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

Taipan snake venom time has high sensitivity for lupus anticoagulants in non-anticoagulated, triple positive antiphospholipid syndrome patients

INTRODUCTION

Dilute Russell's viper venom time (dRVVT) and activated partial thromboplastin time (APTT) are the mainstay assays in lupus anticoagulant (LA) detection yet they have limitations, particularly in relation to interferences and specificity. The recently validated Taipan snake venom time (TSVT) screening with ecarin time (ET) confirmatory assays overcome many of those limitations due to the innate specificity engendered from direct prothrombin activation, and insensitivity to the effects of vitamin K antagonists (VKA). The present study aimed to further evidence diagnostic utility of TSVT/ET by performing them in samples from 116 nonanticoagulated patients with established triple-positive antiphospholipid syndrome (APS).

METHODS

Samples were identified in three expert centres who performed dRVVT, APTT and solid phase antiphospholipid antibody assays with reagents from a variety of manufacturers. All samples additionally received TSVT/ET analysis using standardised reagents.

RESULTS

Ninety seven of 116 (83.6%) were dRVVT- and APTT-positive, 85/97 (87.6%) of which were TSVT/ET-positive, 9/116 (7.8%) were dRVVT-positive only, 6 of which were TSVT/ET-positive, and 10/116 (8.6%) were APTT-positive only, 5 of which were TSVT/ET-positive. 96/116 TSVT/ET-positivity returned a high sensitivity for LA of 82.8%. Low coefficients of determination revealed weak relationships between LA potency and anticardiolipin and anti-β2-glycoprotein I antibody titres for all three LA assays.

CONCLUSIONS

TSVT/ET has high sensitivity for the clinically significant LA found in triple positive APS patients. TSVT/ET can establish multiple LA assay positivity in nonanticoagulated patients negative for one of dRVVT or APTT, and is the only assay pairing insensitive to VKAs, the recommended anticoagulation for APS.

Lipid-binding antiphospholipid antibodies: significance for pathophysiology and diagnosis of the antiphospholipid syndrome

The antiphospholipid syndrome (APS) is an autoimmune disease characterized by the presence of pathogenic antiphospholipid antibodies (aPL). Since approximately 30 years ago, lipid-binding aPL, which do not require a protein cofactor, have been regarded as irrelevant for APS pathogenesis even though anticardiolipin are a diagnostic criterion of APS. In this review, we will summarize the available evidence from in vitro studies, animal models, and epidemiologic studies, which suggest that this concept is no longer tenable. Accordingly, we will only briefly touch on the role of other aPL in APS. This topic has been amply reviewed in detail elsewhere. We will discuss the consequences for laboratory diagnostics and future research required to resolve open questions related to the pathogenic role of different aPL specificities.

Risk Factors for Antiphospholipid Antibodies and Antiphospholipid Syndrome

Persistence of serum antiphospholipid antibodies (aPL) is associated with a high thrombotic risk, both arterial and venous, and with pregnancy complications. Due to the potential morbidity and mortality associated with the presence of aPL, identifying and recognizing risk factors for the development of aPL and thrombosis in aPL carriers may help to prevent and reduce the burden of disease. Multiple elements are involved in the pathomechanism of aPL development and aPL-related thrombosis such as genetics, malignancy, and infections. This review will address the role of both well-known risk factors and their evolution, and of emerging risk factors, including COVID-19, in the development of aPL and thrombosis in aPL carriers.

Triple-positive antiphospholipid syndrome does not guarantee positivity in each lupus anticoagulant assay

BACKGROUND

Triple positivity for all 3 criteria antiphospholipid antibodies confers high risk of symptom development in carriers, and recurrence in antiphospholipid syndrome (APS). Most triple-positivity studies report lupus anticoagulant (LA) testing as positive without distinguishing between positivity with dilute Russell's viper venom time (dRVVT) and activated partial thromboplastin time (APTT) and single-assay positivity or only perform dRVVT. Single LA assay repertoires remain in use in some centers, which risks missing some triple positives. Positivity with both assays may identify higher risk.

OBJECTIVES

The aim of this study is to investigate the frequency of single LA assay positivity in triple-positive patients.

METHODS

Three hundred forty-two triple-positive profiles from nonanticoagulated patients (237 APS, 45 systemic lupus erythematosus without APS symptoms, and 60 nonclinical criteria) were identified from laboratory databases and assessed for LA positivity by dRVVT and/or APTT.

RESULTS

Seventy-three of 237 (30.8%) APS samples were LA-positive with 1 assay, 40/237 (16.9%) by dRVVT only, and 33/237 (13.9%) with APTT only. Nineteen of 45 (42.2%) were LA-positive with 1 assay in the systemic lupus erythematosus cohort; 12/45 (26.7%) with dRVVT only and 7/45 (15.5%) with APTT only. Thirty-three of 60 (55.0%) were LA-positive with 1 assay in the nonclinical criteria cohort; 24/60 (40.0%) with dRVVT only and 9/60 (15.0%) with APTT only. The most common solid-phase assay profile was elevated immunoglobulin G aCL and aβ2GPI.

CONCLUSION

Up to 55.0% of triple-positive samples were positive in 1 LA assay, representing significant potential for misdiagnosis and inappropriate management via single LA assay repertoires.

Survey on antiphospholipid syndrome diagnosis and antithrombotic treatment in patients with ischemic stroke, other brain ischemic injury, or arterial thromboembolism in other sites: communication from ISTH SSC Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibodies

BACKGROUND

The optimal strategy for diagnosis and antithrombotic treatment of patients with antiphospholipid syndrome (APS)-associated acute ischemic stroke (AIS), transient ischemic attack (TIA), or other brain ischemic injury is poorly defined.

OBJECTIVES

The survey goal was to capture variations in diagnosis and antithrombotic treatment of APS-associated ischemic stroke and related disorders to inform guidance and clinical trials to define optimal management.

METHODS

Professional colleagues, including key opinion leaders, were invited to complete a REDCap survey questionnaire initiated by the International Society on Thrombosis and Haemostasis Scientific and Standardisation Committee Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibodies. The survey data were tallied using simple descriptive statistics.

RESULTS

There was generally good agreement on several aspects, including which patients to test for antiphospholipid antibodies (aPL), use of a lifelong vitamin K antagonist for AIS or recurrent TIA, and formal cognitive assessment for suspected cognitive impairment. There was less agreement on other aspects, including aPL testing for brain ischemic injury other than AIS/TIA or if an alternative cause for AIS or TIA exists; choice of aPL tests, their timing, and age cutoff; the aPL phenotype to trigger antithrombotic treatment; management for patent foramen ovale; antithrombotic treatment for first TIA or white matter hyperintensities; head magnetic resonance imaging specifications; and low-molecular-weight heparin dosing/anti-Xa monitoring in pregnancy. The survey highlighted that approximately 25% practice at dedicated APS clinics and <50% have a multidisciplinary team structure for patients with APS.

CONCLUSION

Much of the variation in practice reflects the lack of evidence-based recommendations. The survey results should inform the development of a more uniform multidisciplinary consensus approach to diagnosis and antithrombotic treatment.

Persistence of antiphospholipid antibodies over time and its association with recurrence of clinical manifestations: A longitudinal study from a single centre

PURPOSE

To analyze the antiphospholipid antibody (aPL) persistence over time in patients with antiphospholipid syndrome (APS) and its association with clinical recurrence and to identify predictors of aPL persistence over time.

PATIENTS AND METHODS

200 patients with a diagnosis of APS and at least three follow-up aPL determinations were included. Persistent aPL profile was defined as the presence of lupus anticoagulant (LAC) and/or IgG/IgM anticardiolipin (aCL) and/or IgG/IgM anti-β2 glycoprotein-I (aβ2GPI) (> 99th percentile) antibodies in at least 66% of follow-up measurements. Multilevel mixed-effect generalized linear models with logit link were used.

RESULTS

112 (56%) patients maintained persistent aPL profiles over time, while 88 (44%) were transient. Median follow-up time was 172.5 months. Follow-up time did not affect the odds of aPL persistence in multivariate analysis (p = 1.00). Baseline triple aPL positivity [OR 78 (95%CI 16.9-359.7, p < 0.001)] and double aPL positivity [OR = 7.6 (95%CI 3.7-15.7, p < 0.001)] correlated with persistent aPLs over time, while isolated LAC [OR = 0.26 (95% CI 0.08-0.49, p = 0.002)] or isolated IgG/IgM aCL [OR = 0.20 (95% CI 0.11-0.59, p = 0.004)] positivity, were predictors of transient aPL profile. Patients with persistent aPLs had higher rate of clinical recurrence in comparison to patients with transient aPLs [OR = 2.48 (95%CI 1.34-4.58, p = 0.003)].

CONCLUSIONS

More than half of patients with baseline medium-high titer aPL positivity had persistent positive aPLs over time. Patients with persistent aPLs were more prone to present recurrence of clinical manifestations. Multiple aPL positivity increased the odds of a persistent aPL profile over time, while isolated LAC and aCL positivity decreased it.

Association between interferon-I producing plasmacytoid dendritic cells and thrombotic antiphospholipid syndrome

Background: Thrombotic risk in antiphospholipid syndrome (APS) is conferred by the association of antiphospholipid (aPL) antibodies (first hit) with additional pro-coagulant stimulus (second hit), such as inflammation. Among inflammatory responses, the production of large amounts of interferon (IFN)-I by plasmacytoid dendritic cells (pDCs) is at the basis of the pathophysiology of systemic autoimmune disorders, which raises the hypothesis that this mechanism could also be associated with vascular manifestations of APS. Purpose: Here, we determined the association of pDCs and IFN-I production with thrombotic APS. Research design: Patients with thrombotic primary (t-PAPS) and secondary APS (t-SAPS), asymptomatic aPL carriers and individuals without thrombosis (controls) were included. Data collection and analysis: Circulating pDCs and IFN-α intracellular expression (in the presence or not of oligodeoxynucleotides (CP) stimulus) were quantified by flow cytometry. The expression of five IFN-I inducing genes: ISG15, OASL, Ly6E, MX1, and OAS1 in mononuclear cells was determined by qPCR. Between-group differences were evaluated using chi-square or Kruskal-Wallis tests. Results: A total of 50 patients with t-PAPS, 50 patients with t-SAPS, 20 aPL carriers, and 50 individuals without thrombosis (controls) were included. Intracellular expression of IFN-α was increased after CPG stimulation in both t-SAPS (1.56%; IQR 1.07-2.02) and t-PAPS (0.96%; IQR 0.55-1.24), when compared to aPL carriers (0.71%; IQR 0.42-0.93) and controls (0.48%; IQR 0.24-0.78; p < .0001). ISG15, OASL, Ly6E, MX1, and OAS1 mRNA expressions were higher in t-SAPS (but not in t-PAPS) than in aPL carriers and controls. The expression of proteins and mRNA related to IFN-I response was similar between the triple aPL-positive profile and other aPL profiles. Conclusion: Our results indicate an association of IFN-I response and t-APS. Since IFN-I expression was not increased in aPL carriers or associated with a higher-risk aPL profile, this mechanism does not appear to be related to the presence of aPL alone. IFN-I response could possibly constitute a complementary mechanism for triggering clinical manifestations in APS.

Laboratory Diagnosis of Antiphospholipid Syndrome: Insights and Hindrances

Diagnosis of antiphospholipid syndrome (APS) requires the presence of a clinical criterion (thrombosis and/or pregnancy morbidity), combined with persistently circulating antiphospholipid antibodies (aPL). Currently, laboratory criteria aPL consist of lupus anticoagulant (LAC), anticardiolipin antibodies (aCL) IgG/IgM, and anti-β2 glycoprotein I antibodies (aβ2GPI) IgG/IgM. Diagnosis and risk stratification of APS are complex and efforts to standardize and optimize laboratory tests have been ongoing since the initial description of the syndrome. LAC detection is based on functional coagulation assays, while aCL and aβ2GPI are measured with immunological solid-phase assays. LAC assays are especially prone to interference by anticoagulation therapy, but strategies to circumvent this interference are promising. Alternative techniques such as thrombin generation for LAC detection and to estimate LAC pathogenicity have been suggested, but are not applicable yet in routine setting. For aCL and aβ2GPI, a lot of different assays and detection techniques such as enzyme-linked immunosorbent and chemiluminescent assays are available. Furthermore, a lack of universal calibrators or standards results in high variability between the different solid-phase assays. Other non-criteria aPL such as anti-domain I β2 glycoprotein I and antiphosphatidylserine/prothrombin antibodies have been suggested for risk stratification purposes in APS, while their added value to diagnostic criteria seems limited. In this review, we will describe laboratory assays for diagnostic and risk evaluation in APS, integrating applicable guidelines and classification criteria. Current insights and hindrances are addressed with respect to both laboratory and clinical implications.