Evaluation of different immunoassays for the detection of antiphospholipid antibodies: Report of a wet workshop during the 13th International Congress on Antiphospholipid Antibodies

Quantification of Antiphospholipid Antibodies: The Importance of Using an Appropriate Methodology for Each Clinical Profile

The presence of antiphospholipid antibodies (aPLs) is associated with antiphospholipid syndrome (APS), characterized by thrombosis and obstetric morbidity. aPLs included in APS classification criteria are lupus anticoagulant, anti-cardiolipin and anti-beta-2-glycoprotein-I of IgG or IgM isotypes. Enzyme-linked immunosorbent assay is the most used diagnostic technique to determine aPLs. Recently, new automated technologies mainly based in antigen-coated beads have been developed. The aim is to compare a fluorescence enzyme immunoassay (M1) and an antigen-coated bead assay (M2) in obstetric and thrombotic APS patients. All samples from the first 1020 patients received in the Immune Service Laboratory (Hospital 12 de Octubre) during the recruitment period, without exclusions, were analysed for aPLs. The weighted kappa for both methods in all the patients was 0.39 (0.30-0.47). Agreement increased to 0.56 (0.38-0.73) in patients with autoimmune disease. Sensitivity and specificity obtained for M1 were 17.1% and 89.3%, respectively, and 12.7% and 91.4% for M2. The sensibility and specificity of IgG isotypes were higher than the IgM ones. Regarding obstetric patients, M1 obtained significant diagnostic performance and had more sensitivity 23.75 (14.95-34.58) compared to M2 12.50 (6.16-21.79). In conclusion, clinical suspicion-based method selection for aPLs should be considered. To identify obstetric APS patients, solid phase methods remain more preferable.

Antiphospholipid antibodies are persistently positive at high titers. Additive value of platelet-bound C4d

Background

Classification criteria for antiphospholipid syndrome (APS) require that antiphospholipid antibody (aPL) positivity is confirmed after at least 12 weeks. We tested the hypothesis that aPL at high titers remain positive while low titers fluctuate over time. As both platelet-bound C4d (PC4d) and aPL are associated with thrombosis in systemic lupus erythematosus (SLE), we also evaluated whether PC4d can aid in APS diagnosis.

Methods

Data from serum or plasma sent to Exagen’s laboratory for routine aPL testing were analyzed. Anti-cardiolipin (aCL) and anti-beta2 glycoprotein-1 antibodies (aB2GP1) were measured by chemiluminescence or ELiA fluorescence enzyme immunoassay; anti-phosphatidylserine/prothrombin complex antibodies (aPS/PT) by ELISA; PC4d by flow cytometry. Statistical analysis included descriptive statistics, logistic regression, and Pearson correlation.

Results

More than 80% of positive samples with aCL and aB2GP1 at high titers - but not low titers - were positive at a retest. Non-criteria aPL (aPS/PT) followed a similar trend. aCL and aB2GP1 measured with two different technologies were highly correlated. PC4d and IgG of the three aPL were at best moderately correlated even when only positive aPL samples were analyzed (coefficient: 0.1917 to 0.2649).

Conclusions

High titers aPL are often persistently positive, allowing an earlier diagnosis and risk assessment at the time of the initial screening. Conversely, a retest may be necessary for low titers. The high correlation between two methodologies suggests that these findings are independent of assay platform. The low to moderate correlation between PC4d and aPL might suggest a possible additive value to evaluate association with thrombosis in autoimmune diseases.

Study of antiphospholipid antibodies by enzyme immunoassay and chemiluminescent methods in patients with antiphospholipid syndrome and systemic lupus erythematosus (preliminary data)

Antiphospholipid antibodies (aPL) are a family of different autoantibodies that lead to recurrent vascular thrombosis of any localization and caliber, and/or obstetric pathology - fetal loss. Serological markers of antiphospholipid syndrome (APS) include only three types of aPL - lupus anticoagulant (VA), antibodies to cardiolipin (aCL) classes IgG and IgM, antibodies to β2-glycoprotein1 (aβ2GP1) classes IgG and IgM. Medium and high levels of aCL and aß2HP1 (IgG and / or IgM) were selected as serological markers of APS in the 2006 classification criteria. However, the threshold of values used from low to moderately high levels has not been standardized. aPL standardization issues are still unresolved, resulting in heterogeneous results of the ongoing studies. The aim of the study was to assess the comparability IgG/IgM-aCL and IgG/IgM-ab2GP1 by enzyme-linked immunosorbent assay and chemiluminescent analysis in patients with APS with and without (systemic lupus erythematosus) SLE. The study included 70 patients (49 women and 21 men) with APS, of which 21 (30%) were with primary APS (pAPS) and 49 (70%) with APS in combination with SLE. All study participants underwent determination of IgG/IgM-aCL and IgG/IgM-aβ2GP1 by enzyme-linked immunosorbent. A study was performed by the chemiluminescent analysis: IgG/IgM-aCL - in 70 patients; IgG/IgM-aβ2GP1 - in 69 patients. Results. According to preliminary data, the determination of IgG-aCL and IgG-aβ2GP1 by the chemiluminescent analysis is informative in assessing positivity according to the manufacturer, compared with the enzyme-linked immunosorbent (p < 0.05). However, when taking into account the levels of antibody positivity determined by enzyme-linked immunosorbent, the level of positive values according to chemiluminescent analysis was much higher than the performance of the manufacturer.

Clinical performance of automated chemiluminescent methods for anticardiolipin and anti-β2-glycoprotein I antibodies detection in a large cohort of Chinese patients with antiphospholipid syndrome

INTRODUCTION

To assess the clinical performance and correlations of automated chemiluminescence assay (CIA) and enzyme-linked immunosorbent assay (ELISA) for detecting antiphospholipid (aPL) antibodies in the diagnosis of antiphospholipid syndrome (APS).

METHODS

The study recruited 505 subjects, including 192 with APS, 193 with connective tissue diseases other than APS, and 120 healthy donors. We measured anticardiolipin (aCL) and anti-β2-glycoprotein I (anti-β2GPI) antibodies IgG, IgM, and IgA in all the samples using both CIA and ELISA.

RESULTS

Total agreement between the two methods ranged from 83.50% for anti-β2GPI IgG antibodies to 92.76% for anti-β2GPI IgM antibodies in all the groups. Anti-β2GPI and aCL IgG assays showed the highest Spearman's rho coefficients (anti-β2GPI IgG = 0.742, aCL IgG = 0.715). Anti-β2GPI IgG CIA showed the highest sensitivity for diagnosis of APS at 80.21%, which was significantly higher than the sensitivity of anti-β2GPI IgG ELISA (52.08%). For diagnosis of APS, anti-β2GPI IgG CIA had the best discrimination power with the area under the curves (AUC) of 0.922, followed by aCL IgG CIA (AUC of 0.905). While the CIA AUC was slightly higher in all cases, the difference was not statistically significant.

CONCLUSION

CIA measurements had a good agreement and correlation with comparative ELISA assays. The CIA anti-β2GPI IgG however was significantly more sensitive for APS diagnosis. The two assay methodologies showed comparable predictive powers and support the value of the CIA method for improved diagnosis and management of patients with APS.

Two Novel Technologies for the Detection of Anti-cardiolipin and Anti β2-Glycoprotein Antibodies in the Real Life: Chemiluminescent in Comparison to the Addressable Laser Bead Immunoassays

In the present study, we evaluated two novel technologies, the chemiluminescent immunoassay (CIA) QUANTA Flash on BIO-FLASH (Inova Diagnostics, San Diego, CA, USA) and the addressable laser bead immunoassay (ALBIA) on BioPlex™ 2200 (Bio-Rad, Hercules, CA, USA) for the detection of anti-cardiolipin IgG/IgM (aCL) and anti-β2-glycoprotein IgG/IgM (aβ2GPI) antibodies. The study was performed on 134 samples from consecutive patients (59 males and 75 females, mean age 54 ± 10 years) who consulted a rheumatologist because thrombosis and/or pregnancy complications were present or another immunological disease (Sjogren's syndrome, inflammatory arthritis). Fourteen patients of the total fulfilled 25the Sydney criteria for APS and for these patients previous results of aPLs were available. Sera were tested for aCL and aβ2GPI of IgG and IgM isotypes using CIA (BIO-FLASH) and ALBIA (BioPlex™ 2200). Overall agreement between CIA and ALBIA ranged from 88.1% (aCL IgG) to 97.8% (aβ2GPI IgG). Cohen's kappa coefficient ranged from 0.53 to 0.91, implying moderate to almost perfect agreement. Almost perfect agreement was found between BioPlex™ 2200 and BIO-FLASH aβ2GPI IgG and aCL IgM with Cohen's kappa of 0.91 and 0.88, respectively. On the other hand, moderate agreement was found between BioPlex™ 2200 and BIO-FLASH aCL IgG and β2GPI IgM assays with Cohen's kappa of 0.57 and 0.53, respectively. The two novel technologies look promising and comparable but further studies with larger cohorts are needed to contribute to the better understanding of the new aPLs antibodies assays performance.

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.

Assessment of diagnostic methods for the detection of anticardiolipin and anti-βeta2 glycoprotein I antibodies in patients under routine evaluation for antiphospholipid syndrome

BACKGROUND

We assessed the performance characteristics and correlations of the traditional enzyme-linked immunosorbent assay (ELISA) and chemiluminescence immunoassay (CIA) for detecting IgG and IgM antibodies to cardiolipin (aCL) and beta₂ glycoprotein (anti-β₂GPI) antibodies in patients under routine evaluation for APS.

METHODS

Patients (n = 216) referred to ARUP Laboratories for lupus anticoagulant (LAC) and/or aCL or anti-β₂GPI IgG/IgM antibodies evaluation were assessed by ELISA and CIA methods. Diagnostic accuracies, correlations between methods and specific clinical manifestations in APS were investigated.

RESULTS

The areas under the curve (%) for APS using LAC with CIA (74, 95% CI: 65-82) or ELISA (70, 95% CI: 61-79) aPLs were comparable. The overall agreements and linear regression correlations between methods for aPL antibody of the same specificity were variable: aCL IgG 87.3%; R² = 0.7491, aCL IgM 71.6%; R² = 0.2656, anti-β₂GPI IgG 77.2%; R² = 0.7688 and anti-β₂GPI IgM 81.7%; R² = 0.3305.

CONCLUSIONS

With inclusion of LAC, the ELISA and CIA show comparable performance for the diagnosis of APS. However, correlations of APS-specific manifestations were dependent on method of detecting the aPL antibodies suggesting platforms may not be used interchangeable.

Anti-phospholipid Antibodies and Smoking: An Overview

Antiphospholipid syndrome is characterized by the presence of antiphospholipid antibodies, specifically lupus anticoagulant, anticardiolipin antibodies, and anti-β2 glycoprotein-I antibodies. Antiphospholipid syndrome can occur on its own or in association with other autoimmune diseases, most commonly systemic lupus erythematosus (SLE). A connection between cigarette smoking and anti-phospholipid antibodies (aPL) was first reported in the late1980s. Systemic lupus erythematosus patients with aPL are more likely to be smokers than those without aPL. These patients have a particularly high frequency of vascular events. Recently, a potential link between periodontitis, tobacco, and aPL has been proposed. Research has also suggested that periodontitis and Porphyromonas gingivalis infection are associated with citrullination through the action of peptidylarginine deiminase. A strong correlation between smoking and the presence of citrillunated autoantibodies, which are characteristic of rheumatoid arthritis, has also been observed. While many studies have investigated possible links between infection and aPL in patients with autoimmune diseases, the association of smoking with aPL has not been systematically examined. The fact that both aPL and tobacco are risk factors for thrombosis has complicated efforts to evaluate these factors separately. Also, there has been great variability in measurement techniques, and laboratories lack routine methods for differentiating transient and persistent aPL; both of these factors can make interpretation of autoantibody results quite challenging. This review summarizes the clinical evidence supporting a posited link between aPL and smoking, both in patients with a systemic autoimmune disease and in patients with other medical conditions.

The catastrophic antiphospholipid syndrome in children

PURPOSE OF REVIEW

To review the difficult syndrome of catastrophic antiphospholipid syndrome, emphasizing new developments in the diagnosis, pathogenesis and treatment.

RECENT FINDINGS

Few recent publications directly address pediatric catastrophic antiphospholipid syndrome (CAPS). Most articles are case reports or are data from adult and pediatric registries. The major factors contributing to most pediatric catastrophic antiphospholipid syndrome include infection and the presence of antiphospholipid antibodies, but complement activation also is important in creating diffuse thrombosis in the microcirculation. Treatment of the acute emergency requires anticoagulation, suppression of the hyperinflammatory state and elimination of the triggering infection. Inhibition of complement activation appears to improve outcome in limited studies, and suppression of antiphospholipid antibody formation may be important in long-term management.

SUMMARY

CAPS, an antibody-mediated diffuse thrombotic disease of microvasculature, is rare in childhood but has high mortality (33-50%). It requires prompt recognition and aggressive multimodality treatment, including anticoagulation, anti-inflammatory therapy and elimination of inciting infection and pathogenic autoantibodies.

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.

Evaluation of antiphospholipid antibody assays using latent class analysis to address the lack of a reference standard

BACKGROUND

Method evaluation of new assays for the detection of antiphospholipid antibodies (aPL) such as anti-cardiolipin (aCL) or anti-β2-glycoprotein I (aβ2-GPI) is challenging, as no internationally accepted reference material is available yet. Besides a lack of standardization, unacceptable inter-laboratory comparability of established tests is regularly observed. Owing to the absence of a commonly accepted reference standard, the evaluation of two research surface plasmon resonance (SPR) biosensor assays was performed using statistical methods from latent class analysis (LCA).

METHODS

aCL and aβ2-GPI IgG and IgM were measured in sera from 63 antiphospholipid syndrome patients, fulfilling the Sydney criteria, and in 34 healthy controls with four commercial assays. LCA was performed on the results and sera were assigned to the antibody-positive or antibody-negative group. Sera were subsequently evaluated in the SPR assays for aCL and aβ2-GPI. Optimal cutoffs and diagnostic performances of the research systems were established employing the LCA-derived gold standard.

RESULTS

With area under the curve results of 0.96 and 0.89 for the detection of aCL and aβ2-GPI, the research SPR assays discriminated well between antibody-positive and antibody-negative sera. Their sensitivities and specificities were comparable to the investigated commercial immunoassays.

CONCLUSIONS

SPR assays are a suitable tool for the detection of aCL and aβ2-GPI with diagnostic performances not different from currently available commercial tests. LCA enabled the calculation of sensitivities and specificities for aPL assays in absence of a reference standard.

A multicenter study to assess the reproducibility of antiphospholipid antibody results produced by an automated system

Essentials Inter-lab variation studies for antiphospholipid antibodies (aPL) with the same assay are lacking. We carried out an assessment of repeatability and reproducibility of an automated aPL assay. High intra-center repeatability for anticardiolipin and aβ2 GPI makes duplicate testing unnecessary. Inter-lab reproducibility was high except for aβ2GPI IgG.

SUMMARY

Background Inter-assay variability is a well-known problem in antiphospholipid antibody testing, because of the lack of standardization. Inter-laboratory reproducibility for the same assay is similarly important. Objectives Testing repeatability and reproducibility of HemosIL® AcuStar for anticardiolipin (aCL) and antiβ2-glycoprotein I antibodies (aβ2GPI) IgG and IgM. Patients/Methods In this observational study, out of 420 samples from the thrombophilia centers of Ghent and Geneva, 100 samples were randomly selected and successively analyzed in three centers: Ghent (C1, in duplicate for repeatability evaluation), Geneva (C2) and Frankfurt (C3). Results Results from 99 samples were available, including 25 from patients with antiphospholipid syndrome (APS) and 74 from non-APS patients. The intra-center repeatability expressed as intra-class correlation coefficient (ICC) was higher than 0.99 for each parameter. Differences between two measurements rarely exceeded 1 U mL-1 for values below 100 U mL-1 , except for aβ2GPI IgG, where differences varied from -4 to 4 U mL-1 . The inter-center ICCs were higher than 0.99, except for aCL IgM (ICC = 0.961). These ICCs remained high even when considering values below 100 U mL-1 (0.943, 0.964 and 0.977 for aCL IgG, aCL gM and aβ2GPI IgM, respectively), except for aβ2GPI IgG (ICC = 0.652). Qualitative comparison showed less than 5% discordant classification between centers, with somewhat more discordant results for aβ2GPI IgG. Conclusions In terms of discriminating properties, the HemosIL® AcuStar has excellent intra-center repeatability and a good inter-center reproducibility for aCL IgG, aCL IgM and aβ2GPI IgM. Some concern may arise for aβ2GPI IgG.

A unique antiphospholipid assay recognizing phospholipid mixture compared with criteria antiphospholipid immunoassays in lupus patients

Background While essential for the classification of antiphospholipid syndrome (APS), anticardiolipin (aCL) assays lack specificity and anti-β2glycoproteinI (anti-β2GPI) assays lack sensitivity in this regard. Our aim was to perform a comparative analysis of the APhL ELISA assay (IgG/IgM) and criteria antiphospholipid (aPL) immunoassays in identifying APS-related clinical manifestations in a large group of patients with systemic lupus erythematosus (SLE). Methods Serum samples from 1178 patients from the Hopkins ( n = 543), LUMINA ( n = 588) and Jamaican SLE cohorts ( n = 47) were examined for IgG/IgM positivity in aCL (in-house), anti-β2GPI (two commercial kits) and APhL (Louisville APL) ELISA assays. Correlation of assay positivity with clinical manifestations and sensitivity, specificity, positive and negative predictive values and likelihood ratios were evaluated. A case series analysis was also performed in patients for whom there was isolated positivity in the specific aPL assays. Results The prevalence of aCL positivity was 34.9%, anti-β2GPI kit A was 22.6%, APhL was 11.5% and anti-β2GPI kit B was 7.6% in the study population. Anti-β2GPI kit B, aCL and APhL assays were correlated with venous thrombosis, while only APhL was significantly correlated with arterial thrombosis and consistently correlated with pregnancy-related morbidity. No significant correlations were noted for anti-β2GPI kit A. Sensitivity was greatest for aCL assays followed by anti-β2GPI kit A, APhL and anti-β2GPI kit B, while specificity was greatest and equal for anti-β2GPI kit B and APhL assays. Conclusions Overall, APhL antibodies, especially IgG, represent a promising biomarker for the classification of APS patients in the context of autoimmunity and in risk assessment with regards to pregnancy morbidity and thrombotic manifestations.

Performance Characteristics of Commercial Immunoassays for the Detection of IgG and IgM Antibodies to β2 Glycoprotein I and an Initial Assessment of Newly Developed Reference Materials for Assay Calibration

OBJECTIVES

To investigate the performance characteristics and impact of newly developed reference calibrators on the commutability between anti-β2 glycoprotein I (anti-β2 GPI) immunoassays in antiphospholipid syndrome (APS) and/or systemic lupus erythematosus (SLE).

METHODS

Immunoglobulin G (IgG) and immunoglobulin M (IgM) anti-β2 GPI immunoassays from four manufacturers were evaluated. Serum samples from 269 patients (APS only, n = 31; SLE and APS, n = 83; SLE only, n = 129; pregnancy-related clinical manifestations without APS, n = 26) and 162 women with histories of successful pregnancies were tested. Results were expressed in kit-specific arbitrary units and in the calibrator reference units (RUs) based on 99th percentile cutoff values. Diagnostic accuracies, correlation between kits, and specific clinical manifestations in APS were investigated.

RESULTS

The sensitivities of the assays ranged from 15.8% to 27.2% (IgG) and 12.3% to 15.8% (IgM) while specificities ranged from 79.4% to 86.5% (IgG) and 80.6% to 84.5% (IgM). There was moderate to almost perfect interassay reliability (Cohen κ, 0.69-0.98), and Spearman correlation coefficients were generally improved when results of the IgG determinations were expressed in RUs.

CONCLUSIONS

Although qualitative agreements between immunoassays for both antibody isotypes are acceptable, correlations with APS clinical manifestations were kit dependent. Only the use of IgG reference material improved quantitative correlations between assays.

The role of anti-phospholipid antibodies in autoimmune reproductive failure

Anti-phospholipid antibodies (aPL) are autoantibodies that are associated with thrombosis and a range of pregnancy complications including recurrent pregnancy loss and pre-eclampsia. The three clinically relevant, well-characterized aPL are anti-cardiolipin antibodies, lupus anticoagulant and anti-beta-2-glycoprotein I (β2GPI) antibodies. aPL do not bind directly to phospholipids but instead bind to a plasma-binding ‘cofactor’. The most extensively studied cofactor is β2GPI, whose role in pregnancy is not fully elucidated. Although the pathogenicity of aPL in recurrent pregnancy loss is well established in humans and animal models, the association of aPL with infertility does not appear to be causative. aPL may exert their detrimental effects during pregnancy by directly binding trophoblast cells of the placenta, altering trophoblast signalling, proliferation, invasion and secretion of hormones and cytokines, and by increasing apoptosis. Heparin is commonly used to treat pregnant women with aPL; however, as thrombotic events do not occur in the placentae of all women with aPL, it may exert a protective effect by preventing the binding of aPL to β2GPI or by acting through non-thrombotic pathways. The aim of this review is to present evidence summarizing the current understanding of this field.

Detection of autoantibodies using chemiluminescence technologies

Context: Although autoantibody detection methods such as indirect immunofluorescence (IIF) and enzyme-linked immunosorbent assays (ELISAs) have been available for many years and are still in use the innovation of fast, fully automated instruments using chemiluminescence technology in recent years has led to rapid adoption in autoimmune disease diagnostics. In 2009, BIO-FLASH, a fully automated, random access chemiluminescent analyzer, was introduced, proceeded by the development of the QUANTA Flash chemiluminescent immunoassays (CIA) for autoimmune diagnostics.

Objective: To summarize the evolution of CIAs for the detection of autoantibodies and to review their performance characteristics.

Methods: Pubmed was screened for publications evaluating novel QUANTA Flash assays and how they compare to traditional methods for the detection of autoantibodies. In addition, comparative studies presented at scientific meetings were summarized.

Results: Several studies were identified that compared the novel CIAs with conventional methods for autoantibody detection. The agreements ranged from moderate to excellent depending on the assay. The studies show how the CIA technology has enhanced the analytical and clinical performance characteristics of many autoantibody assays supporting both diagnosis and follow-up testing.

Conclusion: CIA has started to improve the diagnostic testing of autoantibodies as an aid in the diagnosis of a broad range of autoimmune diseases.

Evaluation of the Clinical Performance of a Novel Chemiluminescent Immunoassay for Detection of Anticardiolipin and Anti-Beta2-Glycoprotein 1 Antibodies in the Diagnosis of Antiphospholipid Syndrome

Detection of antiphospholipid antibodies represents the first-line approach for diagnosis of antiphospholipid syndrome (APS). In this study, we evaluated the clinical performance of a novel chemiluminescence assay (CIA) in detection of IgG/IgM/IgA anti-cardiolipin (aCL) and IgG/IgM/IgA anti-β2 glycoprotein 1 (aβ2GP1) antibodies and to compare it with commercial enzyme-linked immunosorbent assay (ELISA) kits from the same manufacturer.A total of 227 sera were tested in this study, including 84 samples from patients with APS, 104 samples from patients with non-APS diseases as disease controls, and 39 healthy controls. Serum IgG/IgM/IgA aCL and IgG/IgM/IgA aβ2GP1 were determined by both ELISA (QUANTA Lite™ ELISA) and CIA (QUANTA Flash®assays).Significant quantitative correlations were identified between ELISA and CIA in IgG/IgM/IgA aCL and IgG/IgM/IgA aβ2GP1 autoantibodies detection (P < 0.001), with the rho value ranging from 0.51 to 0.87. In addition, ELISA and CIA demonstrated good qualitative agreements in IgG/IgM/IgA aCL and IgM/IgA aβ2GP1 autoantibodies determination with kappa coefficient ranged from 0.52 to 0.77. In contrast, ELISA and CIA showed a moderate qualitative agreement in IgG aβ2GP1 detection with a kappa value of 0.2. Notably, significantly higher IgG aβ2GP1 positive sera were detected by CIA, compared to those detected by ELISA in both primary APS (52.9% vs. 8.8%) and APS associated to other diseases sera (70.0% vs. 8.0%). For diagnosis of APS, IgG aβ2GP1 detection by CIA (IgG aβ2GP1 CIA) demonstrated the highest sensitivity (63.1%), followed by IgG aCL CIA (48.8%). More importantly, IgG aβ2GP1 CIA demonstrated the highest ability to predict the thrombotic events in patients with APS, with an OR of 3 (95% CI: 1.1-7.9).Our data suggest that this novel CIA assay had good performance in detecting aCL and aβ2GP1 antibodies, especially in the detection of IgG aβ2GP1 antibodies. Our findings could shed insight on the application of CIA in the laboratory diagnosis of APS in China.

Antiphospholipid syndrome and the relevance of antibodies to negatively charged phospholipids in diagnostic evaluation

The presence of lupus anticoagulant, moderate-to-high levels of IgG and/or IgM antibodies to beta-2 glycoprotein I or cardiolipin in association with at least one of the two major clinical manifestations (thrombosis and/or pregnancy-related morbidity) are required for a diagnosis of definite antiphospholipid syndrome (APS). The realization that certain negatively charged phospholipid (PL) autoantibodies broadly react with antibodies directed against cardiolipin and may be more reliable and specific markers for APS has led to the search for diagnostic assays with greater predictability for disease evaluation and management. This review focuses on the state-of-the-art analytical and clinical performance of IgG and IgM antibodies directed against negatively charged PLs, specifically phosphatidic acid (aPA), phosphatidylinositol (aPI), and phosphatidylserine (aPS), as well as the APhL assay, which contains a proprietary mixture of phospholipid antigens.

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.

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.

Lupus anticoagulant-hypoprothrombinemia syndrome: report of two cases and review of the literature

Lupus anticoagulant-hypoprothrombinemia syndrome (LA-HPS) is a rare acquired disorder caused by prothrombin antibodies. The disease is most common in the pediatric age group (<16 years), and more prevalent in women. There are well-established clinical diseases associated with LA-HPS, most notably systemic lupus erythematosus (SLE) and viral infections. The clinical manifestation of LA-HPS varies greatly in severity and it may cause severe life-threatening bleeding diathesis. LA-HPS is to be suspected when a patient presents with bleeding and a prolonged activated partial thromboplastin and prothrombin time, in combination with a lupus anticoagulant. The diagnosis is confirmed in the laboratory by identification of reduced prothrombin levels. There are no standardized recommendations for treatment of the hemorrhage associated with the syndrome; corticosteroids are used as first-line treatment. This review summarizes what is currently known about the pathogenesis, clinical features, diagnosis, treatment and prognosis of LA-HPS, and presents two case reports.

Multiple antiphospholipid antibodies positivity and antiphospholipid syndrome criteria re-evaluation

The antiphospholipid syndrome (APS) is characterized by the presence of aPL and thrombosis and/or pregnancy morbidity. The last APS laboratory classification criteria include the presence of at least one of the antiphospholipid antibodies (aPL) [lupus anticoagulant (LA), anticardiolipin (aCL) and/or anti-β2 glycoprotein I antibodies (aβ2GPI)] and introduced the concept of subclassification of APS patients into two different categories of aPL assay positivity (combination or single aPL). Several studies have recently shown that the risk for thrombosis increases with each additional aPL detected. We found that the presence of IgG antibodies to β2GPI and/or prothrombin increased thrombotic risk in patients with LA and/or aCLin a prospective study. Various studies have recently demonstrated that patients with triple positivity (LA, aCL and aβ2GPI) are at the highest risk for venous and arterial thrombosis and for obstetric complications. In retrospective but also in prospective studies the rate of thrombotic recurrence was high in subjects with triple positivity even while on anticoagulant therapy. In addition, the occurrence of a first thrombotic event in asymptomatic carriers of triple positivity was higher than in those with single aPL positivity. The inclusion of the detection of antibodies against domain I of β2GPI and/or antibodies to prothrombin would probably help to further identify more clinically relevant aPL. Based on the last findings, there are some proposals to consider only patients with triple positivity as definite APS (thrombotic and obstetric).