Lupus Anticoagulant Testing: Diluted Russell Viper Venom Time (dRVVT)

Risk Factors of Thrombophilia-Related Mutations for Early and Late Pregnancy Loss

Background and Objectives: This retrospective cohort study investigates the role of genetic thrombophilia in pregnant women experiencing early pregnancy loss compared to those with late pregnancy loss. Materials and Methods: Participants were categorized into early and late pregnancy loss groups based on gestational age. A total of 156 patients were included, out of which 103 had early-trimester pregnancy losses and 96 had multiple miscarriages. Results: The study revealed a synergistic effect of Factor V Leiden (FVL G1691A) and Methylenetetrahydrofolate Reductase (MTHFR C677T) mutations (coefficient 3.42). Prothrombin (PT) G20210A and β-Fibrinogen 455 G>A mutations exhibited a significant interaction (coefficient 1.98). Additionally, MTHFR A1298C and Plasminogen Activator Inhibitor-1 (PAI-1 4G/5G) mutations showed a significant interaction (coefficient 1.65). FVL G1691A and Endothelial Protein C Receptor (EPCR) allele A1/A2 mutations also demonstrated a significant association (coefficient 2.10). Lastly, MTHFR C677T and Glycoprotein IIb/IIIa T1565C mutations interacted significantly (coefficient 1.77). Risk factor analysis identified several mutations associated with early pregnancy loss, including PAI-1 4G/5G homozygous (OR 3.01), FVL G1691A heterozygous (OR 1.85), and MTHFR A1298C heterozygous (OR 1.55). Both homozygous and heterozygous MTHFR C677T mutations were significant risk factors (OR 2.38; OR 2.06), as was PT G20210A homozygous mutation (OR 1.92). The PAI-1 4G/4G homozygous variant posed a risk (OR 1.36). Late pregnancy loss was associated with MTHFR A1298C homozygous mutation (OR 3.79), β-Fibrinogen 455 G>A heterozygous mutation (OR 2.20), and MTHFR A1298C heterozygous mutation (OR 2.65). Factor XIII G1002T heterozygous mutation (OR 1.18) and PAI-1 4G/5G homozygous mutation (OR 2.85) were also significant risk factors. EPCR allele A1/A2 (OR 1.60) and A2/A3 (OR 1.73) mutations were identified as significant risk factors for late pregnancy loss. Furthermore, FVL G1691A homozygous mutation, PT G20210A homozygous mutation, MTHFR C677T heterozygous mutation, MTHFR A1298C heterozygous mutation, and EPCR allele A1/A2 were identified as significant risk factors for multiple miscarriage. Conclusions: This study highlights significant interactions and risk factors related to genetic thrombophilia mutations in different types of pregnancy loss, contributing valuable insights for miscarriage management guidelines.

Testing for the lupus anticoagulant: the good, the bad, and the ugly

Lupus anticoagulant (LA) represents 1 of the laboratory criteria for classification of patients as having definite antiphospholipid syndrome (APS). The other 2 laboratory criteria are anticardiolipin antibodies and anti-beta2-glycoprotein I antibodies. At least 1 of these antiphospholipid antibody (aPL) tests need to be positive, with evidence of persistence, together with evidence of at least 1 clinical criterion for APS, before a patient can be classified as having definite APS. LA and other aPL assays are also important for diagnosis or exclusion of APS, as well as for risk stratification, with triple-positive patients carrying the greatest risk. Whereas LA is identified through "uncalibrated" clot-based assays, the other aPL assays (anticardiolipin and anti-beta2-glycoprotein I antibodies) represent immunological assays, identified using calibrated solid-phase methods. Because LA is identified using clot-based assays, it is subject to considerable preanalytical and analytical issues that challenge accurate detection or exclusion of LA. In this narrative review, we take a look at the good, the bad, and the ugly of LA testing, primarily focusing on the last 10 years. Although harmonization of LA testing as a result of International Society on Thrombosis and Haemostasis guidance documents and other international activities has led to improvements in LA detection, many challenges remain. In particular, several anticoagulants, especially direct oral anticoagulants and also vitamin K antagonists, given as therapy to treat the pathophysiological consequences of aPL, especially thrombosis, interfere with LA assays and can generate false-positive or false-negative LA findings. Overcoming these diagnostic errors will require a multifaceted approach with clinicians and laboratories working together.

Determining Thrombogenicity: Using a Modified Thrombin Generation Assay to Detect the Level of Thrombotic Event Risk in Lupus Anticoagulant-Positive Patients

The aim of this study was to determine the thrombogenicity of lupus anticoagulant (LA) antibodies using a modified thrombin generation assay (TGA) with the addition of activated protein C (APC) in a group of 85 patients with LA-positive samples. Of these, 58 patients had clinical manifestations of antiphospholipid syndrome (APS) according to the Sydney criteria classification, i.e., each patient had thrombosis or foetal loss, and 27 patients did not show any clinical manifestations of APS. A comparison of the two groups' TGA results revealed statistically significant differences (Fisher's test p = 0.0016). The group of patients exhibiting clinical manifestations of APS showed higher thrombogenicity in 56.9% of patients, while the group of patients not yet exhibiting clinical manifestations of APS showed higher thrombogenicity in 25.9% of patients. There were no significant differences in the specificity of the TGA test between the groups of patients exhibiting similar clinical manifestations. Receiver operating characteristic curve analysis showed a more significant relationship (p = 0.0060) for TGA than for LA titre (p = 0.3387). These data suggest that the determination of LA thrombogenicity with the TGA assay leads to an increased prediction of the manifestation of a thromboembolic event. Our findings appear to be particularly relevant for the prediction of thrombotic events in patients with laboratory-expressed APS and no clinical manifestations.

A Successful Pregnancy Outcome After Continued Surveillance of Lupus Anticoagulant Antibodies in a Patient With Recurrent Pregnancy Loss: A Case Report and Literature Review

Recurrent pregnancy loss (RPL) can be a devastating experience for individuals trying to have children. Various potential causes contribute to the multifactorial pathogenesis of RPL, including chromosomal anomalies, endocrine conditions, autoimmunity, thrombophilias, and infectious agents. Antinuclear antibodies (ANAs) offer an unspecific clue to the underlying autoimmune pathogenic etiology of RPL. This case details a 40-year-old female with a history of RPL, fibromyalgia, and ANA positivity, who spontaneously developed lupus anticoagulant antibodies during her second trimester of pregnancy. Although the recommended American Society of Reproductive Medicine (ASRM) diagnostic criteria for initiating a thrombophilia evaluation was not formally met, the patient's maintenance of low-molecular-weight heparin (LMWH) throughout her pregnancy may have contributed to the success of the pregnancy. When treating a patient with RPL, consideration of the comprehensive clinical picture should precede the need to strictly adhere to published criteria for using non-proven clinical interventions. A risk-benefit analysis ought to be considered when offering patients additional medications that may come with some risks but could significantly improve the chances of a successful clinical outcome, such as live birth. We aim to provide evidence to promote greater flexibility in guidelines so that a patient's unique autoimmune etiologies of RPL are not overlooked.

An Acute Need Inspiration: Autoneutralization of Lupus Anticoagulants in Affected Prothrombin Times (PT) and Activated Partial Thromboplastin Times (APTT)

Lupus anticoagulants are antibodies directed to phospholipids (PL) and in particular represent an in vitro phenomenon where these antibodies bind to PL in coagulation reagents creating an artificial prolongation of the activated partial thromboplastin time (APTT) and sometimes also prothrombin time (PT) clotting times. Prolongation of LA-induced clotting times is typically not associated with bleeding risk. However, the degree of prolongation may cause some trepidation for clinicians that will be performing delicate surgeries or those with high bleeding risks, so a mechanism to alleviate their anxiety may be prudent. As such, an autoneutralizing method to mitigate or eliminate the LA effect on the PT and APTT may be beneficial. In this document, the detailing of an autoneutralizing procedure to diminish the LA effect on the PT and APTT will be provided.

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.

Single or triple positivity for antiphospholipid antibodies in "carriers" or symptomatic patients: Untangling the knot

BACKGROUND

Although the triple positivity of antiphospholipid antibodies (aPL) is important for classifying high-risk patients, interpretation of aPL positivity, namely the lupus anticoagulant (LA), anti-cardiolipin (aCL), and anti-beta2-glycoprotein I autoantibodies (aB2GPI) remains challenging for thrombotic risk stratification.

OBJECTIVE

To compare biological and clinical data between triple aPL- and single aCL-positive patients.

METHODS

Of the 6500 patients assayed for aPL in daily practice within 3 years, we retrospectively analyzed data from 161 patients that were either triple aPL-positive or single aCL-positive with 5 years' follow-up for 121 of them.

RESULTS

Whatever triple or single aPL positivity, we found a high prevalence of "carrier" patients (43%), which led us to question the clinical relevance of the triple aPL positivity. This result also justified the need to identify high-risk profiles. In asymptomatic patients, high risk of thrombotic events is associated with (1) two positive tests for LA or a Rosner Index >27 combined with both aCL-IgG and aB2GPI-IgG positivity, (2) persistent single aCL positivity without an associated autoimmune disease. In symptomatic patients, we demonstrated differences in the phenotype of patients and their therapeutic anticoagulation according to the number of positive aPL but we did not find differences in the number of clinical events, recurrence, or relapse, even in the absence of treatment.

CONCLUSION

This study shows that the thrombotic risk does not necessarily increase with the number of positive tests and raises the question of the therapeutic management of single aCL-positive patients.

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.

Inhibitor Index in the Clot Waveform Analysis-Based Mixing Test Differentiates among Hemophilia A without and with Inhibitors, and Lupus Anticoagulant

BACKGROUND

 The mixing test is used to identify the pathway to follow-up testing and is also useful for the investigation of lupus anticoagulant (LA) positivity. "To completely correct" indicates clotting factor deficiency, while "to not correct" indicates the presence of a clotting factor inhibitor including LA. "Index of circulation anticoagulant" and/or "percent correction" is used to interpret the results of mixing studies, but it does not accurately differentiate factor inhibitors from LA.

AIM

 To precisely differentiate hemophilia A (HA), HA with inhibitor (HA-inh), and LA using the clot waveform analysis (CWA)-based mixing test.

METHODS

 Plasma samples from HA, LA, and HA-inh including acquired HA were incubated with normal plasma in 9:1, 1:1, and 1:9 mix ratios. From activated partial thromboplastin time CWA at 0-minute (immediately) and 12-minute incubation, the ratios of CWA parameters at 12 minutes/0 minute (inhibitor index) were assessed.

RESULTS

 The inhibitor index values of CWA parameters obtained using the mixing test in a 1:1 ratio demonstrated a significant difference between HA-inh and LA but could not differentiate LA from HA-inh completely. Plasmas used for the mixing tests in 9:1 and 1:9 ratios were able to fully distinguish between HA-inh (>0.5 BU/mL) and LA. These indices significantly correlated with inhibitor titer below 40 BU/mL (r > 0.90), possibly estimating FVIII inhibitor titer from the inhibitor index. Plasmas in HA and LA could be distinguished by mixing in a 1:1 ratio at 0 minute (immediately).

CONCLUSION

 The inhibitor index from CWA-based mixing tests with a 12-minute incubation could differentiate among HA, HA-inh, and LA quickly.

The Procoagulant Snake Venom Serine Protease Potentially Having a Dual, Blood Coagulation Factor V and X-Activating Activity

A procoagulant snake venom serine protease was isolated from the venom of the nose-horned viper (Vipera ammodytes ammodytes). This 34 kDa glycoprotein, termed VaaSP-VX, possesses five kDa N-linked carbohydrates. Amino acid sequencing showed VaaSP-VX to be a chymotrypsin-like serine protease. Structurally, it is highly homologous to VaaSP-6 from the same venom and to nikobin from the venom of Vipera nikolskii, neither of which have known functions. VaaSP-VX does not affect platelets. The specific proteolysis of blood coagulation factors X and V by VaaSP-VX suggests that its blood-coagulation-inducing effect is due to its ability to activate these two blood coagulation factors, which following activation, combine to form the prothrombinase complex. VaaSP-VX may thus represent the first example of a serine protease with such a dual activity, which makes it a highly suitable candidate to replace diluted Russell’s viper venom in lupus anticoagulant testing, thus achieving greater reliability of the analysis. As a blood-coagulation-promoting substance that is resistant to serpin inhibition, VaaSP-VX is also interesting from the therapeutic point of view for treating patients suffering from hemophilia.

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.

Evaluation of the DOAC-Stop® Procedure to Overcome the Effect of DOACs on Several Thrombophilia Screening Tests

The impact of direct oral anticoagulants (DOACs) on laboratory assays used for thrombophilia testing (e.g., antithrombin, protein S, protein C, lupus anticoagulant and activated protein-C resistance) is a well-known issue and may cause false-positive and -negative results. Therefore, the correct interpretation of tests that are performed in patients taking DOACs is mandatory to prevent misclassification and the subsequent clinical consequences. We aimed at evaluating the efficiency of a new and simple procedure (DOAC-Stop®; Haematex Research, Hornsby, Australia) to overcome the effect of all DOACs in real-life settings and to assess the percentage of erroneous results due to the presence of DOACs on thrombophilia screening tests. For this purpose, 135 DOAC-treated patients (38 apixaban, 40 dabigatran, 15 edoxaban, and 42 rivaroxaban) and 20 control patients were enrolled. A significant drop in apixaban, dabigatran, edoxaban, and rivaroxaban plasma concentrations following the DOAC-Stop® treatment was observed (74.8–8.2 ng/mL [ p  < 0.0001], 95.9–4.7 ng/mL [ p  < 0.0001], 102.1–8.8 ng/mL [ p  = 0.001], and 111.3–7.0 ng/mL [ p  < 0.0001], respectively). The DOAC-Stop® treatment was mostly effective to overcome the effect of DOACs on PTT-LA, dilute Russell's viper venom time (dRVVT) screen, and dRVVT confirm tests. Using our procedures, false-positive results due to DOACs were observed only with lupus anticoagulant tests (up to 75%) and fell to zero after the DOAC-Stop® procedure, regardless of the DOAC considered. In conclusion, the DOAC-Stop® adsorbent procedure appeared to be an effective and simple way to overcome the interference of DOAC on coagulation tests and should facilitate the interpretation of thrombophilia screening tests in patients taking DOACs.