Monitoring of anticoagulation in thrombotic antiphospholipid syndrome

Rivaroxaban for stroke patients with antiphospholipid syndrome (RISAPS): protocol for a randomized controlled, phase IIb proof-of-principle trial

Background

Optimal secondary prevention antithrombotic therapy for patients with antiphospholipid syndrome (APS)-associated ischemic stroke, transient ischemic attack, or other ischemic brain injury is undefined. The standard of care, warfarin or other vitamin K antagonists at standard or high intensity (international normalized ratio (INR) target range 2.0-3.0/3.0-4.0, respectively), has well-recognized limitations. Direct oral anticoagulants have several advantages over warfarin, and the potential role of high-dose direct oral anticoagulants vs high-intensity warfarin in this setting merits investigation.

Objectives

The Rivaroxaban for Stroke patients with APS trial (RISAPS) seeks to determine whether high-dose rivaroxaban could represent a safe and effective alternative to high-intensity warfarin in adult patients with APS and previous ischemic stroke, transient ischemic attack, or other ischemic brain manifestations.

Methods

This phase IIb prospective, randomized, controlled, noninferiority, open-label, proof-of-principle trial compares rivaroxaban 15 mg twice daily vs warfarin, target INR range 3.0-4.0. The sample size target is 40 participants. Triple antiphospholipid antibody-positive patients are excluded. The primary efficacy outcome is the rate of change in brain white matter hyperintensity volume on magnetic resonance imaging, a surrogate marker of presumed ischemic damage, between baseline and 24 months follow-up. Secondary outcomes include additional neuroradiological and clinical measures of efficacy and safety. Exploratory outcomes include high-dose rivaroxaban pharmacokinetic modeling.

Conclusion

Should RISAPS demonstrate noninferior efficacy and safety of high-dose rivaroxaban in this APS subgroup, it could justify larger prospective randomized controlled trials.

Clinical guidance for unfractionated heparin dosing and monitoring in critically ill patients

INTRODUCTION

Unfractionated heparin is a widely used anticoagulant in critically ill patients. It has a well-established safety profile and remains an attractive option for clinicians due to its short half-life and reversibility. Heparin has a unique pharmacokinetic profile, which contributes to significant inter-patient and intra-patient variability in effect. The variability in anticoagulant effect combined with heparin's short half-life mean close monitoring is required for clinical efficacy and preventing adverse effects. To optimize heparin use in critically ill patients, effective monitoring assays and dose adjustment strategies are needed.

AREAS COVERED

This paper explores the use of heparin as an anticoagulant and optimal approaches to monitoring in critically ill patients.

EXPERT OPINION

Conventional monitoring assays for heparin dosing have significant limitations. Emerging data appear to favor using anti-Xa assay monitoring for heparin anticoagulation, which many centers have successfully adopted as the standard. The anti-Xa assay appears have important benefits relative to the aPTT for heparin monitoring in critically ill patients, and should be considered for broader use.

Unlocking the potential of fondaparinux: guideline for optimal usage and clinical suggestions (2023)

Background: Thromboembolic disease is associated with a high rate of disability or death and gravely jeopardizes people's health and places considerable financial pressure on society. The primary treatment for thromboembolic illness is anticoagulant medication. Fondaparinux, a parenteral anticoagulant medicine, is still used but is confusing due to its disparate domestic and international indications and lack of knowledge about its usage. Its off-label drug usage in therapeutic settings and irrational drug use are also common. Objective: The aim of this guideline is to enhance the judicious clinical application of fondaparinux by consolidating the findings of evidence-based research on the drug and offering superior clinical suggestions. Methods: Seventeen clinical questions were developed by 37 clinical pharmacy experts, and recommendations were formulated under the supervision of three methodologists. Through methodical literature searches and the use of recommendation, assessment, development and evaluation grading techniques, we gathered evidence. Results: This guideline culminated in 17 recommendations, including the use of fondaparinux for venous thromboembolism (VTE) prevention and treatment, perioperative surgical prophylaxis, specific diseases, special populations, bleeding and overdose management. For different types of VTE, we recommend first assessing thrombotic risk in hospitalized patients and then administering the drug according to the patient's body mass. In surgical patients in the perioperative period, fondaparinux may be used for VTE prophylaxis, but postoperative use usually requires confirmation that adequate hemostasis has been achieved. Fondaparinux may be used for anticoagulation prophylaxis in patients hospitalized for oncological purposes, in patients with atrial fibrillation (AF) after resuscitation, in patients with cirrhosis combined with portal vein thrombosis (PVT), in patients with antiphospholipid syndrome (APS), and in patients with inflammatory bowel disease (IBD). Fondaparinux should be used with caution in special populations, such as pregnant female patients with a history of heparin-induced thrombocytopenia (HIT) or platelet counts less than 50 × 109/L, pregnant patients with a prethrombotic state (PTS) combined with recurrent spontaneous abortion (RSA), and children. For bleeding caused by fondaparinux, dialysis may partially remove the drug. Conclusion: The purpose of this guideline is to provide all healthcare providers with high-quality recommendations for the clinical use of fondaparinux and to improve the rational use of the drug in clinical practice. Currently, there is a lack of a dedicated antidote for the management of fondaparinux. The clinical investigation of activated prothrombin complex concentrate (APCC) or recombinant activated factor VII (rFⅦa) as potential reversal agents is still pending. This critical gap necessitates heightened scrutiny and research emphasis, potentially constituting a novel avenue for future inquiries into fondaparinux sodium. A meticulous examination of adverse events and safety profiles associated with the utilization of fondaparinux sodium will contribute significantly to a more comprehensive understanding of its inherent risks and benefits within the clinical milieu.

Engineered therapeutic proteins for sustained-release drug delivery systems

Proteins play a vital role in diverse biological processes in the human body, and protein therapeutics have been applied to treat different diseases such as cancers, genetic disorders, autoimmunity, and inflammation. Protein therapeutics have demonstrated their advantages, such as specific pharmaceutical effects, low toxicity, and strong solubility. However, several disadvantages arise in clinical applications, including short half-life, immunogenicity, and low permeation, leading to reduced drug effectiveness. The structure of protein therapeutics can be modified to increase molecular size, leading to prolonged stability and increased plasma half-life. Notably, the controlled-release delivery systems for the sustained release of protein drugs and preserving the stability of cargo proteins are envisioned as a potential approach to overcome these challenges. In this review, we summarize recent research progress related to structural modifications (PEGylation, glycosylation, poly amino acid modification, and molecular biology-based strategies) and promising long-term delivery systems, such as polymer-based systems (injectable gel/implants, microparticles, nanoparticles, micro/nanogels, functional polymers), lipid-based systems (liposomes, solid lipid nanoparticles, nanostructured lipid carriers), and inorganic nanoparticles exploited for protein therapeutics. STATEMENT OF SIGNIFICANCE: In this review, we highlight recent advances concerning modifying proteins directly to enhance their stability and functionality and discuss state-of-the-art methods for the delivery and controlled long-term release of active protein therapeutics to their target site. In terms of drug modifications, four widely used strategies, including PEGylation, poly amino acid modification, glycosylation, and genetic, are discussed. As for drug delivery systems, we emphasize recent progress relating to polymer-based systems, lipid-based systems developed, and inorganic nanoparticles for protein sustained-release delivery. This review points out the areas requiring focused research attention before the full potential of protein therapeutics for human health and disease can be realized.

Thrombotic Antiphospholipid Syndrome and Direct Oral Anticoagulants: Unmet Needs and Review of the Literature

Patients with thrombotic antiphospholipid syndrome (APS) require long-term anticoagulation due to the high-thrombotic recurrence risk. Vitamin K antagonists (VKA) have been traditionally considered the standard of care in thrombotic APS. Nevertheless, the risk of recurrence persists with VKA. There are publications considering different intensities of anticoagulation with VKA; however, the standard-intensity anticoagulation (international normalized ratio between 2.0 and 3.0) is the most recommended. Furthermore, there is no consensus on the role of antiplatelet treatment in thrombotic APS. Nonvitamin K antagonist oral anticoagulants (NOACs) have emerged as an alternative to VKA for many indications. There are, however, discrepancies regarding the management with NOACs in thrombotic APS. In this review, we update the different clinical trials with NOACs in venous, arterial, and microvascular thrombosis and suggest how these patients should be managed in agreement with the expert panels. Although scarce data are published regarding the current role of NOACs in thrombotic APS, the clinical trials failed to demonstrate noninferiority of NOACs compared with VKA, especially in patients with triple antiphospholipid antibodies positivity and/or arterial thrombosis. Single or double antiphospholipid positivity should be analyzed on a case-by-case basis. In addition, we focus on different areas of uncertainty that still remain in thrombotic APS and NOACs. To summarize, emerging clinical trials are needed to provide robust data on the management of thrombotic APS.

Adrenal hemorrhage and non-ST elevation myocardial infarction: an antiphospholipid syndrome dilemma

Antiphospholipid syndrome (APS) can affect different organ systems, including the heart and adrenal glands. Despite being known for its prothrombotic characteristics, APS can have serious bleeding complications. Occasionally, thrombotic and bleeding episodes can present simultaneously in an APS patient. Whenever these events co-occur, resuming anticoagulation becomes a topic of debate. As such, we present the case of a 43-year-old male with triple positive antiphospholipid antibodies, indicating APS, who presented with chest pain. Anticoagulants were switched one month before presentation from warfarin to a direct oral anticoagulant, rivaroxaban. Non-ST elevation myocardial infarction, as well as new-onset left-sided adrenal hemorrhage, were diagnosed. The patient developed adrenal insufficiency; therefore, corticosteroids were administered, and warfarin was resumed to prevent further thrombotic episodes.

Unprovoked Venous Thromboembolism: The Search for the Cause

Venous thromboembolism (VTE) is a common vascular disorder encompassing deep vein thrombosis (DVT) and pulmonary embolism (PE). There is no data on global estimates of VTE prevalence and incidence. Most patients with unprovoked VTE require secondary thromboprophylaxis upon the completion of the primary treatment phase if they have no high bleeding risk. Risk prediction models can help identify patients at low VTE recurrence risk who may discontinue anticoagulation upon the completion of the primary treatment phase.

Pregnancy outcomes and adverse events in patients with recurrent miscarriage receiving fondaparinux versus low molecular-weight heparin: A meta-analysis

OBJECTIVE

Current opinion on the superiority of fondaparinux versus low molecular-weight heparin (LMWH) in treating recurrent miscarriage is controversial. This meta-analysis aimed to comprehensively compare the pregnancy outcomes and adverse events in patients with recurrent miscarriage receiving fondaparinux versus LMWH.

METHODS

EMBASE, PubMed, Cochrane, China National Knowledge Internet (CNKI), Wanfang Database, and China Science and Technology Journal Database (CQVIP) databases were searched for articles reporting fondaparinux versus LMWH in treating recurrent miscarriage till June 10, 2022. Inclusion criteria for study screening were: (i) randomized, controlled trials (RCT), non-randomized controlled studies, or observational studies; (ii) patients aged over 18 years; (iii) patients with recurrent miscarriage during gestation period; (iv) patients in the experimental/observational group who received FD, and patients in the control group who received LMWH; (v) studies involving at least one outcome of interest for the current analysis. Exclusion criteria were: (i) systematic reviews, meta-analyses, case reports, or animal studies; (ii) duplicated studies; (iii) incomplete or inconsistent data. Quality assessment was conducted with Newcastle-Ottawa Scale criteria or Cochrane Collaboration. Data of live birth, abortion, birth weight, fetal growth restriction (FGR), and adverse events were extracted and synthesized.

RESULTS

Six eligible studies (4 observational studies and 2 RCTs) with 321 patients receiving fondaparinux and 546 patients receiving LMWH were enrolled. Live birth (relative risks (RR) = 1.05, 95% confidence interval (CI) = 0.97 ∼ 1.14, P = 0.217), abortion (RR = 0.73, 95% CI = 0.50 ∼ 1.08, P = 0.113), birth weight (weighted mean difference = 167.20, 95% CI = -236.89 ∼ 571.30, P = 0.417), and FGR (RR = 0.95, 95% CI = 0.25 ∼ 3.59, P = 0.942) were of no difference between patients receiving fondaparinux and LMWH. Regarding adverse events, the incidence of ecchymosis (RR = 0.11, 95% CI = 0.03 ∼ 0.46, P = 0.002) and skin reaction at injection site (RR = 0.15 95% CI = 0.05 ∼ 0.44, P = 0.001) were lower in patients receiving fondaparinux compared with those receiving LMWH, while that of thrombocytopenia (RR = 0.45, 95% CI = 0.09 ∼ 2.14, P = 0.315), vagina bleeding (RR = 1.03, 95% CI = 0.62 ∼ 1.71, P = 0.646), and oral mucosa hemorrhage (RR = 1.08, 95% CI = 0.33 ∼ 3.51, P = 0.899) did not vary between these patients receiving these two treatments. However, most studies were conducted in China, which could induce regional and ethnic bias.

CONCLUSION

Fondaparinux is attributable to fewer adverse events and similar pregnancy outcomes compared with LMWH in patients with recurrent miscarriage.

An update on the biologics for the treatment of antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a systemic autoimmune disease characterized by thrombosis and pregnancy morbidity with the persistent presence of antiphospholipid antibodies (aPLs). Although anticoagulation is the primary treatment for APS, it fails in approximately 20-30% of obstetric APS cases and more than 30% of thrombotic APS cases. Therefore, there is a need for new, targeted treatments beyond anticoagulants. Biologics, such as rituximab and eculizumab, have been recommended for refractory catastrophic APS. This review focuses on the recent advancements in the pathogenesis of APS and explores the potential of targeted treatments, including eculizumab, rituximab, belimumab, daratumumab, obinutuzumab, and anti-TNF-α antibodies, for APS management.

Recurrent embolic strokes due to antiphospholipid syndrome and non-bacterial thrombotic endocarditis in a patient with basal cell carcinoma

BACKGROUND

Non-Bacterial Thrombotic Endocarditis (NBTE) is a common form of aseptic thrombotic endocarditis that primarily affects mitral valves and less frequently aortic valves. NBTE is caused by systemic inflammatory reactions. This condition induces valve thickening or attached sterile mobile vegetation. NBTE is mostly asymptomatic; however, major clinical manifestations result from systemic emboli rather than valve dysfunction. When significant damage occurs, valvular insufficiency or stenosis can appear and promote heart failure occasionally requiring valve replacement surgery. NBTE is associated with hypercoagulable states, systemic lupus erythematous (SLE), antiphospholipid syndrome, or malignancies.

CASE PRESENTATION

We report successful biological aortic valve replacement surgery including cardiopulmonary bypass for a 78-year-old man with NBTE and voluminous vegetation on the aortic valve inducing moderate aortic insufficiency and acute heart failure. The histopathological analysis of the valve sample showed myxoid degeneration, fibrous remodeling, and partial necrosis without any bacteria, thus indicating marantic endocarditis. Initially, the patient presented to the emergency department with an acute stroke. He was already using Apixaban treatment for a history of atrial fibrillation and cardioembolic stroke. Because of the recurrence of stroke and appearance of aortic vegetation, the investigations were extended. The antiphospholipid antibodies were positive without any indication of bacterial endocarditis. The malignancy screening was positive for basal cell carcinoma (BCC). The surgery and postoperative course were uneventful, and the patient was discharged with vitamin K antagonists (VKA). To our knowledge, NBTE with such a volume is rare and its apparent association with BCC has not been previously reported.

CONCLUSION

Outside of SLE and antiphospholipid syndrome, NBTE is a rare and underdiagnosed disease associated with thromboembolic events. Adequate anticoagulation is a cornerstone of its treatment. Anticoagulation management during perioperative care and valve surgery deserves specific attention and helps to protect the patient from embolic complications. In the case of stroke and thromboembolic events of unclear cause or suspected NBTE, echocardiography and thrombophilia assessments including an immunological workup are recommended.

Direct oral anticoagulant adsorption and laboratory detection of lupus anticoagulant

Direct oral anticoagulants (DOACs) interfere with many coagulation assays, mostly in lupus anticoagulant (LA) detection, causing false positive and negative results. Despite guidelines recommendations, LA testing may be important during anticoagulation when the clinician has to decide whether to prolong or discontinue the drug.

OBJECTIVES

In this study, the effect of activated charcoal (DOAC-Stop, DS) as a DOAC-adsorbent was investigated on samples from DOACs treated and untreated patients.

BASIC METHODS

165 plasma samples with a LA request were collected in three laboratories: 105 were from patients receiving DOACs and 60 were from nonanticoagulated patients with 30 LA negative and 30 LA positive. All coagulation screening assays and LA assays were evaluated before and after DS treatment.

RESULTS

The adsorption technique reduced DOACs concentration below the Lower Limit of Quantification. For nonanticoagulated patients: no significant difference in ratio results of coagulation screening (prothrombin time, activated partial thromboplastin time and thrombin time) and LA tests were observed before and after addition of DS in LA positive and negative patients. Every LA was correctly classified. For anticoagulated patients: a statistically significant difference was found for coagulation screening assays and LA assays. Final LA conclusions changed after DS addition from positive to negative in 58.9% of patients (more frequently with Rivaroxaban) and from negative to positive in 8% of patients (more frequently with Apixaban).

CONCLUSIONS

Our study suggests that DOAC-Stop can be used in daily laboratory practice to remove DOACs interference for a more accurate assessment of LA that is essential for diagnosis and management of APS patients.

Interference in point-of-care international normalized ratio monitoring in patients with lupus anticoagulant is correlated with anti-β2-glycoprotein I antibody titers

Background

Patients with antiphospholipid syndrome (APS) receive anticoagulant therapy with vitamin K antagonists (VKAs) to prevent recurrent thrombosis. VKA treatment requires strict monitoring with an international normalized ratio (INR). It is known that lupus anticoagulants (LAs) can lead to elevated INR results with point-of-care-testing (POCT) devices, which could result in inadequate adaptation of anticoagulant therapy.

Objective

To determine discrepancies between POCT-INR and laboratory-INR in patients who are LA-positive on VKA therapy.

Methods

Paired INR testing was performed with 1 POCT device (CoaguChek XS) and 2 laboratory assays (Owren and Quick method) in 33 patients with LA-positive APS on VKA in a single-center cross-sectional study. Patients were tested for anti-β2-glycoprotein I, anticardiolipin, and antiphosphatidylserine/prothrombin immunoglobulin (Ig) G and IgM antibodies. Agreement between assays was evaluated with Spearman's correlation, Lin's correlation coefficient, and Bland-Altman plots. Agreement limits were considered satisfactory if differences were ≤20% as determined by the Clinical and Laboratory Standards Institute.

Results

We found poor agreement between POCT-INR and laboratory-INR based on Lin's concordance correlation coefficient (ρ_c) of 0.42 (95% CI, 0.26-0.55) between POCT-INR and Owren-INR, a ρ_c of 0.64 (95% CI, 0.47-0.76) between POCT-INR and Quick-INR, and a ρ_c of 0.77 (95% CI, 0.64-0.85) between Quick-INR and Owren-INR. High anti-β2-glycoprotein I IgG antibody titers correlated with INR disagreement between POCT-INR and laboratory-INR.

Conclusion

There is a disagreement between INR values measured with the CoaguChek XS and laboratory-INR in a proportion of patients with LA. Consequently, laboratory-INR monitoring should be preferred over POCT-INR monitoring in patients with LA-positive APS, especially in patients with high anti-β2-glycoprotein IgG antibody titers.

Application of anti-Xa assay in monitoring unfractionated heparin therapy in contemporary antithrombotic management

INTRODUCTION

Unfractionated heparin remains the most widely used agent in the prevention and acute treatment of thrombosis. Pharmacological complexities of this intriguing agent mandate frequent monitoring of its anticoagulant properties to maintain safe and effective hematological outcomes. Although activated partial thromboplastin time has been the standard test to monitor unfractionated heparin therapy for many decades, the anti-Xa assay has emerged as a substitute or adjunct in many institutions.

AREAS COVERED

This brief report outlines the key features of anti-Xa assay in monitoring unfractionated heparin in acute management of thrombosis in various contemporary settings, with emphasis on evidence for clinical outcomes. PubMed.gov database was utilized to obtain the pertinent literature.

EXPERT OPINION

The anti-Xa activity is primarily a reflection of UFH concentration and does not account for other hematological variables frequently present in contemporary anticoagulation management. The advantage of the anti-Xa assay in monitoring UFH therapy is predicated upon its limitations to account for global physiological hemostasis. There are significant disease and drug interactions that may potentially result in false in-vitro analysis of anti-Xa activity. Routine application of the anti-Xa assay is not evidence-based at this time.

Research trends and frontiers on antiphospholipid syndrome: A 10-year bibliometric analysis (2012-2021)

Objectives: A growing body of studies related to antiphospholipid syndrome (APS) have been published in recent years. Nevertheless, there is a lack of visualized and systematic analysis in the literature on APS. Hence, this study sought to conduct a bibliometric analysis to identify research status and discover frontiers in the field. Methods: Articles and reviews concerning APS were acquired from the Web of Science Core Collection (WoSCC) database. CiteSpace, VOSviewer and a bibliometric online analysis platform were employed to conduct a visualization and knowledge-map analysis. Results: A total of 1,390 publications regarding APS were identified. Globally, Italy contributed the most publications. The University of Padua was the most productive institution. Lupus ranked first in both the most published and most co-cited journals. Savino Sciascia and Spiros Miyakis were the most prolific and most co-cited authors, respectively. "Vitamin K antagonists (VKA)" and "immunoglobulin A (IgA)" were current research foci. Burst analysis of keywords suggested that "neutrophil extracellular trap (NET)," "direct oral anticoagulant (DOAC)," "open label," "outcome," "hydroxychloroquine (HCQ)," and "arterial thrombosis (AT)" were significant future research frontiers. Conclusion: The scientific literature on APS has increased steadily in the past 10 years. The clinical studies on the treatment and mechanism research of APS are recognized as promising research hotspots in the domain of APS. The research status and trends of APS publications from the bibliometric perspective can provide a practical guide and important reference for subsequent studies by researchers and physicians in the domain.

Direct oral anticoagulants versus warfarin in patients with antiphospholipid syndrome: A meta-analysis of randomized controlled trials

Objective

This study aimed to evaluate the efficacy and safety of direct oral anticoagulants (DOACs) versus warfarin in patients with antiphospholipid syndrome (APS).

Methods

We performed a literature search using MEDLINE, EMBASE, and the Cochrane Controlled Trials Register. We also performed a meta-analysis of randomized controlled trials (RCTs) investigating the effectiveness and safety of DOACs versus warfarin in patients with APS.

Results

Five RCTs involving 648 patients with APS (330 in DOAC-treated and 318 in control groups) were included in the meta-analysis. Among the patients included in the analysis, 29 (8.8%) patients experienced recurrent thrombosis in the DOAC treatment group, and 10 patients (3.1%) had thrombosis recurrence in the warfarin treatment group, resulting in a higher incidence in DOAC-treated than in the warfarin-treated groups [odds ratio (OR) = 2.163, 95% CI = 0.985–4.748, p = 0.055]. Incidence of arterial thrombosis was significantly higher in DOAC-treated patients than in warfarin-treated patients (OR = 5.168, 95% CI = 1.567–17.04, p = 0.007). Stroke and thrombosis occurrences were significantly higher in the triple positivity group than in the warfarin therapy group (OR = 12.03, 95% CI = 2.249–64.36, p = 0.004; OR = 2.940, 95% CI = 1.016–8.504, p = 0.047). However, venous thrombosis occurrences did not differ significantly between the DOAC-treated and warfarin-treated groups. There were no significant differences between the DOAC and warfarin groups in terms of any bleeding, major bleeding, minor bleeding, and all-cause mortality.

Conclusion

DOACs were associated with higher rates of arterial thrombosis than warfarin in patients with APS, especially in the triple-positive group. However, a higher risk of recurrent venous thrombosis was not found in APS patients treated with DOACs compared to those treated with warfarin.

Point of care testing to monitor INR control in patients with antiphospholipid syndrome

Patients with antiphospholipid syndrome (APS) typically require lifelong warfarin anticoagulation following a thrombotic event due to a significant risk of recurrent thrombosis. Point of care testing (POCT) to monitor INR is discouraged in patients with APS as interactions between antiphospholipid antibodies and thromboplastin used for INR testing may influence results. Review of INR testing in 36 APS patients showed 87.2% of paired POCT and venous INRs (n = 94) having acceptable variation (≤0.5 difference), and high correlation (r = 0.9) excluding INRs ≥4.8. Six-month TTR was comparable for APS patients using POCT (57.1% ± 24.8%) to those using venous INR monitoring (59.2% ± 23.2%) (p = 0.66). These results support POCT management of APS but requires further study.

CoaguChek® XS versus standard laboratory prothrombin time for anticoagulant monitoring in patients with antiphospholipid syndrome

INTRODUCTION

The standard of care for thrombotic antiphospholipid syndrome (APS) is anticoagulation with vitamin K antagonists (VKAs). Prothrombin time, and its corresponding international normalized ratio (INR), is the laboratory test routinely performed to assess anticoagulation. Self-management of VKA therapy using point-of-care (POC) devices seems to be an attractive option.

PURPOSE/OBJECTIVE

To evaluate the accuracy of a POC device (CoaguChek XS) in APS patients by comparing it with venous laboratory INR. Furthermore, we analyzed whether other clinical and laboratory features could interfere with the CoaguChek XS results.

PATIENTS AND METHODS

This is a single-center cross-sectional study with 94 APS patients from a tertiary rheumatology clinic performed from August 2014 to March 2015. The comparison between CoaguChek XS and venous laboratory INR results was evaluated using the coefficient of determination (r) followed by the Bland-Altman test. A paired t-test was also applied. A difference of up to ±0.5 INR unit between the two systems was considered clinically acceptable.

RESULTS

The mean CoaguChek-INR was 2.94 ± 1.41 and venous laboratory INR was 2.43±0.86, with a correlation coefficient (r) of 0.95. Categorizing INR values in ranges (INR <2, INR 2-3, INR 3-4, and INR >4), we found that the INR >4 group presented a lower correlation (r = 0.64) compared to the other ranges (p < 0.05). Although both methods were highly correlated, CoaguChek XS showed higher values than the venous laboratory INR, with an increased average of 0.42 ± 0.54. Therefore, we proposed a simple linear regression model to predict the venous laboratory INR values, using results obtained from CoaguChek XS. A difference ≤0.5 INR unit between the two systems was observed in 57.4% of patients, and the aPL profile did not influence the results.

CONCLUSION

Although CoaguChek XS and venous laboratory INR demonstrated a good linear correlation in the group of INR ≤4, extra caution should be taken in APS patients, since a reasonable proportion of patients can present differences in INR results that are not acceptable. We do not recommend routine POC in APS patients.

Snake Venoms in Diagnostic Hemostasis and Thrombosis

Snake venoms have evolved primarily to immobilize and kill prey, and consequently, they contain some of the most potent natural toxins. Part of that armory is a range of hemotoxic components that affect every area of hemostasis, which we have harnessed to great effect in the study and diagnosis of hemostatic disorders. The most widely used are those that affect coagulation, such as thrombin-like enzymes unaffected by heparin and direct thrombin inhibitors, which can help confirm or dispute their presence in plasma. The liquid gold of coagulation activators is Russell's viper venom, since it contains activators of factor X and factor V. It is used in a range of clotting-based assays, such as assessment of factor X and factor V deficiencies, protein C and protein S deficiencies, activated protein C resistance, and probably the most important test for lupus anticoagulants, the dilute Russell's viper venom time. Activators of prothrombin, such as oscutarin C from Coastal Taipan venom and ecarin from saw-scaled viper venom, are employed in prothrombin activity assays and lupus anticoagulant detection, and ecarin has a valuable role in quantitative assays of direct thrombin inhibitors. Snake venoms affecting primary hemostasis include botrocetin from the jararaca, which can be used to assay von Willebrand factor activity, and convulxin from the cascavel, which can be used to detect deficiency of the platelet collagen receptor, glycoprotein VI. This article takes the reader to every area of the diagnostic hemostasis laboratory to appreciate the myriad applications of snake venoms available in diagnostic practice.