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.

D-dimer diagnostics: can I use any D-dimer assay? Bridging the knowledge-to-action gap

A State of the Art lecture titled "D-dimer Diagnostics: Can I use any D-dimer assay? Bridging the Knowledge-to-Action gap" was presented at the International Society on Thrombosis and Haemostasis Congress in 2023, included in the session on the clinical impact of variability in commonly used coagulation assays. Here, we review the role of D-dimer, primarily in the outpatient diagnosis of patients with venous thromboembolism (VTE) when combined with clinical decision rules. We focus on the recent large management trials that have studied adjustments of VTE exclusion thresholds for D-dimer based on either prior clinical probability of VTE or patient age, and the resultant benefit of reduced imaging for VTE and improved diagnostic efficiency. In this context, we report on the significant variability between D-dimer results and the multiple D-dimer assays in use worldwide using data from international external quality assurance programs. This variability is particularly high at typical VTE exclusion thresholds. We discuss the potential clinical impact of D-dimer assay substitution on accuracy of diagnosis and risk stratification of patients with VTE. Finally, we summarize relevant new data on this topic presented during the 2023 International Society on Thrombosis and Haemostasis Congress and outline future priorities urgently needed to harmonize D-dimer results and reporting that will require international collaboration among multiple stakeholders with an overall goal to close this knowledge-to-action gap.

Implementation of the YEARS algorithm to optimise pulmonary embolism diagnostic workup in the emergency department

BACKGROUND

Excessive use of CT pulmonary angiography (CTPA) to investigate pulmonary embolism (PE) in the emergency department (ED) contributes to adverse patient outcomes. Non-invasive D-dimer testing, in the context of a clinical algorithm, may help decrease unnecessary imaging but this has not been widely implemented in Canadian EDs.

AIM

To improve the diagnostic yield of CTPA for PE by 5% (absolute) within 12 months of implementing the YEARS algorithm.

MEASURES AND DESIGN

Single centre study of all ED patients >18 years investigated for PE with D-dimer and/or CTPA between February 2021 and January 2022. Primary and secondary outcomes were the diagnostic yield of CTPA and frequency of CTPA ordered compared with baseline. Process measures included the percentage of D-dimer tests ordered with CTPA and CTPAs ordered with D-dimers <500 µg/L Fibrinogen Equivalent Units (FEU). The balancing measure was the number of PEs identified on CTPA within 30 days of index visit. Multidisciplinary stakeholders developed plan- do-study-act cycles based on the YEARS algorithm.

RESULTS

Over 12 months, 2695 patients were investigated for PE, of which 942 had a CTPA. Compared with baseline, the CTPA yield increased by 2.9% (12.6% vs 15.5%, 95% CI -0.06% to 5.9%) and the proportion of patients that underwent CTPA decreased by 11.4% (46.4% vs 35%, 95% CI -14.1% to -8.8%). The percentage of CTPAs ordered with a D-dimer increased by 26.3% (30.7% vs 57%, 95% CI 22.2% 30.3%) and there were two missed PE (2/2695, 0.07%).

IMPACT

Implementing the YEARS criteria may safely improve the diagnostic yield of CTPAs and reduce the number of CTPAs completed without an associated increase in missed clinically significant PEs. This project provides a model for optimising the use of CTPA in the ED.

Illustrated State-of-the-Art Capsules of the ISTH 2023 Congress

This year's Congress of the International Society of Thrombosis and Haemostasis (ISTH) took place in person in Montréal, Canada, from June 24-28, 2023. The conference, held annually, highlighted cutting-edge advances in basic, translational, population and clinical sciences relevant to the Society. As for all ISTH congresses, we offered a special, congress-specific scientific theme; this year, the special theme was immunothrombosis. Certainly, over the last few years, COVID-19 infection and its related thrombotic and other complications have renewed interest in the concepts of thromboinflammation and immunothrombosis; namely, the relationship between inflammation, infection and clotting. Other main scientific themes of the Congress included Arterial Thromboembolism, Coagulation and Natural Anticoagulants, Diagnostics and Omics, Fibrinolysis and Proteolysis, Hemophilia and Rare Bleeding Disorders, Hemostatic System in Cancer, Inflammation and Immunity, Pediatrics, Platelet Disorders, von Willebrand Disease and Thrombotic Microangiopathies, Platelets and Megakaryocytes, Vascular Biology, Venous Thromboembolism and Women's Health. Among other sessions, the program included 28 State-of-the-Art (SOA) sessions with a total of 84 talks given by internationally recognized leaders in the field. SOA speakers were invited to prepare brief illustrated reviews of their talks that were peer reviewed and are included in this article. These illustrated capsules highlight the major scientific advances with potential to impact clinical practice. Readers are invited to take advantage of the excellent educational resource provided by these illustrated capsules. They are also encouraged to use the image in social media to draw attention to the high quality and impact of the science presented at the Congress.

Quality of anticoagulant control and patient experience associated with long-term warfarin in Canadian patients with non-valvular atrial fibrillation: A multicentre, prospective study

BACKGROUND

Despite the fact that direct oral anticoagulants (DOACs) are favoured over warfarin for stroke prevention in patients with non-valvular atrial fibrillation (NVAF), physicians need to maintain competence in using and monitoring warfarin since many patients have contraindications or other barriers to using DOACs. Unlike DOACs, warfarin therapy requires regular blood testing to ensure that it is within a target range to ensure efficacy and safety. There is limited real-world data on the adequacy of warfarin control and the cost and burden of monitoring warfarin therapy in Canadian NVAF patients.

OBJECTIVES

In a large cohort of Canadian patients with NVAF on warfarin we assessed time in therapeutic range (TTR), determinants of TTR, process of care, direct costs, health related quality of life and loss of work time and productivity related to warfarin therapy.

METHODS

Five hundred and fifty one patients with NVAF, either newly initiated or stable on warfarin were prospectively enrolled across 9 Canadian provinces from primary care practices and anticoagulant clinics. Participating physicians provided baseline demographic and medical information. Patients completed diaries for 48 weeks, capturing information about International Normalized Ratio (INR) test results, test locations, process of INR monitoring, direct costs of travel, health-related quality of life and work productivity measures. TTR was estimated using linear interpolation of INR results and linear regression used to investigate associations between TTR and factors (defined a priori).

RESULTS

Four hundred and eighty (87.1%) patients had complete follow-up with an overall TTR of 74.4% based on 7,175 physician-reported INR values from 501 patients. 88% of this cohort were monitored through routine medical care (RMC). The average number of INRs per patient during the 48-week period was 14.1 (standard deviation (SD) = 8.3) tests with a mean duration of 23.8 (SD = 11.1) days between tests. We did not find a relationship between TTR and age, sex, presence of major comorbidities, patient's province of residence or rural vs. urban residence. 12% of patients monitored through anticoagulant clinics had significantly better TTR than patients monitored through RMC (82% vs. 74%; 95% confidence interval: -13.8, -1.2; p = 0.02). Health related quality of life utility values were high and remained consistent throughout the study. The majority of patients reported no impact on either work productivity or impairment of regular activities due to being on long-term warfarin treatment.

CONCLUSIONS

We showed excellent overall TTR in an observed Canadian cohort, with monitoring through a dedicated anticoagulant clinic being associated with a statistically and clinically significant improvement in TTR. The burden of warfarin therapy on patients' health related quality of life or daily work and activities was low.

Diagnostic Testing for von Willebrand Disease: Trends and Insights from North American Laboratories over the Last Decade

Accurate diagnosis of von Willebrand disease (VWD) depends on the quality, precision, and variability of the laboratory assays. The North American Specialized Coagulation Laboratory Association (NASCOLA) is a provider of external quality assessment (EQA) for approximately 60 specialized coagulation laboratories in North America. In this report, NASCOLA EQA data from 2010 to 2021 are reviewed for trends in methodology and precision among various assays. In particular, recent ASH ISTH NHF WFH (American Society of Hematology, International Society on Thrombosis and Haemostasis, National Hemophilia Foundation, and World Hemophilia Federation) guidelines for diagnosis of VWD are reviewed in light of EQA data. In contrast to other geographic regions, laboratories in North America predominantly use three-assay screening panels (antigen, platelet-binding activity, and factor VIII [FVIII] activity) rather than four-assay panels (antigen, platelet-binding activity, FVIII activity, and collagen-binding activity). They also use latex immunoassays rather than chemiluminescence immunoassays, and the classic ristocetin cofactor (VWF:RCo) assay and monoclonal antibody (VWF:Ab) assay to assess VWF platelet-binding activity over newer recommended assays (VWF:GPIbM and VWF:GPIbR). Factors that may be influencing these North American practice patterns include lack of Food and Drug Administration approval of the VWF:GPIbM, VWF:GPIbR, collagen binding assays, and chemiluminescence methodologies, and the influence of the 2008 National Heart, Lung, and Blood Institute guidelines on laboratory practice. Lastly, systems-based solutions are urgently needed to improve the overall accuracy of laboratory testing for VWD by minimizing preanalytical variables and adopting assay standardization.

Coagulation test understanding and ordering by medical trainees: Novel teaching approach

Background

Coagulation testing provides a prime opportunity to make an impact on the reduction of unnecessary laboratory test ordering, as there are clear indications for testing. Despite the prothrombin time/international normalized ratio and activated partial thromboplastin time being validated for specific clinical indications, they are frequently ordered as screening tests and often ordered together, suggesting a gap in understanding of coagulation.

Methods

Based on a needs assessment, we developed an online educational module on coagulation for trainees, incorporating education on testing cost, specificity, and sensitivity. Fifty participating resident physicians and medical students completed a validated premodule quiz, postmodule quiz after completion of the module, and a latent quiz 3 to 6 months after to assess longer‐term knowledge retention. Trainees provided responses regarding their subjective laboratory test‐ordering practices before and after module completion.

Results

The median premodule quiz score was 67% (n = 50; range, 24%‐86%) with an increase of 24% to a median postmodule quiz score of 91% (n = 50; range, 64%‐100%). There was evidence of sustained knowledge acquisition with a latent quiz median score of 89% (n = 40; range, 67%–100%). Trainees were more likely to consider the sensitivity, specificity, and cost of laboratory investigations before ordering them following completion of the educational module.

Conclusions

Using the expertise of medical educators and incorporating trainee feedback, we employed a novel approach to the teaching of coagulation to maximize its approachability and clinical relevance. We found sustained knowledge retention regarding coagulation and appropriate coagulation test ordering, and a subjective change to trainee ordering habits following participation in our educational intervention.

Effectiveness and safety of the direct oral anticoagulants in non-triple positive antiphospholipid syndrome without prior arterial thromboembolism

Thrombotic antiphospholipid syndrome (TAPS) is an autoimmune disorder that manifests with venous thromboembolism (VTE) and/or arterial thromboembolism (ATE) in the presence of persistent antiphospholipid antibodies (aPLs). Recent trials have failed to demonstrate non-inferiority of the direct oral anticoagulants (DOACs) compared to vitamin K antagonists as anticoagulation in TAPS, but there is a subgroup of non-triple positive patients without prior ATE in who only limited data exists. The objective of this study was to assess the effectiveness and safety of DOACs in non-triple positive TAPS without prior ATE. We conducted a retrospective review of all non-triple positive TAPS patients without prior ATE who were anticoagulated with a DOAC at two tertiary care hospitals from January 2010 to July 2020. We assessed outcomes of VTE, ATE, major bleeding, and clinically relevant non-major bleeding (CRNMB). 50 patients were included in the analysis, encompassing 157.2 years of patient follow-up. There were no recurrent VTE, but one patient had a possible arterial thrombosis (0.64 events per 100 patient-years [95% confidence interval (CI 0.16-35.49)] as a transient ischemic attack (TIA) which occurred on reduced dose DOAC. There were no major bleeding events, but two patients had CRNMB (1.27 events per 100 patient-years [95% CI 1.5-46.0]), both as menorrhagia. DOACs were effective and safe as anticoagulation in non-triple positive TAPS patients without prior ATE with a low rate of recurrent thrombosis and bleeding. Larger, prospective controlled studies are required to confirm these findings prior to routine use of DOACs in this subgroup.

Diagnosis of von Willebrand disease: An assessment of the quality of testing in North American laboratories

BACKGROUND

Laboratory diagnosis of von Willebrand Disease (VWD) is complex. Reliance on laboratory testing can be problematic as different VWD screening panels, assays and methodologies can produce analytic variability in test results.

OBJECTIVES

To compare the degree of imprecision among the VWD assays and within the platelet binding activity (PBA) assays, to determine the consensus among the VWD assays for correct classification of sample results, and to determine consensus among laboratories' von Willebrand factor (VWF) multimer interpretations and final interpretations of the VWD panels.

PATIENTS/METHODS

Proficiency testing results from the North American Specialized Coagulation Laboratory Association (NASCOLA) submitted by laboratories from 2010 to 2019 for all normal, type (T) 1 VWD and T2 VWD samples were analysed.

RESULTS AND CONCLUSIONS

Imprecision was lowest for VWF antigen and highest for collagen binding activity (CBA) with median coefficient of variation (CV) of 12% (interquartile range (IQR) 7%) and 23% (IQR 21%) respectively. Within the VWF PBA assays, the gain-of-function mutant GP1b binding (VWF: GP1bM) methods had the least imprecision (CV 9%, IQR 10%). All assays, including the various PBA methods had excellent consensus. The majority of laboratories agreed that normal (median consensus-82%, IQR 16%) and T1 VWD (median consensus-100%, IQR 9%) samples had normal multimer distribution. Consensus among laboratories for final interpretations was excellent for normal samples (median 81%, IQR 8%), good for T1 VWD samples (median 59%, IQR 9%), and fair for T2 VWD samples (median 44%, IQR 21%). Consensus on final interpretation decreased as sample complexity increased.

Safety of idarucizumab in the reversal of dabigatran at six tertiary care Ontario hospitals

Background

Idarucizumab, a monoclonal antibody fragment that reverses the anticoagulant effect of dabigatran, was approved for use in Canada in 2016.

Objective

Our objective was to assess the safety of idarucizumab among patients who received the drug within the first 3 years of its use in Canada.

Patients/Methods

We performed a retrospective health records review of all idarucizumab use, excluding use in those <18 years of age, between May 16, 2016, and August 1, 2019, at six Ontario tertiary care hospitals. The primary outcome was mortality. The secondary outcomes were in-hospital arterial thrombotic event (ATE), in-hospital venous thromboembolism (VTE), length of hospital stay, and length of critical care stay.

Results

A total of 85 patients received idarucizumab during the study period for the following indications: 37 (43.5%) for spontaneous bleeding, 28 (32.9%) for traumatic bleeding, 11 (12.9%) for emergency surgeries/procedures, 5 (5.9%) for elective surgeries/procedures, and 4 (4.7%) for other indications. Nineteen patients (22.4%; 95% confidence interval [CI], 14.8%-32.3%) did not survive their hospitalization. During hospitalization, two patients (2.4%; 95% CI, 0.7%-8.2%) had ATE, and three patients (3.5%; 95% CI, 1.2%-9.9%) had VTE. The median length of stay was 8 (interquartile range [IQR], 2.5-13) days in hospital and 3 (IQR, 2-5) days in critical care.

Conclusions

Compared with clinical trial data, we found a numerically higher rate of mortality and similar rate of ATE and VTE among patients treated with idarucizumab in the real world.

Impact of specific preclinical variables on coagulation biomarkers in cancer-associated thrombosis

Coagulation biomarkers are being actively studied for their diagnostic and prognostic value in patients with venous thromboembolism and cancer, as well as in the study of pathogenic mechanisms between cancer and thrombosis. For the results of such studies to be accurate and reproducible, attention must be paid to minimize sources of error in all phases of testing. The pre-analytical phase of laboratory testing is known to be fraught with the majority of errors. Coagulation testing is particularly susceptible to conditions during collection, processing, transport and storage of specimens which can lead to clinically significant errors in results. In addition, changes in pre-analytical conditions can impact different biomarkers differently. Therefore, research studies investigating coagulation biomarkers must carefully standardize not just the analytical phase, but also the pre-analytical phase of testing to ensure accuracy and reliability. We briefly review the impact of pre-analytical conditions on coagulation testing in general, and on specific biomarkers in cancer and thrombosis. In addition, we provide recommendations to reduce pre-analytical errors by developing and sharing standard operating procedures that specifically target standardization of methodologies for collecting specimens and measuring current and emerging coagulation biomarkers in cancer studies.

Pseudo Heparin Resistance After Pulmonary Endarterectomy: Role of Thrombus Production of Factor VIII

Pulmonary endarterectomy (PEA) is the main treatment for chronic thromboembolic pulmonary hypertension (CTEPH). Postoperative unfractionated heparin dosing can be monitored by activated partial thromboplastin time (APTT) or by anti-factor Xa activity (anti-Xa). In pseudo heparin resistance, APTT response to heparin is blunted due to elevated Factor VIII (FVIII) which can underestimate anticoagulation. We examined possible pseudo heparin resistance after PEA and assessed the impact of FVIII. APTT response to heparin before and after operation was determined in 13 PEA patients anticoagulated with unfractionated heparin. APTT and anti-Xa concordance was analyzed from paired postoperative samples, and antithrombin, fibrinogen and FVIII levels were measured. Single-cell RNA sequencing was used to characterize FVIII gene expression in PEA specimens of 5 patients. APTT response to heparin was blunted after PEA. APTT and anti-Xa were discordant in 36% of postoperative samples and most common discordant patterns were subtherapeutic APTT with therapeutic (16%) or supratherapeutic (11%) anti-Xa. Overall, APTT underestimated anticoagulation relative to anti-Xa in one-third of the samples. FVIII levels were elevated before surgery, increased substantially 1 and 3 days (median 4.32 IU/mL) after PEA, and were higher in discordant than concordant samples. Single-cell RNA sequencing showed FVIII gene expression in PEA specimen endothelial cells. Pseudo heparin resistance is common after PEA likely due to highly elevated postoperative FVIII levels indicating that anti-Xa reflects postoperative heparinization better than APTT in these patients. FVIII production by the pulmonary artery endothelium may participate in local prothrombotic processes important for CTEPH pathogenesis.

"TEG talk": expanding clinical roles for thromboelastography and rotational thromboelastometry

Viscoelastic assays (VEAs) that include thromboelastography and rotational thromboelastometry add value to the investigation of coagulopathies and goal-directed management of bleeding by providing a complete picture of clot formation, strength, and lysis in whole blood that includes the contribution of platelets, fibrinogen, and coagulation factors. Conventional coagulation assays have several limitations, such as their lack of correlation with bleeding and hypercoagulability; their inability to reflect the contribution of platelets, factor XIII, and plasmin during clot formation and lysis; and their slow turnaround times. VEA-guided transfusion algorithms may reduce allogeneic blood exposure during and after cardiac surgery and in the emergency management of trauma-induced coagulopathy and hemorrhage. However, the popularity of VEAs for other indications is driven largely by extrapolation of evidence from cardiac surgery, by the drawbacks of conventional coagulation assays, and by institution-specific preferences. Robust diagnostic studies validating and standardizing diagnostic cutoffs for VEA parameters and randomized trials comparing VEA-guided algorithms with standard care on clinical outcomes are urgently needed. Lack of such studies represents the biggest barrier to defining the role and impact of VEA in clinical care.

The Cost of Pre-Analytical Errors in INR Testing at a Tertiary-Care Hospital Laboratory: Potential for Significant Cost Savings

BACKGROUND

Preanalytical errors account for most laboratory errors. Although the frequencies of preanalytical errors are well characterized in the literature, little is known regarding the costs of these errors to the laboratory.

OBJECTIVE

To analyze costs associated with preanalytical errors associated with the international normalized ratio (INR) test.

METHODS

We performed a retrospective analysis of INR requests associated with preanalytical error codes from January 2009 through September 2013. Preanalytical error types were those related to order entry (no specimen collected) and those unrelated to order entry (insufficient specimen quantity or specimen-integrity concerns). We calculated the cost of analysis of a specimen and the cost of investigating errors.

RESULTS

During the study period, there were 557,411 INR requests, 13.1% of which were associated with a preanalytical error code. The total annual cost of INR testing was USD $379,222.50. Investigation and reporting of preanalytical errors not related to order entry represented 10.5% of our annual INR testing budget (USD $39,939.00).

CONCLUSIONS

Minimizing preanalytical errors has the potential to result in significant cost savings.

Heparin-induced thrombocytopenia: An international assessment of the quality of laboratory testing

BACKGROUND

Accurate diagnosis of heparin-induced thrombocytopenia (HIT) is essential to ensure timely treatment and prevent complications. Current diagnostic assays include enzyme-linked immunosorbent assays (ELISAs) and rapid immunoassays (RIs). RIs offer fast turnaround times but were not significantly represented in previous external proficiency testing challenges.

OBJECTIVES

To use external proficiency testing to assess qualitative concordance for heparin/PF4 antibody detection.

METHODS

From 2013 to 2017, the External Quality Control for Assays and Tests (ECAT) Foundation distributed 10 samples internationally.

RESULTS

In total, 437 laboratories submitted 3149 results. ELISAs accounted for 1484 (47%) responses with RIs accounting for 1665 (53%) responses. RI use increased over the 5-year period. ELISAs classified 96% of both consensus positive and consensus negative samples concordantly. The coefficient of variation (CV) for positive sample optical densities (ODs) ranged from 35% to 50% when combining ELISA assay methods together. Quantitative RIs classified 97% of consensus-positive and 98% of consensus-negative samples concordantly. Qualitative RIs had a higher proportion of discordant responses and classified 88% of consensus-positive samples and 73% of consensus-negative samples concordantly. Of RIs only latex immunoassays and IgG specific chemiluminescent assays identified > 95% of samples concordantly with consensus.

CONCLUSION

Quantitative RIs and ELISAs classify > 95% of samples concordantly. The ODs from different ELISA methods vary considerably and are not interchangeable. Qualitative RI use is increasing despite a greater proportion of discordant classifications. This includes a higher than expected number of negative classifications for consensus-positive samples among many RIs, challenging their use as "rule out" tests.

Inferior vena cava filter use and patient safety: legacy or science?

There has been a dramatic increase in vena cava filter (VCF) use over the past 20 years in the absence of evidence that filters provide a net patient benefit or are required in most cases. This increase is largely attributable to the availability of retrievable filters and expanded indications, particularly as primary prophylaxis in patients thought to be at high risk of pulmonary embolism. Substantial variability in VCF use, unrelated to patient clinical factors, has been shown between hospitals, from region to region, and among various countries. Despite the lack of direct evidence for the benefit of VCFs for any indication, it is appropriate to insert a retrievable VCF in patients with a recent proximal deep vein thrombosis and an absolute contraindication to therapeutic anticoagulation and then to remove the filter once the bleeding risk decreases and the patient has been anticoagulated. Unfortunately, a high proportion of retrievable filters are not removed, even after the reason for their placement has long passed. Retrievable filters are associated with substantial rates of complications if they are not removed, including penetration of the vena caval wall, fracture and embolization of filter fragments, and caval occlusion. Patient safety priorities and medical-legal concerns mandate careful selection of patients for VCF placement and removal shortly after anticoagulation has been initiated.

Graduated compression stockings to treat acute leg pain associated with proximal DVT

Acute deep venous thrombosis (DVT) causes leg pain. Elastic compression stockings (ECS) have potential to relieve DVT-related leg pain by diminishing the diameter of distended veins and increasing venous blood flow. It was our objective to determine whether ECS reduce leg pain in patients with acute DVT. We performed a secondary analysis of the SOX Trial, a multicentre randomised placebo controlled trial of active ECS versus placebo ECS to prevent the post-thrombotic syndrome.The study was performed in 24 hospital centres in Canada and the U.S. and included 803 patients with a first episode of acute proximal DVT. Patients were randomised to receive active ECS (knee length, 30–40 mm Hg graduated pressure) or placebo ECS (manufactured to look identical to active ECS, but lacking therapeutic compression). Study outcome was leg pain severity assessed on an 11-point numerical pain rating scale (0, no pain; 10, worst possible pain) at baseline, 14, 30 and 60 days after randomisation. Mean age was 55 years and 60% were male. In active ECS patients (n=409), mean (SD) pain severity at baseline and at 60 days were 5.18 (3.29) and 1.39 (2.19), respectively, and in placebo ECS patients (n=394) were 5.38 (3.29) and 1.13 (1.86), respectively. There were no significant differences in pain scores between groups at any assessment point, and no evidence for subgroup interaction by age, sex or anatomical extent of DVT. Results were similar in an analysis restricted to patients who reported wearing stockings every day. In conclusion, ECS do not reduce leg pain in patients with acute proximal DVT.

Two-Generation Oral (Diet) Reproductive Toxicity Study of Resorcinol Bis-Diphenylphosphate (Fyrolflex RDP) in Rats

Fyrolflex resorcinol bis-diphenylphosphate (RDP) was evaluated in a two-generation reproductive study as part of a program to assess the overall toxicology of this flame retardant. RDP was administered to male and female Sprague-Dawley rats in the diet at concentrations of 1000, 10,000 or 20,000 ppm. The control group was given diet alone. Parental (P1) animals were treated for 10 weeks prior to mating, during the 2-week mating period, throughout gestation, and through lactation until sacrifice. The F1 generation (P1 offspring) was treated following a regimen similar to P1. The F2 generation was not treated. No significant difference in Utter survival was observed between the control and treated groups. Body weights were significantly decreased in P1 rats during the 1st week due to an initial flavor aversion of the test substance in the diet. Body weight, weight gains, and food consumption were decreased in the test substance-treated pups (F1) during lactationand after weaning. These changes were also attributed to a flavor aversion. Anogenital distance was similar in the control and high-dose groups, whereas vaginal opening and preputial separation were delayed in the 10,000 and 20,000 ppm groups, and were considered to be secondary to the reduction in F1 body weight. Neither parents nor offspring exhibited any test substance-related clinical signs of toxicity. Vaginal cytology and cyclicity and male reproductive functions (sperm count, motility, and morphology) were unaffected by treatment. Mating performance was similar in the treated groups relative to the control. No treatment-related lesions were noted in the reproductive organs. Increased liver weight and associated hepatic periportal hypertrophy were observed in the RDP-treated animals (P1 and F1). In conclusion, there were no adverse effects on reproductive performance or fertility parameters associated with RDP administration in the diet. Fyrolflex RDP administered for greater than 13 weeks and up to the entire life span (i.e., F1, from conception to euthanasia) resulted in increased liver weights with associated periportal hypertrophy. This change was considered an adaptive process associated with RDP metabolism in the liver.

Assessment of animal African trypanosomiasis (AAT) vulnerability in cattle-owning communities of sub-Saharan Africa

Background

Animal African trypanosomiasis (AAT) is one of the biggest constraints to livestock production and a threat to food security in sub-Saharan Africa. In order to optimise the allocation of resources for AAT control, decision makers need to target geographic areas where control programmes are most likely to be successful and sustainable and select control methods that will maximise the benefits obtained from resources invested.

Methods

The overall approach to classifying cattle-owning communities in terms of AAT vulnerability was based on the selection of key variables collected through field surveys in five sub-Saharan Africa countries followed by a formal Multiple Correspondence Analysis (MCA) to identify factors explaining the variations between areas. To categorise the communities in terms of AAT vulnerability profiles, Hierarchical Cluster Analysis (HCA) was performed.

Results

Three clusters of community vulnerability profiles were identified based on farmers’ beliefs with respect to trypanosomiasis control within the five countries studied. Cluster 1 communities, mainly identified in Cameroon, reported constant AAT burden, had large trypanosensitive (average herd size  = 57) communal grazing cattle herds. Livestock (cattle and small ruminants) were reportedly the primary source of income in the majority of these cattle-owning households (87.0 %). Cluster 2 communities identified mainly in Burkina Faso and Zambia, with some Ethiopian communities had moderate herd sizes (average = 16) and some trypanotolerant breeds (31.7 %) practicing communal grazing. In these communities there were some concerns regarding the development of trypanocide resistance. Crops were the primary income source while communities in this cluster incurred some financial losses due to diminished draft power. The third cluster contained mainly Ugandan and Ethiopian communities which were mixed farmers with smaller herd sizes (average = 8). The costs spent diagnosing and treating AAT were moderate here.

Conclusions

Understanding how cattle-owners are affected by AAT and their efforts to manage the disease is critical to the design of suitable locally-adapted control programmes. It is expected that the results could inform priority setting and the development of tailored recommendations for AAT control strategies.

Combination pretest probability assessment and D-dimer did not reduce outpatient imaging for venous thromboembolism in a tertiary care hospital emergency department

INTRODUCTION

Venous thromboembolism (VTE) is difficult to diagnose yet potentially life threatening. A low-risk pretest probability (PTP) assessment combined with a negative D-dimer can rule out VTE in two-thirds of outpatients, reducing the need for imaging. Real-life implementation of this strategy is associated with several challenges.

METHODS

We evaluated the impact of introducing a standardized diagnostic algorithm including a mandatory PTP assessment and D-dimer on radiologic test use for VTE in our emergency department (ED). A retrospective review of all ED visits for suspected VTE in the year prior to and following the introduction of this algorithm was conducted. VTE diagnosis was based on imaging. Guideline compliance was also assessed.

RESULTS

ED visits were investigated for suspected VTE in the pre- and postintervention periods (n  =  1,785). Most D-dimers (95%) ordered were associated with a PTP assessment, and 50% of visits assigned a low PTP had a negative D-dimer. The proportion of imaging tests ordered for VTE in all ED visits was unchanged postintervention (1.9% v. 2.0%). The proportion of patients with suspected VTE in whom VTE was confirmed on imaging decreased postintervention (10.2% v. 14.1%).

CONCLUSION

In spite of excellent compliance with our algorithm, we were unable to reduce imaging for VTE. This may be due to a lower threshold for suspecting VTE and an increase in investigation for VTE combined with a high false positive rate of our D-dimer assay in low-pretest probability patients. This study highlights two common real-life challenges with adopting this strategy for VTE investigation.

Inflammation markers and their trajectories after deep vein thrombosis in relation to risk of post-thrombotic syndrome

BACKGROUND

Post-thrombotic syndrome (PTS) is a frequent chronic complication of deep vein thrombosis (DVT).

OBJECTIVE

In the BioSOX study, we investigated whether inflammation markers predict the risk of PTS after DVT.

METHODS

We measured C-reactive protein (CRP), ICAM-1, interleukin (IL)-6, and IL-10, at baseline, and 1 month and 6 months after a first proximal DVT, among 803 participants in the SOX trial. Participants were prospectively followed for 24 months for development of PTS.

RESULTS

Median CRP levels at 1 month, ICAM-1 levels at baseline, 1 month and 6 months, IL-6 levels at 1 month and 6 months and IL-10 levels at 6 months were higher in patients who developed PTS than in those who did not. Multivariable regression with the median as a cutoff showed risk ratios (RRs) for PTS of 1.23 (95% confidence interval [CI] 1.05-1.45) and 1.25 (95% CI 1.05-1.48) for ICAM-1 at 1 month and 6 months, respectively, and 1.27 (95% CI 1.07-1.51) for IL-10 at 6 months. Quartile-based analysis demonstrated a dose-response association between ICAM-1 and PTS. ICAM-1 and IL-10 were also associated with PTS severity. Analysis of biomarker trajectories after DVT demonstrated an association between the highest-trajectory group of ICAM-1 and PTS.

CONCLUSIONS

In this prospective study, ICAM-1 over time was most consistently associated with the risk of PTS. Further study is required to confirm these findings and assess their potential clinical relevance.

Symptomatic venous thromboembolism uncommon without thromboprophylaxis after isolated lower-limb fracture: the knee-to-ankle fracture (KAF) cohort study

BACKGROUND

The prevalence of deep vein thrombosis as demonstrated by routine venography in patients with distal lower-extremity injury requiring cast immobilization or surgery is 10% to 40%. These deep vein thromboses are usually asymptomatic and distal, and the need for thromboprophylaxis in these patients is not known.

METHODS

We conducted a multicenter prospective cohort study to define the prevalence of symptomatic venous thromboembolism in patients with a tibial, fibular, or ankle fracture (treated nonoperatively) or a patellar or foot fracture (treated operatively or conservatively). Consecutive patients were enrolled at five Ontario, Canada, hospitals within ninety-six hours after injury, and they were followed with a telephone interview at two, six, and twelve weeks. Thromboprophylaxis was not allowed. Suspected venous thromboembolism was investigated in a standardized manner.

RESULTS

From August 2002 to June 2005, 1200 patients were enrolled, and a three-month follow-up was completed for 98% of them. Eighty-two percent of the patients were treated with cast or splint immobilization for an average (and standard deviation) of 42 ± 32 days. Overall, seven patients (0.6%; 95% confidence interval [CI] = 0.2% to 1.2%) had symptomatic, objectively confirmed venous thromboembolism. Two of them had proximal deep vein thrombosis; three, calf deep vein thrombosis; and two, pulmonary embolism. There were no fatal pulmonary emboli.

CONCLUSIONS

Symptomatic venous thromboembolism is an infrequent complication after fractures of the distal part of the lower limb requiring cast immobilization and managed without thromboprophylaxis. Given these estimates of symptomatic venous thromboembolism, the risk-benefit ratio and cost-effectiveness of routine anticoagulant prophylaxis are unlikely to be favorable for these patients.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Compression stockings to prevent post-thrombotic syndrome: a randomised placebo-controlled trial

BACKGROUND

Post-thrombotic syndrome (PTS) is a common and burdensome complication of deep venous thrombosis (DVT). Previous trials suggesting benefit of elastic compression stockings (ECS) to prevent PTS were small, single-centre studies without placebo control. We aimed to assess the efficacy of ECS, compared with placebo stockings, for the prevention of PTS.

METHODS

We did a multicentre randomised placebo-controlled trial of active versus placebo ECS used for 2 years to prevent PTS after a first proximal DVT in centres in Canada and the USA. Patients were randomly assigned to study groups with a web-based randomisation system. Patients presenting with a first symptomatic, proximal DVT were potentially eligible to participate. They were excluded if the use of compression stockings was contraindicated, they had an expected lifespan of less than 6 months, geographical inaccessibility precluded return for follow-up visits, they were unable to apply stockings, or they received thrombolytic therapy for the initial treatment of acute DVT. The primary outcome was PTS diagnosed at 6 months or later using Ginsberg's criteria (leg pain and swelling of ≥1 month duration). We used a modified intention to treat Cox regression analysis, supplemented by a prespecified per-protocol analysis of patients who reported frequent use of their allocated treatment. This study is registered with ClinicalTrials.gov, number NCT00143598, and Current Controlled Trials, number ISRCTN71334751.

FINDINGS

From 2004 to 2010, 410 patients were randomly assigned to receive active ECS and 396 placebo ECS. The cumulative incidence of PTS was 14·2% in active ECS versus 12·7% in placebo ECS (hazard ratio adjusted for centre 1·13, 95% CI 0·73-1·76; p=0·58). Results were similar in a prespecified per-protocol analysis of patients who reported frequent use of stockings.

INTERPRETATION

ECS did not prevent PTS after a first proximal DVT, hence our findings do not support routine wearing of ECS after DVT.

FUNDING

Canadian Institutes of Health Research.

Evaluation of the warfarin-resistance polymorphism, VKORC1 Asp36Tyr, and its effect on dosage algorithms in a genetically heterogeneous anticoagulant clinic

OBJECTIVES

To assess allele frequency and potential predictive value of recurrent polymorphisms affecting warfarin metabolism in an unselected patient cohort attending an anticoagulant clinic (n=186).

DESIGN AND METHODS

Genotyping of ten SNPs in five candidate genes (VKORC1, CYP2C9, CALU, EPHX and GGCX) was carried out by ABI PRISM SNaPshot multiplex method.

RESULTS

We confirm the association between high-frequency SNPs, VKORC1 c.-1639G>A and CYP2C9 *2/*3 and warfarin sensitivity, and contribute additional evidence that the VKORC1 p.Asp36Tyr variant is recurrent and independently associated with warfarin resistance in our population. Other SNPs made little contribution.

CONCLUSION

Warfarin sensitivity was predicted by known VKORC1 and CYP2C9 SNPs. However, resistance associated with p.Asp36Tyr in VKORC1 would not be predicted by the usual markers. Despite its relatively low frequency (3/186 or 1.6%) clinical considerations may warrant its inclusion in pharmacogenetic screening for initial warfarin dosing in clinic populations with a heterogeneous population base.

The direct medical costs associated with suspected heparin-induced thrombocytopenia

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction associated with heparin exposure. Sunnybrook Health Sciences Centre, a tertiary-care adult academic hospital, has cared for an average of 100 cases of suspected HIT per year. Although the management of suspected HIT is resource intensive, few studies have assessed the cost burden associated with HIT, and none have assessed the costs of suspected HIT.

OBJECTIVE

The objective of this study was to identify and quantify the direct medical costs associated with suspected (confirmed and negative) HIT at a hospital in Canada.

METHODS

A cost-of-illness analysis was conducted in patients with suspected HIT during 2005. Resource utilization variables included (i) laboratory tests to investigate HIT; (ii) HIT-safe anticoagulant use; (iii) diagnostic imaging related to HIT or its treatment; and (iv) additional hospital days attributed to HIT. The average costs per case of confirmed HIT, confirmed HIT with thrombosis (HITT) and negative HIT were calculated in $Can, year 2007 values.

RESULTS

Confirmed HITT cases incurred substantially greater costs ($Can34 155, range 358-202 069; n = 12) than confirmed HIT cases without thrombosis ($Can4575, range 39-16 373; n = 8). The average cost of care for a negative HIT case was $Can119 (range 39-4181; n = 88).

CONCLUSIONS

This is the first study to quantify the costs associated with suspected HIT cases. These cases increase the costs of hospital care and provide further justification for HIT prevention strategies.

Oral vitamin K effectively treats international normalised ratio (INR) values in excess of 10. Results of a prospective cohort study

Unanticipated elevation of the INR is common in patients receiving warfarin. We performed a prospective cohort study of 107 warfarin-treated patients with INR values of more than 10 who received a single 2.5 mg dose of oral vitamin K. During the first week, one patient experienced major bleeding, and one died. In the first 90 days after enrolment four patients had major bleeding (3.7%, 1.0% to 9.3%), eight patients (7.5%, 3.3% to 14.2%) died and two had objectively confirmed thromboembolism. Based on our low rate of observed major bleeding we conclude that 2.5 mg of oral vitamin K is a reasonable treatment for patients with INR values of more than 10 who are not actively bleeding.

Oral vitamin K versus placebo to correct excessive anticoagulation in patients receiving warfarin: a randomized trial

BACKGROUND

Low-dose oral vitamin K decreases the international normalized ratio (INR) in overanticoagulated patients who receive warfarin therapy. Its effects on bleeding events are uncertain.

OBJECTIVE

To see whether low-dose oral vitamin K reduces bleeding events over 90 days in patients with warfarin-associated coagulopathy.

DESIGN

Multicenter, randomized, placebo-controlled trial. Randomization was computer-generated, and participants were allocated to trial groups by using sequentially numbered study drug containers. Patients, caregivers, and those who assessed outcomes were blinded to treatment assignment.

SETTING

14 anticoagulant therapy clinics in Canada, the United States, and Italy.

PATIENTS

Nonbleeding patients with INR values of 4.5 to 10.0.

INTERVENTION

Oral vitamin K, 1.25 mg (355 patients randomly assigned; 347 analyzed), or matching placebo (369 patients randomly assigned; 365 analyzed).

MEASUREMENTS

Bleeding events (primary outcome), thromboembolism, and death (secondary outcomes).

RESULTS

56 patients (15.8%) in the vitamin K group and 60 patients (16.3%) in the placebo group had at least 1 bleeding complication (absolute difference, -0.5 percentage point [95% CI, -6.1 to 5.1 percentage points]); major bleeding events occurred in 9 patients (2.5%) in the vitamin K group and 4 patients (1.1%) in the placebo group (absolute difference, 1.5 percentage points [CI, -0.8 to 3.7 percentage points]). Thromboembolism occurred in 4 patients (1.1%) in the vitamin K group and 3 patients (0.8%) in the placebo group (absolute difference, 0.3 percentage point [CI, -1.4 to 2.0 percentage points]). Other adverse effects were not assessed. The day after treatment, the INR had decreased by a mean of 1.4 in the placebo group and 2.8 in the vitamin K group (P < 0.001).

LIMITATION

Patients who were actively bleeding were not included, and warfarin dosing after enrollment was not mandated or followed.

CONCLUSION

Low-dose oral vitamin K did not reduce bleeding in warfarin recipients with INRs of 4.5 to 10.0.

FUNDING

Canadian Institutes of Health Research and Italian Ministry of Universities and Research.

Experimental infection studies of UK Culicoides species midges with bluetongue virus serotypes 8 and 9

This paper describes a rapid, standardised method for testing the susceptibility to bluetongue virus (BTV) of northern Palaearctic Culicoides species midges that can be used to assess the competence of both field-caught and laboratory-infected midges. The method has been used to show that Culicoides scoticus can replicate btv serotype 8 and BTV serotype 9 strains to more than 3 log(10) TCID50/midge, the first evidence of the potential of this species to transmit BTV.

Prevention of venous thromboembolism: consensus, controversies, and challenges

The last 50 years have witnessed a multitude of publications evaluating the efficacy, safety and cost effectiveness of many different thromboprophylaxis interventions. There is widespread consensus that thromboprophylaxis safely reduces morbidity and mortality. More than 25 evidence-based guidelines, published since 1986, also recommend routine thromboprophylaxis in the majority of hospitalized patients. As a result, thromboprophylaxis is recognized as a key safety priority for hospitals. Some of the remaining areas of controversy that will be discussed in this paper include the role of individual risk assessments to determine thrombosis risk and prophylaxis, replacement of low-dose heparin by low-molecular-weight heparin (LMWH), the optimal duration of prophylaxis, the role of combined thromboprophylaxis modalities, the safety of anticoagulant prophylaxis with regional analgesia, the use of LMWHs in chronic renal insufficiency, and the emerging role of new oral anticoagulants as thromboprophylactic agents. Despite the overwhelming evidence supporting thromboprophylaxis, rates of thromboprophylaxis use remain far from optimal. Successful implementation strategies to bridge this knowledge:care gap are the most important current challenges in this area. These strategies must be multifaceted, utilizing local, systems-based approaches as well as legislation and incentives that reinforce best practices.