Antiphospholipid antibody testing for the antiphospholipid syndrome: a comprehensive practical review including a synopsis of challenges and recent guidelines

Variable Performance of Lupus Anticoagulant Testing: The Australasian/Asia-Pacific Experience

Lupus anticoagulant (LA) is one of three tests identified as laboratory criteria for definite antiphospholipid syndrome (APS). The other two tests are anticardiolipin antibody (aCL) and anti-β2-glycoprotein I (aβ2GPI) antibody. The presence of LA is assessed using clot-based tests, while the presence of aCL and aβ2GPI is assessed by immunological assays. Since no test can be considered 100% sensitive or specific for LA, current guidelines recommend using two different clot-based assays reflecting different principles, with the dilute Russell viper venom time (dRVVT) and activated partial thromboplastin time (aPTT) recommended. Initially, LA-sensitive reagents are used to screen for LA, and then, in "screen-positive" samples, LA-"insensitive" reagents are used to confirm LA. Because LA assays are based on clot detection, anything that can interfere with fibrin clot development may affect test results. In particular, in addition to LA, the tests are also sensitive to the presence of a wide range of clinical anticoagulants, reflecting preanalytical issues for testing. We provide updated findings for LA testing in our geographic region, using recent data from the Royal College of Pathologists of Australasia Quality Assurance Programs, an international external quality assessment program with approximately 120 participants. Data show a wide variety of assays in use, especially for aPTT testing, and variable outcomes in reported numerical values with these assays when assessing proficiency samples. dRVVT testing mostly comprised reagents from three main manufacturing suppliers, which also showed differences in numerical values for the same homogeneous tested samples. Nevertheless, despite the use of different test reagents and processes, >98% of participants correctly identified LA-negative samples as LA-negative and LA-positive samples as LA positive. We hope our findings, reflecting on the heterogeneity of test processes and test data, help improve diagnostic testing for LA in the future.

Association of Anti-Annexin A5 Antibody With Pregnancy Outcomes: A Cohort Study: Anti-annexin A5 antibody with pregnancy outcomes

OBJECTIVE

This study aims to evaluate the correlation between anti-annexin A5 (aANXA5) antibody in the blood and pregnancy outcomes .

METHODS

This study is a retrospective cohort study based on singleton pregnancies of the Third Affiliated Hospital of Wenzhou Medical University from May 2018 to December 2022. Baseline characteristics were collected from all participants. Logistic regression and interaction effect analyses were utilized to examine the risk impact of aANXA5 on pregnancy complications, adjusting for age, BMI, abortion, ANA, and aCL. Restricted cubic spline (RCS) and threshold effect analysis were applied to explore the relationship between aANXA5 levels and preterm birth (PTB), as well as pregnancy-induced hypertension (PIH).

RESULTS

The study included 501 participants, with 51 (10.2%) testing positive for aANXA5 and 450 (89.8%) testing negative. The aANXA5 positive group exhibited higher rates of ANA and antibodies to thyroglobulin (TGAb), along with increased incidences of PTB and PIH. Positive aANXA5 status was independently linked to an elevated risk of PTB (OR: 2.53, 95% CI: 1.30-4.94) and PIH (OR: 4.23, 95% CI: 1.54-11.62). Subsequent subgroup analysis indicated no significant interaction between the groups (p > 0.05). Threshold analysis revealed that the OR for PTB was 1.20 (95% CI: 1.03-1.39) in participants with aANXA5 levels ≥ 32.77 ng/mL, and the OR for PIH was 1.62 (95% CI: 1.15-2.28) in those with aANXA5 levels ≥ 33.20 ng/mL.

CONCLUSION

AANXA5 is independently associated with an increased risk of PTB and PIH. The identified optimal predictive cutoff values are 32.77 ng/mL for PTB and 33.20 ng/mL for PIH.

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.

Effects of Bushen Huoxue on integrin β3 and integrin β5 in the placental tissue of mice with repeated implantation failure caused by phospholipid antibodies

BACKGROUND

This study aimed to investigate the effects of the Kidney-Tonifying and Blood-Activating Formula on combating the downregulation of integrin β3 and integrin β5 in mouse placental tissue induced by phospholipid antibodies.

OBJECTIVE

This study aimed to investigate the effects of kidney-tonifying and blood-activating formulations on combating the downregulation of integrin β3 and integrin β5 in mouse placental tissue induced by phospholipid antibodies.

METHODS

Mice in the phospholipid antibody group and phospholipid antibody + kidney-tonifying and blood-activating formula group underwent repeated implantation experiments, and the expression of integrin β3 and integrin β5 in placental tissue was observed. The effects of the kidney-tonifying and blood-activating formula on mouse placental tissue were evaluated through biochemical index tests, histopathological observations, and immunohistochemical staining.

RESULTS

After intervention with the kidney-tonifying and blood-activating formula, the expression of integrin β3 and integrin β5 in placental tissue was notably upregulated, and placental structure was restored. Kidney-Tonifying and Blood-Activating Formula significantly improved abnormal biochemical indices and exerted a remarkable protective effect on placental tissue pathology.

CONCLUSION

The kidney-tonifying and blood-activating formula effectively counteracted the downregulation of integrin β3 and integrin β5 in mouse placental tissue induced by phospholipid antibodies and alleviated placental tissue pathology through structural improvement and protection. Therefore, kidney-tonifying and blood-activating formulas may serve as potential therapeutic agents for recurrent implantation failure, offering new insights and approaches for clinical treatment.

Clinical and Laboratory Diagnosis of Antiphospholipid Syndrome: A Review

The antiphospholipid syndrome (APS) manifests through venous or arterial thrombosis, with or without pregnancy complication alongside the continuous presence of antiphospholipid antibodies (aPL). APS classification relies on three aPL subtypes: anticardiolipin (aCL), anti-β2-glycoprotein I antibodies (anti-β2GPI), and lupus anticoagulants (LA) antibodies. Given that thrombosis and pregnancy issues are not unique to APS, the precise and reliable identification of aPL forms the basis for diagnosis. Semi-quantitative solid-phase assays identify two antibodies, aCL and anti-β2GPI, while LA detection occurs through various phospholipid-dependent coagulation assays that are based on antibody behaviour. LA, specifically, is conclusively associated with thrombosis, prompting discussions around the serological criteria for APS. Despite advancements in LA detection, the standardisation of all aPL detection assays remains imperative. The combined presence of aCL and anti-β2GPI with thrombosis inconsistently triggers concern. Initial presentations by APS patients commonly exhibit a heightened risk of stroke, miscarriages in the later stages of pregnancy, positive results of LA tests, and widespread thrombosis across multiple organs, often leading to adverse outcomes. Correctly diagnosing this condition is pivotal to avoid unnecessary long-term secondary thromboprophylaxis.

Insight into antiphospholipid syndrome: the role and clinical utility of neutrophils extracellular traps formation

Antiphospholipid syndrome (APLS) is a systemic immune dysregulation distinguished by repetitive complications and pregnancy loss in the absence of definite etiology. Most research focuses on the laboratory detection and clinical features of APLS, but its precise etiology remains to be deeply explored. NETosis is a newly developed theory in the pathophysiology of APLS which may serve as the missing bridge between coagulation and inflammation reaching the disease progression and severity. We aimed in this study to navigate the prognostic role of NETosis in thrombotic APLS. Our study included 49 newly diagnosed APLS patients (both 1ry and 2ry) who met clinical and laboratory criteria as per the international consensus statement on the update of the classification criteria for definite APLS and were sub-classified according to the occurrence of thrombotic events in thrombotic and non-thrombotic types. In addition, 20 sex and age-matched reactive subjects and 20 sex and age-matched healthy volunteer controls were enrolled. NETosis formation was assessed by measuring serum Myeloperoxidase (MPO) and Histones level using the enzyme-linked immunosorbent assay (ELISA) technique. Both MPO and Histones levels were able to discriminate among APLS cases from normal controls, showing significant cutoffs of > 2.09 ng/ml for MPO and > 1.45 ng/ml for Histones (AUC values were 0.987and 1.000, respectively). These values can be used as predictors for NETosis pathophysiology in APLS patients. Additionally, these markers demonstrated a significant association with several prognostic indicators, including thrombosis, higher PT and INR, and lower hemoglobin (Hb) levels which are supposed to be ameliorated by using NETs inhibitors. In conclusion, we suggest that measuring NETosis markers, MPO, and Histones, in the early course of APLS using proposed cutoff values will facilitate the timely initiation of anti-NETosis therapy and improve the overall prognosis, particularly for patients with thrombotic APLS.

Insight into antiphospholipid syndrome: the role and clinical utility of neutrophils extracellular traps formation

Antiphospholipid syndrome (APLS) is a systemic immune dysregulation distinguished by repetitive complications and pregnancy loss in the absence of definite etiology. Most research focuses on the laboratory detection and clinical features of APLS, but its precise etiology remains to be deeply explored. NETosis is a newly developed theory in the pathophysiology of APLS which may serve as the missing bridge between coagulation and inflammation reaching the disease progression and severity. We aimed in this study to navigate the prognostic role of NETosis in thrombotic APLS. Our study included 49 newly diagnosed APLS patients (both 1ry and 2ry) who met clinical and laboratory criteria as per the international consensus statement on the update of the classification criteria for definite APLS and were sub-classified according to the occurrence of thrombotic events in thrombotic and non-thrombotic types. In addition, 20 sex and age-matched reactive subjects and 20 sex and age-matched healthy volunteer controls were enrolled. NETosis formation was assessed by measuring serum Myeloperoxidase (MPO) and Histones level using the enzyme-linked immunosorbent assay (ELISA) technique. Both MPO and Histones levels were able to discriminate among APLS cases from normal controls, showing significant cutoffs of > 2.09 ng/ml for MPO and > 1.45 ng/ml for Histones (AUC values were 0.987and 1.000, respectively). These values can be used as predictors for NETosis pathophysiology in APLS patients. Additionally, these markers demonstrated a significant association with several prognostic indicators, including thrombosis, higher PT and INR, and lower hemoglobin (Hb) levels which are supposed to be ameliorated by using NETs inhibitors. In conclusion, we suggest that measuring NETosis markers, MPO, and Histones, in the early course of APLS using proposed cutoff values will facilitate the timely initiation of anti-NETosis therapy and improve the overall prognosis, particularly for patients with thrombotic APLS.

Antiphospholipid Antibody Testing: An Audit on Testing Practices in a Public Tertiary Care Center

BACKGROUND

Antiphospholipid antibodies (aPLs) are antibodies directed against cell membrane components and can be associated with clinical features or be asymptomatic. Testing and interpreting these antibodies is associated with many challenges and pitfalls in clinical practice.

OBJECTIVE

To review all antiphospholipid antibody testing and describe the testing practices, indications for testing and interpretation of results to infer local challenges with aPL testing and subsequently address ways to overcome those challenges.

METHODS

This is a retrospective analysis of all aPL testing done in a tertiary center between 2014 and 2018. Characteristics of study patients collected through chart review were described using the mean and standard deviation for continuous variables and proportion for categorical variables. Group differences were compared between patients with any aPL-positive result and those with no positive result using chi-square or Fisher's exact test as appropriate for categorical variables and a simple regression model for numerical variables.

RESULTS

Among 414 patients undergoing aPL testing, mainly adult females, 62 (14.9%) patients had at least one positive antibody, of those, 26 (42%) had repeat testing done. Testing was mostly done for obstetric indication (107, 25.8%), with 36 patients having one or two early pregnancy losses <10 weeks as their testing indication. A total of 27 (6.5%) patients were labeled with APS/possible APS based on chart review, but on review of the testing of those patients according to classification criteria, only nine patients satisfied the criteria for APS.

CONCLUSION

This study highlights the clinical challenges associated with aPL testing, including the controversies around indication for testing, the low rates of repeat testing to confirm persistence, and the common misinterpretation of results. Having an aPL testing profile, explicit reference ranges, results commentary, and close interaction between ordering physicians and laboratory staff might be starting points to overcome these challenges.

Is a Higher Body Mass Index a Risk Factor for Developing Antiphospholipid Antibody Syndrome?

BACKGROUND

 Antiphospholipid antibodies (aPLs) are antibodies directed against components of the cell membrane and can be associated with clinical features or be asymptomatic in 1-5% of the population.

OBJECTIVE

The objective of this study is to investigate the frequency of aPL positivity based on body mass index (BMI).

METHODS

 This is a retrospective analysis of all aPL testing done in a tertiary center between 2010 and 2020. The difference between patients with BMI <25, BMI 25-30, and BMI>30 is calculated using chi-square or Fisher's exact test as appropriate for categorical variables and a two-sample t-test for numerical variables. Unadjusted then multivariable logistic regression models were conducted to evaluate the effect of BMI on aPL positivity adjusting for age, thrombosis history, pregnancy complications history, and presence of autoimmune disease. Sex was included as an effect modifier.

RESULTS

 Among 312 patients, the outcome (any positive aPL) was detected in 26 (20.8%), 13 (13.0%), and 16 (18.4%) patients with BMI groups: BMI <25, BMI 25-30, and BMI > 30, respectively. A multivariable logistic regression showed that those with BMI 25-30 had a lower risk of aPL positivity when compared to patients with BMI <25 (OR of 0.55 CI 0.25 - 1.14, p=0.116), and patients with BMI >30 also carried a lower risk compared with patients with BMI<25 (OR of 0.76, 95% CI 0.36 - 1.56, p=0.46); these results were not statistically significant.

INTERPRETATION

 The results suggest that a higher BMI was not a risk factor for aPL positivity. A better understanding of the complex interactions between antiphospholipid antibodies and obesity should be further investigated.

Antiphospholipid Antibody Testing for Anti-cardiolipin and Anti-β2 Glycoprotein I Antibodies Using Chemiluminescence-Based Panels

Antiphospholipid (antibody) syndrome (APS) is a prothrombotic condition with increased risk for thrombosis and pregnancy-related morbidity. In addition to clinical criteria related to these risks, APS is characterized by the persistent presence of antiphospholipid antibodies (aPL), as detected in the laboratory using a potentially wide variety of assays. The three APS criteria-related assays are lupus anticoagulant (LA), as detected using clot-based assays, and the solid-phase assays of anti-cardiolipin antibodies (aCL) and anti-β2 glycoprotein I antibodies (aβ2GPI), with immunoglobulin subclasses of IgG and/or IgM. These tests may also be used for the diagnosis of systemic lupus erythematosus (SLE). In particular, APS diagnosis/exclusion remains challenging for clinicians and laboratories because of the heterogeneity of clinical presentations in those being evaluated and the technical application and variety of the associated tests used in laboratories. Although LA testing is affected by a wide variety of anticoagulants, which are often given to APS patients to prevent any associated clinical morbidity, detection of solid-phase aPL is not influenced by these anticoagulants, and this thus represents a potential advantage to their application. On the other hand, various technical issues challenge accurate laboratory detection or exclusion of aPL. This report describes protocols for the assessment of solid-phase aPL, specifically aCL and aβ2GPI of IgG and IgM class by means of a chemiluminescence-based assay panel. These protocols reflect tests able to be performed on the AcuStar instrument (Werfen/Instrumentation Laboratory). Certain regional approvals may also allow this testing to be performed on a BIO-FLASH instrument (Werfen/Instrumentation Laboratory).

Hemostasis and Thrombosis: An Overview Focusing on Associated Laboratory Testing to Diagnose and Help Manage Related Disorders

Hemostasis is a complex but balanced process that permit normal blood flow, without adverse events. Disruption of the balance may lead to bleeding or thrombotic events, and clinical interventions may be required. Hemostasis laboratories typically offer an array of tests, including routine coagulation and specialized hemostasis assays used to guide clinicians for diagnosing and managing patients. Routine assays may be used to screen patients for hemostasis-related disturbances but may also be used for drug monitoring, measuring efficacy of replacement or adjunctive therapy, and other indications, which may then be used to guide further patient management. Similarly, "specialized" assays are used for diagnostic purposes or may be used to monitor or measure efficacy of a given therapy. This chapter provides an overview of hemostasis and thrombosis, with a focus on laboratory testing that may be used to diagnose and help manage patients suspected of hemostasis- and thrombosis-related disorders.

An Overview of Laboratory Testing for Antiphospholipid Antibodies

Antiphospholipid antibodies (aPL) represent a group of autoantibodies directed against phospholipids. These antibodies may arise in a number of autoimmune conditions, of which the antiphospholipid (antibody) syndrome (APS) is best recognized. aPL can be detected by various laboratory assays, essentially comprising both solid-phase (immunological) assays and "liquid-phase" clotting assays identifying so-called lupus anticoagulants (LA). aPL are associated with various adverse pathologies, including thrombosis and placental/fetal morbidity and mortality. The type of aPL present, as well as the pattern of reactivity, is variously associated with the severity of the pathology. Thus, laboratory testing for aPL is indicated to help assess the future risk of such events, as well as representing certain "classification" criteria for APS, also used as surrogates for diagnostic criteria. The current chapter overviews the laboratory tests available to measure aPL and their potential clinical utility.

A multi-laboratory assessment of lupus anticoagulant assays performed on the ACL TOP 50 family for harmonized testing in a large laboratory network

Introduction

Lupus anticoagulant (LA) testing is commonly performed within hemostasis laboratories, and the ACL TOP 50 family of instruments represent a new “single platform” of hemostasis instrumentation. Our aim was to evaluate these instruments and manufacturer reagents or alternatives for utility in LA testing.

Methods

Comparative evaluations of LA testing using newly installed ACL TOPs 550 and 750 as well as comparative assessments with existing “reference,” predominantly Stago, instrumentation, and reagents. Evaluations comprised both dilute Russell viper venom time (dRVVT) and activated partial thromboplastin time (APTT)‐based assays. Establishment of normal reference ranges (NRR).

Results

The HemosIL dRVVT‐based assays showed good comparability with the existing Stago reference method (R > 0.9) and could be considered as verified as fit for purpose. A variety of APTT assays was additionally evaluated for LA utility, and we identified from the assessment good utility of a non‐Werfen solution in Hyphen BioMed Cephen reagents. NRR were established based on ≥120 normal individual plasma samples.

Conclusion

This evaluation of LA reagents on ACL TOP 50 Family instruments identified overall acceptable performance of both dRVVT (Werfen solution) and APTT (non‐Werfen solution) to enable harmonization of LA testing in our large network.

Lupus anticoagulant testing during anticoagulation, including direct oral anticoagulants

Background

Lupus anticoagulants (LA) are one laboratory criterion for classification of antiphospholipid syndrome, with presence of vascular thrombosis and/or pregnancy/fetal morbidity being clinical criteria. The presence of LA is detected (or excluded) by laboratory testing, with the activated partial thromboplastin time and dilute Russell's viper venom time the most commonly used tests. Given the association of thrombosis with LA, it is no surprise that anticoagulants are used to treat or manage such patients.

Objectives

To review and discuss interferences from anticoagulants on LA testing, and strategies to mitigate these.

Methods

This narrative review assessed interference from commonly used anticoagulants, focusing on LA testing while on direct oral anticoagulants (DOACs), including use of DOAC neutralizers.

Results

The classical anticoagulants comprise vitamin K antagonists such as warfarin, and heparins, predominantly unfractionated heparin and low molecular weight heparin (LMWH). DOACs have emerged with favorable efficacy and safety. These comprise two classes: direct anti-thrombin (anti-IIa; dabigatran) or direct anti-Xa (rivaroxaban, apixaban, edoxaban) agents. All anticoagulants affect clotting assays, although there are differences in effects according to anticoagulant and assay. Nevertheless, because of such interferences, anticoagulants can lead to false-negative or false-positive LA findings. Several strategies can mitigate such interferences, including avoidance of testing while patients are on such anticoagulants, temporarily switching to an anticoagulant (i.e., LMWH) with less assay interference, testing for LA at nadir levels of anticoagulants, and/or use of anticoagulant neutralizers.

Conclusion

Whilst the best approach is to avoid LA testing on patients taking anticoagulants; if unavoidable, testing may be facilitated by various mitigating strategies.

Antiphospholipid antibodies in COVID-19-associated pneumonia patients in intensive care unit

OBJECTIVES

Antiphospholipid antibodies (APAs) increase the risk of excessive blood clotting, but their role in COVID-19 remains unclear. We aimed to investigate the presence of conventional APAs used in the classification of antiphospholipid antibody syndrome in patients with severe lung infection with SARS-CoV-2 and to compare these results with non-COVID-19 critically ill patients.

METHODS

Thirty-one COVID-19 patients (COVID group) and 28 non-COVID-19 critically ill patients (non-COVID group), were included in the study. Anti-cardiolipin (ACA) (IgG, IgM), anti-β2-glycoprotein 1 (Anti-β2GPI) (IgG, IgM, and IgA), and if the patient had not received any anti thrombotic agent before blood collection, lupus anticoagulant (LAC) tests were studied from the plasma of the patients. For testing ACA and Anti-β2GPI, ELISA method was used, while fully automated coagulometer device was used for LAC test.

RESULTS

APAs were positive in 25.81% in the COVID group (8/31) and 25% in the non-COVID group (7/28). LAC was the most common APA present in 23.08% of the COVID-19 group, who underwent measurement (6/26), while 3.57% of the non-COVID group was LAC positive (1/28) (p = .047). In the COVID group, ACA IgM, and IgG were positive in 6.45% and 0%, respectively (2/31 vs 0/31). In the non-COVID group, ACA IgM was not positive in any patient, while ACA IgG was positive in 7.14% (2/28). Anti-β2GPI IgG and IgM tests were not positive in any patient in either the COVID or the non-COVID group. Anti-β2GPI IgA were positive in 6.45% and 14.29%, respectively (2/31 vs 4/28).

CONCLUSION

In this study, APAs were equally positive in critically ill patients among COVID-19 or non-COVID-19 patients. Only LAC was more observed in COVID-19 patients.

KEY MESSAGES

Bioactive Molecules Derived from Snake Venoms with Therapeutic Potential for the Treatment of Thrombo-Cardiovascular Disorders Associated with COVID-19

As expected, several new variants of Severe Acute Respiratory Syndrome-CoronaVirus-2 (SARS-CoV-2) emerged and have been detected around the world throughout this Coronavirus Disease of 2019 (COVID-19) pandemic. Currently, there is no specific developed drug against COVID-19 and the challenge of developing effective antiviral strategies based on natural agents with different mechanisms of action becomes an urgent need and requires identification of genetic differences among variants. Such data is used to improve therapeutics to combat SARS-CoV-2 variants. Nature is known to offer many biotherapeutics from animal venoms, algae and plant that have been historically used in traditional medicine. Among these bioresources, snake venom displays many bioactivities of interest such as antiviral, antiplatelet, antithrombotic, anti-inflammatory, antimicrobial and antitumoral. COVID-19 is a viral respiratory sickness due to SARS-CoV-2 which induces thrombotic disorders due to cytokine storm, platelet hyperactivation and endothelial dysfunction. This review aims to: (1) present an overview on the infection, the developed thrombo-inflammatory responses and mechanisms of induced thrombosis of COVID-19 compared to other similar pathogenesis; (2) underline the role of natural compounds such as anticoagulant, antiplatelet and thrombolytic agents; (3) investigate the management of coagulopathy related to COVID-19 and provide insight on therapeutic such as venom compounds. We also summarize the updated advances on antiviral proteins and peptides derived from snake venoms that could weaken coagulopathy characterizing COVID-19.

Is Lupus Anticoagulant a Significant Feature of COVID-19? A Critical Appraisal of the Literature

The term "lupus anticoagulant (LA)" identifies a form of antiphospholipid antibodies (aPLs) causing prolongation of clotting tests in a phospholipid concentration-dependent manner. LA is one of the laboratory criteria identified in patients with antiphospholipid (antibody) syndrome (APS). The presence of LA in patients with APS represents a significant risk factor for both thrombosis and pregnancy morbidity. There have been several reports of similarities between some of the pathophysiological features of COVID-19 and APS, in particular the most severe form, catastrophic APS. There have also been many reports identifying various aPLs, including LA, in COVID-19 patients. Accordingly, a very pertinent question arises: "Is LA a feature of COVID-19 pathology?" In this review, we critically appraise the literature to help answer this question. We conclude that LA positivity is a feature of COVID-19, at least in some patients, and potentially those who are the sickest or have the most severe infection. However, many publications have failed to appropriately consider the many confounders to LA identification, being assessed using clot-based assays such as the dilute Russell viper venom time, the activated partial thromboplastin time (aPTT), and the silica clotting time. First, most patients hospitalized with COVID-19 are placed on anticoagulant therapy, and those with prior histories of thrombosis would possibly present to hospital already on anticoagulant therapy. All anticoagulants, including vitamin K antagonists, heparin (both unfractionated heparin and low-molecular-weight heparin), and direct oral anticoagulants affect these clot-based assays. Second, C-reactive protein (CRP) is highly elevated in COVID-19 patients, and also associated with severity. CRP can also lead to false-positive LA, particularly with the aPTT assay. Third, persistence of aPL positivity (including LA) is required to identify APS. Fourth, those at greatest risk of thrombosis due to aPL are those with highest titers or multiple positivity. Most publications either did not identify anticoagulation and/or CRP in their COVID-19 cohorts or did not seem to account for these as possible confounders for LA detection. Most publications did not assess for aPL persistence, and where persistence was checked, LA appeared to represent transient aPL. Finally, high titer aPL or multiple aPL positivity were in the minority of COVID-19 presentations. Thus, at least some of the reported LAs associated with COVID-19 are likely to be false positives, and the relationship between the detected aPL/LA and COVID-19-associated coagulopathy remains to be resolved using larger and better studies.

COVID-19 and Antiphospholipid Antibodies: Time for a Reality Check?

Antiphospholipid antibodies (aPL) comprise a panel of autoantibodies that reflect a potential prothrombotic risk in several autoimmune conditions, most notably antiphospholipid (antibody) syndrome (APS). aPL can be divided into those that form part of the laboratory criteria for APS, namely, lupus anticoagulant (LA), as well as anticardiolipin antibodies (aCL) and anti-β2-glycoprotein I antibodies (aβ2GPI) of the immunoglobulin G and M classes, and those that form a group considered as "noncriteria antibodies." The noncriteria antibodies include, for example, antiphosphatidylserine antibodies (aPS), antiprothrombin antibodies (aPT), and antiphosphatidylserine/prothrombin complex antibodies (aPS/PT). COVID-19 (coronavirus disease 2019) represents a prothrombotic disorder, and there have been several reports of various aPL being present in COVID-19 patients. There have also been similarities drawn between some of the pathophysiological features of COVID-19 and APS, in particular, the most severe form, catastrophic APS (CAPS). In this review, we critically appraise the literature on aPL and COVID-19. This is a companion piece to a separate review focused on LA. In the current review, we primarily concentrate on the so-called solid phase identifiable aPL, such as aCL and aβ2GPI, but also reflect on noncriteria aPL. We conclude that aPL positivity may be a feature of COVID-19, at least in some patients, but in general, identified "solid-phase" aPL are of low titer and not able to be well-linked to the thrombotic aspects of COVID-19. Also, most publications did not assess for aPL persistence, and where persistence was checked, the findings appeared to represent transient aPL. Importantly, high-titer aPL or multiple aPL positivity (including double, triple) were in the minority of COVID-19 presentations, and thus discount any widespread presence of APS, including the most severe form CAPS, in COVID-19 patients.

Mixing studies for lupus anticoagulant: mostly yes, sometimes no

Lupus anticoagulants (LAs) represent one manifestation of the clinical condition called antiphospholipid syndrome (APS) and are associated with many adverse clinical outcomes, but primarily with thrombosis and/or pregnancy morbidity. LAs are identified by laboratory testing, principally using clot-based assays based on Russell viper venom time (RVVT) and activated partial thromboplastin time (APTT) test methods. All three of the most recent guidance documents for LA testing recommend using these tests, although they vary in regard to inclusion/exclusion of other test processes. Mixing studies form part of the process of LA identification/exclusion, since in vitro LAs act like coagulation inhibitors. Mixing studies are also supported by all three LA guidance documents, but recommendations vary in regard to relative importance and placement in the LA identification/exclusion algorithm. This Point article takes the position that mixing tests are usually indicated for appropriate identification/exclusion of LAs, but can occasionally be omitted.

Molecular Mechanisms of "Antiphospholipid Antibodies" and Their Paradoxical Role in the Pathogenesis of "Seronegative APS"

Antiphospholipid Syndrome (APS) is an autoimmune disease characterized by arterial and/or venous thrombosis and/or pregnancy morbidity, associated with circulating antiphospholipid antibodies (aPL). In some cases, patients with a clinical profile indicative of APS (thrombosis, recurrent miscarriages or fetal loss), who are persistently negative for conventional laboratory diagnostic criteria, are classified as "seronegative" APS patients (SN-APS). Several findings suggest that aPL, which target phospholipids and/or phospholipid binding proteins, mainly β-glycoprotein I (β-GPI), may contribute to thrombotic diathesis by interfering with hemostasis. Despite the strong association between aPL and thrombosis, the exact pathogenic mechanisms underlying thrombotic events and pregnancy morbidity in APS have not yet been fully elucidated and multiple mechanisms may be involved. Furthermore, in many SN-APS patients, it is possible to demonstrate the presence of unconventional aPL ("non-criteria" aPL) or to detect aPL with alternative laboratory methods. These findings allowed the scientists to study the pathogenic mechanism of SN-APS. This review is focused on the evidence showing that these antibodies may play a functional role in the signal transduction pathway(s) leading to thrombosis and pregnancy morbidity in SN-APS. A better comprehension of the molecular mechanisms triggered by aPL may drive development of potential therapeutic strategies in APS patients.

From Animal Poisons and Venoms to Medicines: Achievements, Challenges and Perspectives in Drug Discovery

Animal poisons and venoms are comprised of different classes of molecules displaying wide-ranging pharmacological activities. This review aims to provide an in-depth view of toxin-based compounds from terrestrial and marine organisms used as diagnostic tools, experimental molecules to validate postulated therapeutic targets, drug libraries, prototypes for the design of drugs, cosmeceuticals, and therapeutic agents. However, making these molecules applicable requires extensive preclinical trials, with some applications also demanding clinical trials, in order to validate their molecular target, mechanism of action, effective dose, potential adverse effects, as well as other fundamental parameters. Here we go through the pitfalls for a toxin-based potential therapeutic drug to become eligible for clinical trials and marketing. The manuscript also presents an overview of the current picture for several molecules from different animal venoms and poisons (such as those from amphibians, cone snails, hymenopterans, scorpions, sea anemones, snakes, spiders, tetraodontiformes, bats, and shrews) that have been used in clinical trials. Advances and perspectives on the therapeutic potential of molecules from other underexploited animals, such as caterpillars and ticks, are also reported. The challenges faced during the lengthy and costly preclinical and clinical studies and how to overcome these hindrances are also discussed for that drug candidates going to the bedside. It covers most of the drugs developed using toxins, the molecules that have failed and those that are currently in clinical trials. The article presents a detailed overview of toxins that have been used as therapeutic agents, including their discovery, formulation, dosage, indications, main adverse effects, and pregnancy and breastfeeding prescription warnings. Toxins in diagnosis, as well as cosmeceuticals and atypical therapies (bee venom and leech therapies) are also reported. The level of cumulative and detailed information provided in this review may help pharmacists, physicians, biotechnologists, pharmacologists, and scientists interested in toxinology, drug discovery, and development of toxin-based products.

Coagulation mixing studies: Utility, algorithmic strategies and limitations for lupus anticoagulant testing or follow up of abnormal coagulation tests

Coagulation testing underpins the investigation of hemostasis and/or monitoring of anticoagulation therapy for prevention and/or treatment of thrombosis related pathology. Assessment of coagulation results requires comparison against a normal reference range or interval (NRR/NRI). Results flagged as "abnormal" (ie, above the NRR/NRI for patients not on anticoagulant therapy), typically require further evaluation. eg, follow up or reflexive testing is used to identify the reason for prolongation, especially when supported by clinical context (eg, bleeding). Mixing tests may have utility to help identify the pathway of follow-up testing (ie, towards investigation of factor deficiencies, or else inhibitors), and are also useful for investigation of lupus anticoagulants (LA). In general, mixing tests that "correct" tend to suggest the presence of factor deficiencies, where as those that do not correct suggest the presence of "inhibitors". Various approaches can be used to identify correction/non-correction, and all have strengths and limitations. Furthermore, eventual identification of causal factor deficiencies or even "inhibitors" may (eg, factor VIII or IX deficiencies or inhibitors) or may not (eg, factor XII deficiency) be clinically important. Ultimately, mixing studies performed in view of appropriate clinical scenarios (eg, bleeding patient) and for LA investigations in symptomatic patients will have best utility.

The Russell viper venom time (RVVT) test for investigation of lupus anticoagulant (LA)

Lupus anticoagulants (LAs) are a laboratory representation of the clinical syndrome of antiphospholipid syndrome (APS), and can also arise in other pathological states. Laboratory testing for LA is complex and three separate recent guidelines have been published. One test, the Russell viper venom time (RVVT), is the mandated laboratory test for inclusion in LA identification/exclusion in all three guidance documents. This is because the the RVVT is recognized to have great sensitivity for LA, with this generally recognized to be greater than that of most other LA screening assays. However, the RVVT is also very sensitive to the presence of many anticoagulant drugs, which diminishes its specificity for LA. Various strategies can be used to improve LA specificity and reduce anticoagulant assay interference.

Impact of different preanalytical conditions on results of lupus anticoagulant tests

INTRODUCTION

The currently recommended preanalytical conditions for lupus anticoagulant (LA) analysis require analyzing samples in fresh or freshly frozen platelet-poor plasma. The aim of this study was to evaluate whether alternative and less cumbersome preanalytical procedures for LA testing give significantly different results compared to recommended conditions.

MATERIALS AND METHODS

Citrated blood samples were drawn from 29 study participants, 15 with negative and 14 with positive LA results. The samples were processed according to the ISTH guideline for LA testing and compared to several alternative preanalytical conditions. Measurements were performed using the dilute Russell's viper venom time (DRVVT) and silica clotting time (SCT), both screen and confirm, on a STA-R Evolution analyzer. Stability criteria were based upon biological variation.

RESULTS

All DRVVT tests (normalized screen, confirm, and screen/confirm ratio) met the stability criteria for all the preanalytical conditions. The SCT tests (normalized screen, confirm, and screen/confirm ratio) met the stability criteria only when treated according to the ISTH guideline, except for SCT normalized screen/confirm ratio which also met the stability criteria for double-centrifuged aliquoted plasma stored in room temperature for 24 hours and then analyzed "fresh" or after being frozen. One warfarin-treated patient was reclassified from positive to negative for DRVVT after the preanalytical modifications, while 2 of 29 participants became falsely positive for 2 of 8 conditions for SCT.

CONCLUSIONS

The DRVVT assays met the criteria for stability for all preanalytical conditions tested, while the SCT assays should be interpreted with caution if the preanalytical guidelines from ISTH are not followed.

Evaluation of the sensitivity and specificity of a novel line immunoassay for the detection of criteria and non-criteria antiphospholipid antibodies in comparison to established ELISAs

Background

Persistent antiphospholipid antibodies (aPL) constitute the serological hallmark of the antiphospholipid syndrome (APS). Recently, various new assay technologies for the detection of aPL better suited to multiplex reaction environments than ELISAs emerged. We evaluated the diagnostic performance of such a novel line immunoassay (LIA) for the simultaneous detection of 10 different aPL.

Methods

Fifty-three APS patients and 34 healthy controls were investigated for criteria (antibodies against cardiolipin [aCL], β2-glycoprotein I [aβ2-GPI]) and non-criteria aPL (antibodies against phosphatidic acid [aPA], phosphatidyl-choline [aPC], -ethanolamine [aPE], -glycerol [aPG], -inositol [aPI], -serine [aPS], annexin V [aAnnV], prothrombin [aPT]) IgG and IgM by LIA. Criteria aPL were additionally determined with the established Alegria (ALE), AcuStar (ACU), UniCap (UNI), and AESKULISA (AES) systems and non-criteria aPL with the AES system. Diagnostic performance was evaluated with a gold standard for criteria aPL derived from the results of the four established assays via latent class analysis and with the clinical diagnosis as gold standard for non-criteria aPL.

Results

Assay performance of the LIA for criteria aPL was comparable to that of ALE, ACU, UNI, and AES. For non-criteria aPL, sensitivities of the LIA for aPA-, aPI-, aPS-IgG and aPA-IgM were significantly higher and for aPC-, aPE-, aAnnV-IgG and aPC- and aPE-IgM significantly lower than AES. Specificities did not differ significantly.

Conclusions

The LIA constitutes a valuable diagnostic tool for aPL profiling. It offers increased sensitivity for the detection of aPL against anionic phospholipids. In contrast, ELISAs exhibit strengths for the sensitive detection of aPL against neutral phospholipids.

Postanalytical considerations that may improve the diagnosis or exclusion of haemophilia and von Willebrand disease

von Willebrand disease (VWD) and haemophilia represent the most common inherited or acquired bleeding disorders. However, many laboratories and clinicians may be challenged by their accurate diagnosis or exclusion. Difficulties in diagnosis/exclusion may include analytical issues, where assays occasionally generate an incorrect result (ie representing an analytical error) or have limitations in their measurement range of and/or low analytical sensitivity. Also increasingly recognized is the influence of preanalytical issues on the diagnosis of VWD or haemophilia. Unfortunately, postanalytical considerations are often not well considered in the diagnostic process. Therefore, this narrative review aims to provide an overview of some important postanalytical considerations that may help improve the diagnosis of VWD and haemophilia. This review primarily discusses aspects around reporting of test results. However, we also discuss other less well-recognized postanalytical considerations, including the use of assay ratios to help identify differential diagnoses and then guide further investigation.

Revisiting the Phadia/EliA cut-off values for anticardiolipin and anti-β2-glycoprotein I antibodies: a systematic evaluation according to the guidelines

Background Phadia/EliA fluorescence enzyme immunoassays are widely used automated assays for anticardiolipin (aCL) and anti-β2-glycoprotein I (aβ2GPI) antibodies. To date, cut-off values for these assays have not been evaluated systematically and the evidence behind manufacturer's recommended cut-off values is not clear. Objective To determine Phadia/EliA cut-off values for antiphospholipid antibodies (aPL) according to the procedures suggested by guidelines. Methods A total of 266 blood donors (135 females and 131 males) were included. The pre-handling and analysis of the samples were performed according to the International Society on Thrombosis and Hemostasis (ISTH) guideline for solid phase aPL assays. Cut-off values and corresponding 90% confidence intervals (CI) for each antibody were established and outliers were handled according to the Clinical and Laboratory Standards Institute (CLSI) guideline for reference intervals. Samples from 377 consecutive patients, referred to our thrombophilia center with evidence of thrombosis or pregnancy morbidity were included for aPL testing. Results The in-house 99th (97.5th) percentile cut-off values were 11 (8.7), 12 (6.9) 8.5 (5.0) AU/mL for aβ2GPI IgG, IgM and IgA, and 21 (13) GPL-U/mL and 41 (25) MPL-U/mL for aCL IgG and IgM, respectively. The prevalence of positive results (%) defined by these cut-off values in patients with evidence of thrombosis or pregnancy morbidity was 9.5 (12.2), 1.6 (2.9), and 7.0 (9.9), and 0.8 (3.8) for aβ2GPI IgG, IgM, and aCL IgG and IgM respectively. The use of in-house 99th percentile cut-off values compared to the manufacturer suggested cut-off values resulted in 1 and 39 fewer samples for aβ2GPI and aCL to be classified as positive for aPL, respectively. Conclusions We present Phadia/EliA cut-off values with 90% CI for aPL determined systematically according to the ISTH and CLSI guidelines. These values are different from values previously determined, suggesting variation of aPLs in different populations. Our findings indicate the need for each laboratory to determine/validate assay specific cut-off values for aPL.

Post-analytical Issues in Hemostasis and Thrombosis Testing

Analytical concerns within hemostasis and thrombosis testing are continuously decreasing. This is essentially attributable to modern instrumentation, improvements in test performance and reliability, as well as the application of appropriate internal quality control and external quality assurance measures. Pre-analytical issues are also being dealt with in some newer instrumentation, which are able to detect hemolysis, icteria and lipemia, and, in some cases, other issues related to sample collection such as tube under-filling. Post-analytical issues are generally related to appropriate reporting and interpretation of test results, and these are the focus of the current overview, which provides a brief description of these events, as well as guidance for their prevention or minimization. In particular, we propose several strategies for improved post-analytical reporting of hemostasis assays and advise that this may provide the final opportunity to prevent serious clinical errors in diagnosis.

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.

Lupus anticoagulant mixing tests for multiple reagents are more sensitive if interpreted with a mixing test-specific cut-off than index of circulating anticoagulant

BACKGROUND

Lupus anticoagulant (LA) is classified in the antibody family that is recognized as antiphospholipid antibodies. Guidelines for LA detection recommend mixing test interpretation with either a mixing test specific cut-off (MTC) or index of circulating anticoagulant (ICA). We previously evidenced that MTC was superior to ICA in detecting the in vitro inhibition of LA with a single dilute APTT (activated partial thromboplastin time) and dRVVT (diluted Russell's viper venom time) pairing.

OBJECTIVES

The objective in the present study was to compare the LA diagnostic effectiveness of MTC and ICA by multiple APTT and dRVVT reagents.

METHODS

One hundred-five samples from non-anticoagulated patients positive for LA in the dilute APTT (dAPTT) and dRVVT reagent pairing employed for diagnostic examination were performed by undiluted and in a 1:1 mix with normal pooled plasma with four additional APTT reagents and another dRVVT reagent (dRVVT B).

RESULTS

Frequencies of MTC and ICA positivity were determined from samples LA positive in undiluted plasma. MTC positivity in mixing test were 63%, 77%, 80%, 84%, 46%, 81%, and 72% in 4 APTT, dAPTT and 2 dRVVT, respectively. ICA positivity were 47%, 67%, 58%, 54%, 42%, 47%, and 29%, respectively. There were no samples of ICA-positive/MTC-negative with any reagent.

CONCLUSIONS

The data indicate that MTC is superior to ICA for LA detection in mixing tests in multiple reagents and reagent types. Although mixing tests may make weak LA samples appear negative, the efficacy of LA detection can be improved by the method to interpret the results.

Cell-bound complement activation products in SLE

Diagnosis of SLE is based on clinical manifestations and laboratory findings. Timely diagnosis and treatment are important to control disease activity and prevent organ damage. However, diagnosis is challenging because of the heterogeneity in clinical signs and symptoms, and also because the disease presents with alternating periods of flare and quiescence. As SLE is an autoimmune disease characterised by the formation of autoantibodies, diagnostic immunology laboratory tests for detecting and quantifying autoantibodies are commonly used for the diagnosis and classification of SLE. These include ANA, anti-double-stranded DNA antibodies and anti-Smith antibodies, together with other antibodies such as antiphospholipid or anti-Cq1. Complement proteins C3 and C4 are commonly measured in patients with SLE, but their serum levels do not necessarily reflect complement activation. Cell-bound complement activation products (CB-CAPs) are fragments formed upon complement activation that bind covalently to haematopoietic cells. This review focuses on the complement system and, in particular, on CB-CAPs as biomarkers for the diagnosis and monitoring of SLE, vis-à-vis complement proteins and other biomarkers of complement activation.

Plasma Antiphospholipid Antibodies Effects on Activated Partial Thromboplastin Time Assays

BACKGROUND

Activated partial thromboplastin time (aPTT) assays can be affected by plasma antiphospholipid antibodies (aPLs), but the degree of the interference is not easy to predict. This study aimed to investigate the effects on aPTT assay results of different types and combinations of aPLs, including anti-β₂-glycoprotein I antibodies, anticardiolipin antibodies and lupus anticoagulant.

MATERIALS AND METHODS

We retrospectively collected clinical information and laboratory tests from aPL-positive patients. The potential influence of aPLs on aPTT assays was assessed.

RESULTS

The survey included 589 aPL-positive patients. No significant differences existed in basic characteristics such as sex, age, prothrombin time, fibrinogen and alanine aminotransferase among different cases with 1, 2 or 3 types of positive-aPL markers (P > 0.05). In 113 patients with abnormal aPTT values, multivariable linear regression analysis showed a significant correlation between an abnormal degree of aPTT values and dilute Russell viper venom time (dRVVT) or silica clotting time (SCT) with a correlation coefficient of 0.437 or 0.497 (P < 0.01), whereas age, anticardiolipin antibodies-immunoglobulin G, anticardiolipin antibodies-immunoglobulin M and anti-β₂-glycoprotein I antibodies were of no significance (P > 0.05). Among blood samples with 3 types of aPLs positivity, the rate of abnormal aPTT detection values was 55.3%, which was significantly higher than that observed in patients with negative, single-positive or double-positive aPL markers (P < 0.05). Patients with a moderate to strong dRVVT or SCT had a higher proportion of abnormal aPTT assays than did patients with a low dRVVT or SCT (P < 0.05).

CONCLUSIONS

When abnormal aPTT values are obtained, the influence of aPLs should be considered, especially in the presence of a moderate to strong dRVVT or SCT.

An Overview of Thrombophilia and Associated Laboratory Testing

Venous thromboembolism, usually entailing deep vein thrombosis, pulmonary embolism, or both, is a complex and multifactorial disorder, in which a number of putative conditions interplay and finally contribute to propel the individual risk over a certain degree, so ultimately culminating in the development of venous occlusive disorders. Thrombophilia is commonly defined as a propensity to develop venous thromboembolism on the basis of an underlying hypercoagulable state attributable to inherited or acquired disorders of blood coagulation or fibrinolysis. The thrombophilic conditions are conventionally classified as inherited (or genetically determined) and acquired. The former include deficiencies of natural anticoagulants such as antithrombin, protein C, protein S, increased values of clotting factors (especially factor VIII), as well as prothrombotic polymorphisms in genes encoding for factor V (i.e., factor V Leiden) and prothrombin. The latter conditions mainly entail antiphospholipid antibody syndrome, malignancy, acquired elevations of coagulation factors or acquired reduction of natural inhibitors, or hyperhomocysteinemia. Deepened knowledge of all potential risk factors, as well as the clear understanding of their role in the pathophysiology of venous thrombosis, are both essential to help achieve a faster and more efficient diagnosis of this condition as well as a more effective prophylaxis of patients at higher risk and treatment of those with manifest disease.

Overview of Hemostasis and Thrombosis and Contribution of Laboratory Testing to Diagnosis and Management of Hemostasis and Thrombosis Disorders

Hemostasis is a complex and tightly regulated process whereby the body attempts to maintain a homeostatic balance to permit normal blood flow, without bleeding or thrombosis. When this balance is disrupted, due to trauma or underlying congenital bleeding or thrombotic disorders, clinical intervention may be required. To assist clinicians in diagnosing and managing affected patients, hemostasis laboratories offer an arsenal of tests, both routine (screening) and more specialized (diagnostic). In general, screening assays are used to screen for hemostasis-related disease or to monitor or measure the effect of anticoagulant therapy, which may be applied to treat patients with recent thrombosis or at risk of thrombosis. Diagnostic assays are used to diagnose or exclude specific hemostasis-related diseases, and in some cases, to monitor or measure the effect of anticoagulant therapy, or alternatively procoagulant therapy that may be applied to those at risk of bleeding. This chapter provides an overview of hemostasis and thrombosis with respect to laboratory tests that may be applied to affected patients.

Current Controversies in Lupus Anticoagulant Detection

Antiphospholipid syndrome is an autoimmune, acquired thrombophilia diagnosed when vascular thrombosis or pregnancy morbidity are accompanied by persistent antiphospholipid antibodies. Lupus anticoagulants (LA) are one of the criteria antibodies but calibration plasmas are unavailable and they are detected by inference based on antibody behaviour in a medley of coagulation-based assays. Elevated screening tests suggest the presence of a LA, which is confirmed with mixing tests to evidence inhibition and confirmatory tests to demonstrate phospholipid-dependence. At least two screening tests of different principle must be used to account for antibody heterogeneity and controversy exists on whether assays, in addition to dilute Russell's viper venom time and activated partial thromboplastin time, should be employed. A variety of approaches to raw data manipulation and interpretation attract debate, as does inclusion or exclusion of mixing studies in circumstances where the presence of a LA is already evident from other results. Therapeutic anticoagulation compromises coagulation-based assays but careful data interpretation and use of alternative reagents can detect or exclude LA in specific circumstances, and this aspect of LA detection continues to evolve. This review focuses on the main areas of debate in LA detection.

The Significance of Anti-Beta-2-Glycoprotein I Antibodies in Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is a thrombophilic disorder that classically presents with vascular thrombosis and/or obstetric complications. APS is associated with antiphospholipid antibodies: a heterogeneous group of autoantibodies that are directed against membrane phospholipids in complex with phospholipid-binding proteins. Beta-2-glycoprotein I (B2GPI) binds anionic phospholipids and is considered to be the predominant antigen in APS and antibodies against B2GPI (anti-B2GPI) are recognised in the laboratory criteria for APS diagnosis. This review focuses on the part played by anti-B2GPI in the pathogenesis of APS, their associations with different clinical phenotypes of the disorder and new avenues for refining the diagnostic potential of anti-B2GPI testing.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Analytical and clinical comparison of different immunoassay systems for the detection of antiphospholipid antibodies

INTRODUCTION

We evaluated analytical and clinical performances of IgG and IgM anticardiolipin (aCL) antibodies and anti-β2-glycoprotein I (a-β2GpI) antibodies and upper limit reference ranges (99th percentiles) in comparison with manufacturer's cutoff values with different commercial methods.

METHODS

We assayed aCL and a-β2GpI in serum samples from 30 healthy individuals, 77 patients with antiphospholipid syndrome (APS) diagnosed according to the Sydney criteria, 51 patients with autoimmune diseases, eight patients with previous thrombotic events, six patients with other diseases, and 18 patients with infectious diseases, using ELISA Inova Diagnostics; EliA Phadia Laboratory Systems; CliA Zenit-RA; and CliA Bio-Flash.

RESULTS

Anticardiolipin and a-β2GpI IgG and IgM immunoassays showed good analytic performances with both 99th percentile and manufacturer's cutoff reference values. Our results showed fair to moderate agreement among assays. In-house cutoff values gave significantly better performances only for a-β2GpI IgG with all the immunoassays analyzed with the exception of Inova CliA Bio-Flash where we obtained the same performances with in-house and manufacturer's cutoffs.

CONCLUSIONS

By guidelines, all laboratories are strongly advised to validate/verify the manufacturer's cutoff values. We recommend establishing low-positive, medium-/high-positive, and high-positive CliA IgG aCL and a-β2GpI ranges in order to help clinicians in the diagnosis and treatment of APS.

Altered Traffic of Cardiolipin during Apoptosis: Exposure on the Cell Surface as a Trigger for "Antiphospholipid Antibodies"

Apoptosis has been reported to induce changes in the remodelling of membrane lipids; after death receptor engagement, specific changes of lipid composition occur not only at the plasma membrane, but also in intracellular membranes. This paper focuses on one important aspect of apoptotic changes in cellular lipids, namely, the redistribution of the mitochondria-specific phospholipid, cardiolipin (CL). CL predominantly resides in the inner mitochondrial membrane, even if the rapid remodelling of its acyl chains and the subsequent degradation occur in other membrane organelles. After death receptor stimulation, CL appears to concentrate into mitochondrial “raft-like” microdomains at contact sites between inner and outer mitochondrial membranes, leading to local oligomerization of proapoptotic proteins, including Bid. Clustering of Bid in CL-enriched contacts sites is interconnected with pathways of CL remodelling that intersect membrane traffic routes dependent upon actin. In addition, CL association with cytoskeleton protein vimentin was observed. Such novel association also indicated that CL molecules may be expressed at the cell surface following apoptotic stimuli. This observation adds a novel implication of biomedical relevance. The association of CL with vimentin at the cell surface may represent a “new” target antigen in the context of the apoptotic origin of anti-vimentin/CL autoantibodies in Antiphospholipid Syndrome.

"New" antigenic targets and methodological approaches for refining laboratory diagnosis of antiphospholipid syndrome

Antiphospholipid antibodies (aPLs) are a heterogeneous group of antibodies directed against phospholipids or protein/phospholipid complexes. Currently, aPLs are assessed using either "solid-phase" assays that identify anticardiolipin antibodies and anti-β2-glycoprotein I antibodies or "liquid-phase" assay that identifies lupus anticoagulant. However, in the last few years, "new" antigenic targets and methodological approaches have been employed for refining laboratory diagnosis of antiphospholipid syndrome (APS). In this review the potential diagnostic value of antibodies to domains of β2-GPI, prothrombin/phosphatidylserine, vimentin/cardiolipin, protein S, protein C, annexin A2, annexin A5, and phospholipid antigens is discussed. Moreover, new technical approaches, including chemiluminescence, multiline dot assay, and thin layer chromatography (TLC) immunostaining, which utilize different supports for detection of aPL, have been developed. A special focus has been dedicated on "seronegative" APS, that is, those patients with a clinical profile suggestive of APS (thromboses, recurrent miscarriages, or foetal loss), who are persistently negative for the routinely used aPL. Recent findings suggest that, in sera from patients with SN-APS, antibodies may be detected using "new" antigenic targets (mainly vimentin/cardiolipin) or methodological approaches different from traditional techniques (TLC immunostaining). Thus, APS represents a mosaic, in which antibodies against different antigenic targets may be detected thanks to the continuously evolving new technologies.

Reflections on the next generation of hemostasis instrumentation. A glimpse into the future?

Hemostasis testing is conventionally referred to as performance of in vitro diagnostic tests for screening, diagnosis and therapeutic management of patients with either bleeding or thrombotic disorders. The ongoing revolution of diagnostic testing, squeezed between reduced funding and increasing volumes, carries notable implications in the way laboratory resources are organized and coagulation tests delivered. It is therefore predictable that the newer generation of hemostasis analyzers may be designed to face these emerging needs whilst maintaining a high degree in the quality of testing. In this opinion paper, we aim to discuss some concepts of redesigning coagulation analyzers in consideration of the most important aspects of the preanalytical, analytical and postanalytical phases in hemostasis testing.