggested; among them, antiphosphatidylserine-prothrombin (aPS/PT) and antidomain 1 β2GPI antibodies are the most promising ones although not yet formally accepted. aPL represent the example of a laboratory test that moved from dichotomous to quantitative results consistent with the idea that reporting quantitative data offers more diagnostic/prognostic information for both vascular and obstetric manifestations. Although the general rule is that the higher the aPL titer, the higher the test likelihood ratio, there is growing evidence that this is not the case for persistent low titers and obstetric events. LA displays the highest diagnostic/prognostic power, although some isolated LAs are apparently not associated with APS manifestations. Moreover, isotype characterization is also critical since IgG aPL are more diagnostic/prognostic than IgA or IgM. aPL are directed against two main autoantigens: β2GPI and PT. However, anti-β2GPI antibodies are more associated with the APS clinical spectrum. In addition, there is evidence that anti-β2GPI domain 1 antibodies display a stronger diagnostic/prognostic value. This finding supports the view that antigen and even epitope characterization represents a further step for improving the assay value. The strategy to improve aPL laboratory characterization is a lesson that can be translated to other autoantibody assays in order to improve our diagnostic and prognostic power.

Preoperative bleeding risk assessment with ISTH-BAT and laboratory tests in patients undergoing elective surgery: A prospective cohort study.

Patients with inherited haemorrhagic disorders may bleed during surgery. No questionnaire on bleeding diathesis has been yet validated for the preoperative period and current guidelines provide conflicting recommendations. We aimed to assess if preoperative assessment with ISTH-BAT (International Society on Thrombosis and Haemostasis Bleeding Assesment Tool) and laboratory screening tests is useful to identify mild previously undiagnosed bleeding disorders (BDs) and to predict bleeding complications in selected patients undergoing elective surgery. Consecutive patients undergoing elective surgery received ISTH-BAT evaluation and laboratory screening for platelet count, Prothrombin Time (PT) and activated Partial Thromboplastin Time (aPTT). Subjects with an abnormal ISTH-BAT and/or laboratory results underwent further testing, and they were compared with a 1:1 random gender-, age- and type of surgery- matched control group. Overall, 1502 consecutive surgical patients (1186 adults, 316 children) were enrolled. Of these, 83 (5.5%, 95% confidence interval 4.4-6.8) patients (37 adults and 46 children) had an abnormal ISTH-BAT, and/or prolonged PT and/or prolonged aPTT and/or low platelet count; of them, one subject had low von Willebrand factor level, three Factor XII deficiency and four anticardiolipin and/or antiB2GPI antibodies. No major bleeding was reported in these 83 patients and their controls. ISTH-BAT and laboratory screening tests do not accurately detect mild BDs in selected patients undergoing elective surgery.

Relevance of autoantibody profile with HLA-DRB1 and -DQB1 alleles in a group of Iranian systemic lupus erythematosus patients

BackgroundOne of the most relevant genetic components in systemic lupus erythematosus (SLE) is human leukocyte antigen (HLA) gene complex which plays a central role in autoimmune responses. This study aimed to explore the associations of HLA-DRB1/-DQB1 alleles and haplotypes with SLE risk and the appearance of autoantibodies in SLE disease. MethodsA total of 127 SLE patients and 153 ethnically matched healthy controls were enrolled. HLA-DRB1 and HLA-DQB1 alleles were determined by PCR-SSP method and then HLA alleles and haplotypes frequencies were compared between two groups and among the patients in terms of autoantibodies spectrum. ResultsWe found that HLA-DRB1*03 and HLA-DRB1*16 alleles were significantly associated with increased risk (P = 0.008, PC=0.05 and P = 0.002, PC=0.02 respectively) and DRB1*01 conferred a potential protective role for disease (P = 0.03, PC=0.13). Similar associations were observed at haplotype level; DRB1*03~DQB1*02 (OR1.91,P = 0.01, PC=0.08), DRB1*16~DQB1*05 (OR3.65,P = 0.004,PC=0.06) and DRB1*01~DQB1*05 (OR0.36,P = 0.04, PC=0.22). Remarkably, we observed significantly associations of DRB1*03 with the appearance of anti-SSA/Ro (PC=0.02), anti-SSB/La (PC=0.002) and anti-coagulant (P = 0.007), DRB1*15 with anti-SSA/Ro (PC=0.04), DRB1*16 with anti-Sm (PC=0.02), DRB1*04 with anti-β2gpI (PC=3 * 10−5), anti-cardiolipin (P = 0.002) and rheumatoid factor (P = 0.004) and DRB1*13 with anti-Sm (PC=0.02) and anti-β2gpI (PC=0.01) antibodies. Also, negative associations of DRB1*04 with anti-Sm, anti-SSA/Ro, DQB1*03 with anti-Sm and DRB1*11 with anti-Sm and anti-β2gpI were observed. ConclusionsWe identified DRB1*03 and DRB1*16 as risk alleles and DRB1*01 as a potential protective allele for SLE disease. More importantly, we found a close link between genetic susceptibility for SLE and autoantibodies status that was more evident for DRB1*03 allele.

Small Angle X-Ray Scattering Reveals the Conformation of β2glycoprotein I and the Conformational Binding Epitopes of Autoantibodies

Despite the fact that autoantibodies to a variety of antigens have been described in patients with the antiphospholipid syndrome (APS), it is now generally accepted that β2glycoprotein I (β2GPI) is a primary target of pathogenic autoantibodies in APS patients. Unraveling the immunodominant epitope of β2GPI at the molecular/conformational level may help to understand the disease and develop specific therapies. β2GPI is an abundant plasma protein that, upon interaction with negative phospholipids, has been shown to undergo a conformational change resulting in the exposure of a pathogenic epitope on domain I. Although the conformation of β2GPI has been previously reported by small angle X-ray scattering (SAXS), we are the first to show the interaction with autoimmune anti-β2GPI antibodies. We previously showed that antibodies towards the cryptic domain I epitope are highly associated with both thrombosis and pregnancy morbidity. Previous studies indicated that amino acids R39-R43 and the interlinking region between domains I and II are part of this cryptic epitope. However, these studies used point-mutated variants of β2GPI, and the results could be influenced by structural changes compared to native β2GPI.In this study, we visualized the conformation of β2GPI in solution by SAXS and its interaction with two anti-domain I antibodies, obtained via B cell isolation from two APS patients. Antibody P2-6 previously showed affinity for domain I regardless of the conformation of β2GPI, whereas antibody P1-117 only recognized domain I of β2GPI upon binding to anionic phospholipids. Via point-mutated variants of β2GPI we previously demonstrated that P1-117 is reactive against the cryptic domain I epitope including epitope G40-R43. In a first set of SAXS experiments, we visualized plasma purified β2GPI in its native conformation. We found that, due to the flexibility of domain I-III of β2GPI, β2GPI is able to adapt into several different conformations ranging from a sort of circular shape into a S shape, confirming results of previous studies. Upon increasing the pH, the conformation of β2GPI changed into a more erect fish-hook conformation resembling the crystal structure of β2GPI. The three-dimensional structures of both antibodies were determined by SAXS and allowed to react with β2GPI in the open conformation (Figure 1). Antibody P2-6 interacted mainly with the amino terminal end of domain I of β2GPI which is available in both the native and open conformations of β2GPI. In contrast, antibody P1-117 interacted with a broader part of the protein, identifying a discontinuous and conformational epitope covering domain I, the interlinking region and a small part of domain II. Importantly, (part of) the epitope is not available in the native closed conformation of β2GPI due to its interaction with domain V (circular conformation) or due to a carbohydrate chain positioned on the interface of domain I-II (S shaped conformation). These data confirm the importance of the conformation of β2GPI coated on the solid phase of diagnostic anti-β2GPI assays to avoid false negative classification of APS patients.In conclusion, our findings contribute to elucidating the conformation of β2GPI in solution and clearly indicate that pathogenic autoantibodies bind a discontinuous conformational epitope. Identification of this conformational epitope will allow optimization of peptide-based therapies and also epitope-specific diagnostic assays that will enable the stratification of patients according to their risk on thrombosis/pregnancy morbidity. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.