An international multicenter randomized study of computer-assisted oral anticoagulant dosage vs. medical staff dosage

Semi-empirical Anticoagulation Model (SAM): Dose prediction during warfarin therapy

Management of oral anticoagulant therapy is essential to ensure a good quality of life for patients. To assist clinicians, several computerized dosing algorithms were developed to determine optimal anticoagulant doses. However, these algorithms have several limitations that can lead to inaccuracies in dosing recommendations. To overcome some of these challenges, this paper proposes a warfarin dose prediction algorithm using individual patient sensitivity analysis. The proposed algorithm is designed to account for factors that influence an individual's response to warfarin, allowing it to more accurately adjust and optimize dosing. It is based on the Semi-empirical Anticoagulation Model (SAM), but has been extended to incorporate stochastic process analysis. This allows the algorithm to assess the probability of events that could change the relationship between the International Normalized Ratio (INR) and the therapy administered. To evaluate the effectiveness of the algorithm, a retrospective observational study of 1796 patients was conducted over one year. The study compared the doses of warfarin administered in clinical practice with those suggested by the algorithm. Percentage Bland-Altman Analysis was used to assess accuracy, which showed that the algorithm had an average accuracy of (3.24±25.80)%. When compared to other algorithms in the literature, which showed an accuracy of (5.73±60.9)%, the proposed algorithm showed significantly better accuracy. The improved accuracy of the proposed algorithm allows for more flexible and precise adjustments to therapy, resulting in an INR closer to the target range with less variability. This ultimately improves patient safety and the overall quality of life for those suffering from venous thromboembolism.

Prosthetic valve dysfunction in patients with mechanical heart valves: Results from the Emergency Salam Centre cohort

INTRODUCTION

Mechanical heart valve (MHV) replacement requires long-life anticoagulation due to the risk of Prosthetic Valve Dysfunction (PVD) and cardioembolism.

METHODS

We report data from a prospective observational study conducted on MHV patients in the Khartoum Salam Centre for Cardiac Surgery built by 'Emergency,' an Italian Non-Governmental Organization, to evaluate the occurrence of PVD and associated risk factors.

RESULTS

We prospectively followed 3647 patients, and 38 patients (rate 1.04 × 100 pt-years) had PVD during follow-up. The time in therapeutic range (TTR) among patients without PVD was 53 % (IQR 37-67), and it was 43 % (IQR 19-58) among patients with PVD (p = 0.04). Twenty-three over 38 patients (60.5 %) were symptomatic, 18 (47.4 %) had obstructive valvular stenosis, 24 patients (63.2 %) had INR <2.0 at diagnosis, and 21 patients (55.3 %) had been off warfarin for a long time: 3 patients for 1 week, 1 patient for 2 weeks, and 17 patients for >4 weeks (6 patients were off warfarin from 3 to 12 months). Ten were uncompliant to treatment, and 8 were pregnant women. Ten patients (26.3 %) with PVD had had a previous episode of PVD, and 14 patients (36.8 %) had 2 or more associated risk factors. Only in 6 cases were no associate risk factors found.

CONCLUSIONS

Among MHV patients on warfarin treatment with a sub-optimal quality of anticoagulation, the rate of PVD is 1.04 % pt-years, and the most frequent associated risk factor for PVD occurrence is warfarin withdrawal lasting more than one week.

Applying a Computer-based Warfarin Management System at a Large Tertiary Cardiovascular Center in Iran

BACKGROUND

Regarding adjustments to warfarin dosage, numerous studies have shown that computerized methods are superior to those based on personal experience.

OBJECTIVES

To report the efficacy of a computer-based warfarin management system (WMS) in the Iranian population.

METHODS

By utilizing the existing dosing algorithms and obtaining expert opinions, we developed a computer-based WMS at a large tertiary cardiovascular center. The time in therapeutic range and the number of international normalized ratio (INR) tests of clinic patients were compared before and after the implementation of WMS.

RESULTS

Overall, 803 patients with 5407 INR tests were included in the before phase and 679 patients with 4189 INR tests in the after phase. The mean time in therapeutic range was 57.3% before and 59% after WMS implementation [mean difference, 1.64; 95% confidence interval (CI), -1.12-4.40]. In the before phase, the mean number of INR tests was 6.7, which dropped to 6.1 tests in the after phase (mean difference, -0.61; 95% CI, -0.97 to -0.24). Only 54.5% of the warfarin dosing prescriptions were consistent with the dosing recommendations of the WMS, and adherence to the WMS was poorest in the highest INR target range.

CONCLUSIONS

For the first time in Iran, we demonstrated that a computerized system was as effective as a traditional experience-based method to monitor INR in VKA-anticoagulated patients. Furthermore, it could reduce both the number of INR tests and that of visits.

Application of eHealth Tools in Anticoagulation Management After Cardiac Valve Replacement: Scoping Review Coupled With Bibliometric Analysis

BACKGROUND

Anticoagulation management can effectively prevent complications in patients undergoing cardiac valve replacement (CVR). The emergence of eHealth tools provides new prospects for the management of long-term anticoagulants. However, there is no comprehensive summary of the application of eHealth tools in anticoagulation management after CVR.

OBJECTIVE

Our objective is to clarify the current state, trends, benefits, and challenges of using eHealth tools in the anticoagulation management of patients after CVR and provide future directions and recommendations for development in this field.

METHODS

This scoping review follows the 5-step framework developed by Arksey and O'Malley. We searched 5 databases such as PubMed, MEDLINE, Web of Science, CINAHL, and Embase using keywords such as "eHealth," "anticoagulation," and "valve replacement." We included papers on the practical application of eHealth tools and excluded papers describing the underlying mechanisms for developing eHealth tools. The search time ranged from the database inception to March 1, 2023. The study findings were reported according to the PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews). Additionally, VOSviewer (version 1.6.18) was used to construct visualization maps of countries, institutions, authors, and keywords to investigate the internal relations of included literature and to explore research hotspots and frontiers.

RESULTS

This study included 25 studies that fulfilled the criteria. There were 27,050 participants in total, with the sample size of the included studies ranging from 49 to 13,219. The eHealth tools mainly include computer-based support systems, electronic health records, telemedicine platforms, and mobile apps. Compared to traditional anticoagulation management, eHealth tools can improve time in therapeutic range and life satisfaction. However, there is no significant impact observed in terms of economic benefits and anticoagulation-related complications. Bibliometric analysis suggests the potential for increased collaboration and opportunities among countries and academic institutions. Italy had the widest cooperative relationships. Machine learning and artificial intelligence are the popular research directions in anticoagulation management.

CONCLUSIONS

eHealth tools exhibit promise for clinical applications in anticoagulation management after CVR, with the potential to enhance postoperative rehabilitation. Further high-quality research is needed to explore the economic benefits of eHealth tools in long-term anticoagulant therapy and the potential to reduce the occurrence of adverse events.

Association of sex with major bleeding risks in sub-Saharian anticoagulated patients with mechanical heart valves: A cohort study from the Khartoum Emergency Salam Centre

BACKGROUND

Rheumatic heart disease (RHD) with mechanical heart valve (MHV) replacement is common in Africa. However, MHV requires lifelong anticoagulation that could have a particular impact in women in reproductive age.

METHODS

We report data of a prospective observational cohort study conducted between August 2018 and September 2019 in MHV patients in the Salam Centre for Cardiac Surgery built in Khartoum by Emergency, an Italian Non-Governmental Organization, to evaluate bleeding risk, its associated determinants, and the impact of lifelong anticoagulation in fertile women.

RESULTS

We studied 3647 patients (median age 25.1 years; 53.9% female). During follow-up [median time 1.1 (0.1-1.2) years], we recorded 85 major bleedings (rate 2.16 × 100 pt-years), Major bleedings occurred more frequently among women (64/85 cases, 75.3%; rate 3.0 × 100 pt-years), compared to men (21/85 cases, 24.7%; rate 1.16 × 100 pt-years) (RR 2.6; 95% CI 1.6-4.5; p = 0.0001). Multivariate analysis was performed to identify variables associated with major bleeding, and female sex was the only risk factor significantly associated, whereas aspirin treatment and higher INR target showed a non-significant trend for higher bleeding risk. Thirty-two/85 (37.6%) of major bleedings were metrorrhagias. When we calculate the incidence of major bleedings after the exclusion of gynecological events, no sex differences in the bleeding risk were found (HR 1.3, 95% CI 0.8-2.3; p = 0.3).

CONCLUSIONS

Bleeding risk of young MHV patients on oral anticoagulant therapy is higher among women, mainly due to metrorrhagia. Women in the reproductive life are at high risk for gynecological bleeding when treated with anticoagulants.

Telemedicine-based management of oral anticoagulation therapy: a systematic review and meta-analysis (Preprint)

BACKGROUND

Oral anticoagulation is the cornerstone treatment of several diseases. Its management is often challenging, and different telemedicine strategies have been implemented to support it.

OBJECTIVE

The aim of the study is to systematically review the evidence on the impact of telemedicine-based oral anticoagulation management compared to usual care on thromboembolic and bleeding events.

METHODS

Randomized controlled trials were searched in 5 databases from inception to September 2021. Two independent reviewers performed study selection and data extraction. Total thromboembolic events, major bleeding, mortality, and time in therapeutic range were assessed. Results were pooled using random effect models.

RESULTS

In total, 25 randomized controlled trials were included (n=25,746 patients) and classified as moderate to high risk of bias by the Cochrane tool. Telemedicine resulted in lower rates of thromboembolic events, though not statistically significant (n=13 studies, relative risk [RR] 0.75, 95% CI 0.53-1.07; I²=42%), comparable rates of major bleeding (n=11 studies, RR 0.94, 95% CI 0.82-1.07; I²=0%) and mortality (n=12 studies, RR 0.96, 95% CI 0.78-1.20; I²=11%), and an improved time in therapeutic range (n=16 studies, mean difference 3.38, 95% CI 1.12-5.65; I²=90%). In the subgroup of the multitasking intervention, telemedicine resulted in an important reduction of thromboembolic events (RR 0.20, 95% CI 0.08-0.48).

CONCLUSIONS

Telemedicine-based oral anticoagulation management resulted in similar rates of major bleeding and mortality, a trend for fewer thromboembolic events, and better anticoagulation quality compared to standard care. Given the potential benefits of telemedicine-based care, such as greater access to remote populations or people with ambulatory restrictions, these findings may encourage further implementation of eHealth strategies for anticoagulation management, particularly as part of multifaceted interventions for integrated care of chronic diseases. Meanwhile, researchers should develop higher-quality evidence focusing on hard clinical outcomes, cost-effectiveness, and quality of life.

TRIAL REGISTRATION

PROSPERO International Prospective Register of Systematic Reviews CRD42020159208; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=159208.

Oral anticoagulant management of patients with mechanical heart valves at the Salam Centre of Khartoum: Observations on quality of anticoagulation and thrombotic risk

INTRODUCTION

Rheumatic heart disease with mechanical heart valve (MHV) replacement is common in Africa. However, MHV requires long-life anticoagulation and managing this can be challenging.

METHODS AND RESULTS

We report data of a prospective observational study conducted between August 2018 and September 2019 in MHV patients in the Salam Centre for Cardiac Surgery built in Khartoum, by Emergency, an Italian Non-Governmental Organization, to evaluate the quality of anticoagulation control and the risk of thrombotic complications.

RESULTS

We studied 3647 patients (median age 25.1 years; 53.9 % female). Median Time in Therapeutic Range (TTR) was 53 % (interquartile range 37 % to 67 %) and 70 thrombotic events (rate 1.8 × 100 pt-years [95 % CI 1.38-2.23]) were recorded. Among patients in the first quartile of TTR (≤37 %), we recorded 34/70 (48.6 %) of all thrombotic events (rate 3.7 × 100 pt-years [95 % CI 2.5-5.1]), with a high mortality rate (2.2 × 100 pt-years [95 % CI 1.3-3.3]). In patients with guideline-recommended TTR (≥65 %) the event rate was 0.8 × 100 pt-years for thrombotic events [95 % CI 0.3-1.5] and 0.4 × 100 pt-years for mortality [95 % CI 0.1-0.9]. Multivariable analysis showed that having a TTR in the lowest quartile (≤37 %) and being noncompliant are significantly associated with increased thrombotic risk. Aspirin use or different valve type did not influence the thrombotic risk. Almost 40 % of all thromboembolic complications could have been potentially prevented by further improving VKA management to obtain a TTR > 37 %.

CONCLUSION

The thrombotic risk of MHV patients on VKAs living in a low-income country like Sudan is associated with low quality of anticoagulation control. Efforts should be made to decrease the number of non-compliant patients and to reach a guideline-recommended TTR of ≥65 %.

Deep Venous Thrombosis

Venous thromboembolism (VTE) is the third most common cardiovascular disorder, affecting up to 5% of the population. VTE commonly manifests as lower-extremity deep venous thrombosis (DVT) or pulmonary embolism. Half of these events are associated with a transient risk factor and may be preventable with prophylaxis. Direct oral anticoagulants are effective and safe and carry a lower risk for bleeding than vitamin K antagonists. Many patients with VTE will have a chronic disease requiring long-term anticoagulation. Postthrombotic syndrome affects 25% to 40% of patients with DVT and significantly impacts function and quality of life.

Validation and comparison between two warfarin dosing clinical algorithms and warfarin fixed dosing in specialized heart center: cross-sectional study

Background

Warfarin is well known as a narrow therapeutic index that has prodigious variability in response which challenges dosing adjustment for the maintenance of therapeutic international normalized ratio. However, an appreciated population not on new oral anticoagulants may still need to be stabilized with warfarin dosing.

Objective

The current study's main objective was to validate and compare two models of warfarin clinical algorithm models namely the Gage and the International Warfarin Pharmacogenetics Consortium (IWPC) with warfarin 5 mg fixed standard dosing strategy in a sample of Sudanese subjects.

Method

We have conducted a cross-sectional study recruited from the out-patient clinic at a tertiary specialized heart center. We included subjects with unchanged warfarin dose (stabilized), and with therapeutic international normalized ratio. The predicted doses of warfarin in the two models were calculated by three different methods (accuracy, clinical practicality, and the clinical safety of the clinical algorithms).

Main outcome measure

The primary outcomes were the measurements of the clinical (accuracy, practicality, and safety) in each of the two clinical algorithms models compared to warfarin 5 mg fixed standard dose strategy.

Results

We have enrolled 71 Sudanese subjects with mean age (51.7 ± 14 years), of which (49, 69.0%) were females. There was no significant difference between the warfarin 5 mg fixed standard dose strategy and the predicted doses of the two clinical algorithm models (MAE 1.44, 1.45, and 1.49 mg/day [P =0.4]) respectively. In the clinical practicality, all of the three models had a high percent of subjects (95.0%, 51.9%, and 66.7%) in the ideal dose range in middle dose group (3-7 mg/ day) for warfarin 5 mg fixed standard dosing strategy, Gage, and IWPC clinical algorithm models respectively. However, a small percent of subjects was exhibited in the warfarin low dose group ≤ 3 mg/day (0.0%, 15.0%, and 10.0%) and warfarin high dose group ≥ 7 mg/day (0.0%, 33.3%, and 33.3%) for warfarin 5 mg fixed standard dosing strategy, Gage, and IWPC clinical algorithms respectively. In terms of clinical safety, the percent of subjects with severely over-prediction were 28.2%, 22.5%, and 22.5% for warfarin 5 mg fixed standard dosing, Gage, and IWPC, respectively. While the percent of severely under-prediction was 12.7%, 7.0%, and 5.6% for the warfarin 5 mg fixed standard dosing, Gage, and IWPC, respectively.

Conclusion

The Gage and IWPC clinical algorithm models were accurate, more clinically practical, and clinically safe than warfarin 5 mg standard dosing in the study population. The cardiologist can use either models (Gage and IWPC) to stratify subjects for accurate, practical, and clinically safe warfarin dosing..

Development and validation of a mobile application based on a machine learning model to aid in predicting dosage of vitamin K antagonists among Indian patients post mechanical heart valve replacement

Patients who undergo heart valve replacements with mechanical valves need to take Vitamin K Antagonists (VKA) drugs (Warfarin, Nicoumalone) which has got a very narrow therapeutic range and needs very close monitoring using PT-INR. Accessibility to physicians to titrate drugs doses is a major problem in low-middle income countries (LMIC) like India. Our work was aimed at predicting the maintenance dosage of these drugs, using the de-identified medical data collected from patients attending an INR Clinic in South India. We used artificial intelligence (AI) - machine learning to develop the algorithm. A Support Vector Machine (SVM) regression model was built to predict the maintenance dosage of warfarin, who have stable INR values between 2.0 and 4.0. We developed a simple user friendly android mobile application for patients to use the algorithm to predict the doses. The algorithm generated drug doses in 1100 patients were compared to cardiologist prescribed doses and found to have an excellent correlation.

Evaluating warfarin dosing models on multiple datasets with a novel software framework and evolutionary optimisation

Warfarin is an effective preventative treatment for arterial and venous thromboembolism, but requires individualised dosing due to its narrow therapeutic range and high individual variation. Many machine learning techniques have been demonstrated in this domain. This study evaluated the accuracy of the most promising algorithms on the International Warfarin Pharmacogenetics Consortium dataset and a novel clinical dataset of South African patients. Support vectors and linear regression were amongst the top performers in both datasets and performed comparably to recent stacked ensemble approaches, whilst neural networks were one of the worst performers in both datasets. We also introduced genetic programming to automatically optimise model architectures and hyperparameters without human guidance. Remarkably, the generated models were found to match the performance of the best models hand-crafted by human experts. Finally, we present a novel software framework (Warfit-learn) for warfarin dosing research. It leverages the most successful techniques in preprocessing, imputation, and parallel evaluation, with the goal of accelerating research and making results in this domain more reproducible.

Patient compliance with an anticoagulation management system based on a smartphone application

We developed a novel anticoagulation management system (Anticlot Assistant) based on a smartphone application (App). This study was performed to evaluate patient compliance with Anticlot Assistant. This prospective case series study involved patients receiving warfarin therapy. The eligible patients were managed via Anticlot Assistant, and outcome data were analyzed. Thirty patients were recruited. The mean time within the therapeutic range (TTR) was 56.5% ± 26.2% and the mean patient compliance with Anticlot Assistant was 52.7% ± 40.4%. The patients in good compliance group had higher TTR (65.6 ± 25.0% vs. 40.0 ± 21.0%, P = 0.009), lower time in the extremely low range (9.4 ± 10.6% vs. 27.4 ± 13.2%, P = 0.000) and in the extremely high range (1.3 ± 2.8% vs. 14.1 ± 22.3%, P = 0.004) than those in poor compliance group. Logistic regression analysis revealed that receiving an education of > 6 years was the only independent predictor of good compliance (odds ratio 8.400, 95% confidence interval 1.274-55.394, P = 0.027). Patient compliance is critical important for good outcomes and it might increase with improvements in education and more widespread use of information technology. Although further improvement is needed, Anticlot Assistant is promising and this study offered valuable experiences for further research.

Providers' utilization and perceptions of warfarin dosing algorithms

INTRODUCTION

Warfarin dosing algorithms have proven beneficial in increasing time within therapeutic range (TTR) and decreasing adverse events associated with out-of-range international normalized ratios (INRs). Despite widespread availability, providers' utilization and perceptions of warfarin algorithms in real-world practice are unclear. Identifying perceptions and barriers to algorithm use may help attempts to improve warfarin therapy management.

METHODS

Anticoagulation providers' utilization and perceptions of warfarin dosing algorithms were assessed via a nationwide electronic survey.

RESULTS

Of the 246 providers who completed the survey, 82% were pharmacists, and 69% had over five years' experience dosing warfarin. Warfarin dosing algorithms were deemed beneficial by 84% of respondents and 72% currently use a warfarin dosing algorithm in their practice at least occasionally. Pharmacists were least likely of anticoagulation providers to use algorithms, although this was not statistically significant (p = 0.12). Algorithm utilization also decreased as years of warfarin dosing experience increased, with the highest rate of usage noted in the first year of dosing warfarin. The most common reason providers gave for discontinuing algorithm use was that they no longer felt it was needed. In this study, clinic patient volume did not appear to be associated with algorithm utilization.

CONCLUSION

Warfarin dosing algorithms are frequently used among anticoagulation providers, especially those new to dosing warfarin, but use is frequently not sustained over the long-term. Education on the continued benefits of warfarin dosing algorithms could increase long-term utilization, potentially improving patient outcomes.

An Assessment of the Effectiveness of Warfarin Therapy Monitoring Systems on Thrombophilic Patients in Zimbabwe

Introduction  Thrombophilia describes conditions that predispose individuals to increased blood clotting and includes conditions such as deep vein thrombosis and pulmonary embolism. Thrombophilia is associated with high morbidity and mortality rates, and is commonly treated by warfarin anticoagulation. However, warfarin may cause both bleeding and clotting episodes if the therapy is not monitored and managed effectively.

Objectives  The main objective of this study was to assess the effectiveness of warfarin monitoring systems on thrombophilic patients at a major hospital in Zimbabwe.

Material and Methods  A clinical and laboratory prospective and retrospective study was performed on patients who had been on warfarin therapy for at least 1 year. Questionnaires were administered to participants on warfarin from outpatients clinics at Parirenyatwa Group of Hospitals. Their international normalized ratio (INR) results were also accessed from the laboratory information system and captured in the Epi info and Microsoft Excel for analysis.

Results  Fifty questionnaires were administered and 47 (94%) participants responded adequately. Twenty-nine (61.1%) participants on warfarin were females. The majority of them were elderly and in the 31 to 40 age groups. Eighteen (38.3%) participants missed their medication at some point, while 12 (25.5%) had warfarin overdose. Sixteen (34%) and 11 (23.4%) admitted to taking alcohol and smoking, respectively, while on warfarin. Thirty-five (74.5%) did not change their medication nor were advised on the right diet. Thirty-four (72.3%) had appointments set after every month. Some participants indicated that they had symptoms of both clotting and bleeding. There were statistically significant differences ( p  < 0.0001) between INRs for 3 monthly intervals from the initiation of warfarin therapy.

Conclusion  Women and the elderly formed the majority of the patients on warfarin, indicating gender and advanced age susceptibility to thrombophilia, respectively. The effectiveness of the warfarin monitoring systems appeared to be hampered by lack of a coordinated system that adequately monitors anticoagulant therapy in the country.

Recommendations for the post-operative management of an existing Warfarin therapy after lower limb joint arthroplasty

BACKGROUND

Warfarin administration after lower limb joint replacements is associated with a high bleeding risk, creating the circumstances for periprosthetic joint infections, increased treatment costs and prolonged Length of Stay (L.o.S). We believe that previously warfarinized patients can be treated safely and discharged without delays, if appropriate policies are established and adhered to.

METHODS

This is a retrospective cohort study. We have collected and analyzed data from an audit cycle between 2012 and 2015 on: 1) the post-operative Warfarin reloading protocol, identifying 4 distinct patterns: usual dose, 1.5 times or double the usual dose for 2 days and overloading, 2) timing of reloading: Evening of Surgery vs post-op Day 1, 3) frequency of INR testing: daily vs intermittent, 4) time required to reach a therapeutic INR value ≥2.0, 5) rate of INR variations ≥4.0 and 6) bleeding complications, 7) and the overall L.o.S.

RESULTS

We found a significant difference in the time required to reach an INR ≥2.0 between reloading with the usual dose and all other protocols (p < 0.001) without abolishing adverse sequelae. Daily INR testing reduced bleeding complications and INR variations at a significant (p < 0.001) and non-significant level respectively, while timing of restarting showed no significant effect. We found a correlation between INR variations and bleeding complications (odds ratio: 4.65, C.I: 0.59-30.87). 41% of the cohort was discharged on the day their INR turned therapeutic with an average L.o.S of 6.5 days.

CONCLUSION

We recommend to: 1) restart Warfarin at double (or in exceptional cases 1.5 times) the patient's maintenance dose for the first two doses, 2) starting on the Evening of Surgery, 3) with daily INR monitoring after the second loading dose, 4) using point of care testing devices, 5) and dosing thereafter to be guided by an anticoagulation service or computer assistance.

Bleeding with anticoagulant treatments

Anticoagulation with vitamin K antagonists (VKAs) is effective in the prevention and treatment of thrombotic complications in many clinical conditions, including atrial fibrillation (that represents today the most frequent indication for anticoagulant treatment), venous thromboembolism, acute coronary syndromes and after invasive cardiac procedures. Bleeding is the most important complication of VKAs and a major concern for both physicians and patients, limiting a more widespread prescription of the treatment. As a result, a non negligible proportion of all the subjects who would have a clear clinical indication for anticoagulation do not receive an effective treatment.

This review analyses the treatment- and person-associated risk factors for bleeding during VKAs. New oral anticoagulant drugs seems to overcome at least some of the limitations of VKAs. Potentially, they can allow a less demanding and more stable anticoagulant treatment, with less side-effects allowing that more patients can receive an appropriate anticoagulant treatment. Based on the so far available phase III clinical studies, it is possible to assume that these new drugs are associated with a risk of bleeding, that is probably related to the intensity of treatment.

Randomised comparison of a simple warfarin dosing algorithm versus a computerised anticoagulation management system for control of warfarin maintenance therapy

Excellent control of the international normalised ratio (INR) is associated with improved clinical outcomes in patients receiving warfarin, and can be achieved by anticoagulation clinics but is difficult in general practice. Anticoagulation clinics have often used validated commercial computer systems to manage the INR, but these are not usually available to general practitioners. It was the objective of this study to perform a randomised trial of a simple one-step warfarin dosing algorithm against a widely used computerised dosing system. During the period of introduction of a commercial computerised warfarin dosing system (DAWN AC) to an anticoagulation clinic, patients were randomised to have warfarin dose adjustment done according to recommendations of the existing warfarin dosing algorithm or to those of the computerised system. The study tested if the computerised system was non-inferior to the existing algorithm for the primary outcome of time in therapeutic INR range of 2.0–3.0 (TTR), with a one-sided non-inferiority margin of 4.5%. There were 541 patients randomised to commercial computerised system and 527 to the algorithm. Median follow-up was 159 days. A dose recommendation was provided and followed in 91% of occasions for the computerised system and in 90% for the algorithm (p=0.03). The mean TTR was 71.0% (standard deviation [SD] 23.2) for the computerised system and 71.9% (SD 22.9) for the algorithm (difference 0.9% [95% confidence interval: –1.4% to 4.1%];p-value for noninferiority=0.002;p-value for superiority=0.34). In conclusion, similar maintenance control of the INR was achieved with a simple one-step dosing algorithm and a commercial computerised management system.

Cessation of oral anticoagulation in relation to mortality and the risk of thrombotic events in patients with atrial fibrillation

Bleeding risk (often perceived, rather than actual) is a common reason for cessation of oral anticoagulation with Vitamin K antagonists (VKA). We investigate clinical outcomes in a consecutive population of VKA naïve atrial fibrillation (AF) patients, who initiated VKA therapy in our clinic. We included consecutive VKA-naíve patients with non valvular AF, initiated on VKA therapy in our anticoagulation outpatient clinic in 2009. During follow-up, adverse events [thrombotic/vascular events (stroke, acute coronary syndrome, acute heart failure and cardiac death), major bleeding and death], and VKA cessation were recorded. At the end of the follow-up, we determined time within therapeutic range (TTR), using a linear approximation (Rosendaal method). We studied 529 patients (49% male, median age 76), median follow-up 835 days (IQR 719−954). During this period 114 patients stopped VKA treatment. 63 patients suffered a thrombotic/cardiovascular event (5.17%/year, 27 thrombotic/ischaemic strokes), 51 major bleeding (4.19%/year) and 48 died (3.94%/year). Median TTR was 54% (34a57). On multivariate analysis (adjusted by CHA2DS2-VASc score), VKA cessation was associated with death [Hazard Ratio (HR) 3.43; p<0.001], stroke [4.21; p=0.001] and thrombotic/cardiovascular events [2.72; p<0.001]. Independent risk factors for major bleeding were age [1.08; p<0.001], previous stroke [1.85; p=0.049], and TTR [0.97; p=0.001], but not VKA cessation. In conclusion, in AF patients AF, VKA cessation is independently associated with mortality stroke and cardiovascular events. Specifically, VKA cessation independently increased the risk of stroke, even after adjusting for CHA2DS2-VASc score. TTR was an independent risk factor for major bleeding following initiation of VKA therapy.

Note: The editorial process for this paper was fully handled by Prof Christian Weber, Editor in Chief.

How well do general practitioners manage laboratory test results for patients with diabetes mellitus and cardiovascular disease?: A systematic review

Purpose

To evaluate how well general practitioners (GPs) manage and respond to laboratory results for patients with diabetes mellitus (DM) and cardiovascular disease (CVD).

Data sources

MEDLINE, CINAHL, Embase, EBM reviews, ProQuest and Scopus.

Study selection

Peer-reviewed journal articles published between 2000 and 2015 that assessed GPs' management of laboratory results for patients with DM or CVD.

Data extraction

Study design and demographics, laboratory tests and key findings relating to GP management of laboratory results were extracted from studies.

Results of data synthesis

Thirteen articles were included, comprising seven studies which utilized surveys, four observational studies, one cohort study and one randomized controlled trial. Findings indicate that GPs often overestimate the risk of complications associated with DM and CVD based on laboratory results and have unrealistically high expectations regarding the precision of laboratory tests. Considerable variation existed in the use of repeat testing for diagnostic confirmation and in GPs' identification of the difference between two consecutive results required to indicate a change in patient condition. GPs also often failed to initiate appropriate treatment for patients with DM and CVD based on laboratory results. Feedback to GPs about their test ordering patterns and educational messages on laboratory results improved clinical outcomes.

Conclusion

Evidence about how well GPs manage results and its impact on patient outcomes remains weak and inconclusive. This review identified a number of areas where interventions could support GPs to improve the interpretation and management of laboratory test results, including feedback to GPs and educational messages on test result reports.

The Effects of Computerized Clinical Decision Support Systems on Laboratory Test Ordering: A Systematic Review

CONTEXT

- Inappropriate laboratory test ordering has been shown to be as high as 30%. This can have an important impact on quality of care and costs because of downstream consequences such as additional diagnostics, repeat testing, imaging, prescriptions, surgeries, or hospital stays.

OBJECTIVE

- To evaluate the effect of computerized clinical decision support systems on appropriateness of laboratory test ordering.

DATA SOURCES

- We used MEDLINE, Embase, CINAHL, MEDLINE In-Process and Other Non-Indexed Citations, Clinicaltrials.gov, Cochrane Library, and Inspec through December 2015. Investigators independently screened articles to identify randomized trials that assessed a computerized clinical decision support system aimed at improving laboratory test ordering by providing patient-specific information, delivered in the form of an on-screen management option, reminder, or suggestion through a computerized physician order entry using a rule-based or algorithm-based system relying on an evidence-based knowledge resource. Investigators extracted data from 30 papers about study design, various study characteristics, study setting, various intervention characteristics, involvement of the software developers in the evaluation of the computerized clinical decision support system, outcome types, and various outcome characteristics.

CONCLUSIONS

- Because of heterogeneity of systems and settings, pooled estimates of effect could not be made. Data showed that computerized clinical decision support systems had little or no effect on clinical outcomes but some effect on compliance. Computerized clinical decision support systems targeted at laboratory test ordering for multiple conditions appear to be more effective than those targeted at a single condition.

Patient knowledge of anticoagulant treatment does not correlate with treatment quality

OBJECTIVES

The objectives of this study were to investigate whether patient knowledge is a predictor of treatment stability in anticoagulant clinic patients and to evaluate the correlation between the patients' subjective assessment of own knowledge and their score on a validated knowledge assessment instrument.

STUDY DESIGN

This is a prospective study where international normalized ratio (INR) stability was followed up 6 months after knowledge assessment.

METHODS

We analyzed data of 42 consecutive patients new to vitamin-K antagonist (VKA) treatment and 64 experienced patients from an anticoagulant clinic offering patient education. The patients filled out a VKA knowledge assessment questionnaire with 24 items under standardized conditions, and simultaneously, they were asked about their subjective knowledge. Subsequently, time in range of INR (TIR) was collected for each patient.

RESULTS

Out of the 106 patients, 52 had 18 or more correct answers (>75%), defined as a 'satisfactory level' of objective knowledge. The average TIR was 73%, and treatment stability was significantly higher in experienced patients than new patients. We found no correlation between objective knowledge and TIR (Spearman rho = -0.03, P = 0.78). Most patients (77%) reported a high subjective knowledge of VKA, but no correlation was found between objective and subjective knowledge (Spearman rho = 0.129, P = 0.19).

CONCLUSION

We observed that many patients had a low level of knowledge of VKA, despite high treatment stability and patient education. The patient's own assessment of knowledge was not found to predict objective knowledge, which could have implications for selection of patients for self-test or self-management of treatment.

The safety and efficacy of vitamin K antagonist in atrial fibrillation patients with previous ulcer bleeding: Long-term results from a multicenter study

This study aimed to evaluate the safety and efficacy of vitamin K antagonist (VKA) in atrial fibrillation (AF) patients with previous ulcer bleeding.In this multicenter, retrospective analysis, clinical outcomes of 754 AF patients with a history of ulcer bleeding were evaluated. After ulcer treatment, 458 patients (61%) were treated with VKA, and the outcomes were compared to 296 patients (39%) without VKA.VKA treatment significantly increased major bleeding (7.3%/year vs 3.2%/year, P < 0.001), and reduced major adverse cardiac events (MACE) (5.4%/year vs 10.0%/year, P < 0.001). Specifically, risk of gastrointestinal bleeding was significantly higher in the VKA group than no-VKA group (5.7%/year vs 2.6%/year, P < 0.001). Consequently, there was no difference in the incidence of composite of a MACE and major bleeding, between the 2 groups. In patients with time in the therapeutic range (TTR) ≥65%, VKA significantly decreased MACE (2.8%/year vs 10.0%/year, P < 0.001) without increasing major bleeding. Net clinical benefit model showed beneficial effects of VKA in patients with TTR ≥65%, and harmful effects in those with TTR < 55%.In AF patients with previous ulcer bleeding, VKA treatment did not improve clinical outcomes unless the international normalized ratio level was constantly maintained (TTR ≥65%), as the gastrointestinal bleeding (GIB) risk significantly increased.

Guidance for the practical management of warfarin therapy in the treatment of venous thromboembolism

Venous thromboembolism (VTE) is a serious and often fatal medical condition with an increasing incidence. The treatment of VTE is undergoing tremendous changes with the introduction of the new direct oral anticoagulants and clinicians need to understand new treatment paradigms. This article, initiated by the Anticoagulation Forum, provides clinical guidance based on existing guidelines and consensus expert opinion where guidelines are lacking. Well-managed warfarin therapy remains an important anticoagulant option and it is hoped that anticoagulation providers will find the guidance contained in this article increases their ability to achieve optimal outcomes for their patients with VTE Pivotal practical questions pertaining to this topic were developed by consensus of the authors and were derived from evidence-based consensus statements whenever possible. The medical literature was reviewed and summarized using guidance statements that reflect the consensus opinion(s) of all authors and the endorsement of the Anticoagulation Forum’s Board of Directors. In an effort to provide practical and implementable information about VTE and its treatment, guidance statements pertaining to choosing good candidates for warfarin therapy, warfarin initiation, optimizing warfarin control, invasive procedure management, excessive anticoagulation, subtherapeutic anticoagulation, drug interactions, switching between anticoagulants, and care transitions are provided.

Anti-Xa bioassays for the laboratory measurement of direct Factor Xa inhibitors in plasma, in selected patients

In the past decade Direct Oral Anti-Coagulants (DOACs), targeting Thrombin or Factor Xa, have enormously facilitated the daily treatment of all relevant patients, including those requiring lifelong therapy. These DOACs have considerable advantages over the use of oral Vitamin K Antagonist (VKA) treatments, in view of having little interferences with food and other medications and also not requiring adjustment for age, gender or weight, with some well-defined exceptions. In this current What's Happening Section we focus on measurements of DiXaIs in plasma using anti-Xa assays, with the objective of providing a tribute to Professor Michel Meyer Samama, who was not only a real leader in this field but, in the past, both authors benefited from his wisdom, as a teacher who dedicated his scientific and professional life (among many other interests in hemostasis, thrombosis and fibrinolysis) to develop and promote methods and strategies for laboratory monitoring of anticoagulants. This review presents the performance characteristics of the Anti-Factor Xa assays (measuring Factor Xa inhibition by drugs), which are available for measuring Direct Factor Xa Inhibitors in plasma, and show good compliance of the results with the reference LC:MS method (which measures the mass of Direct Factor Xa Inhibitors). We also present the preparation and validation of drug specific plasma calibrators and controls which are requested for drug measurements. These assays are convenient and practical laboratory tools which can be used in any laboratory setting, and meet the requirements of regulatory bodies for making smart, quantitative, sensitive, accurate and ease of use assays for measuring DOACs when needed. The manuscript focuses mainly on the following areas of current interest: interference in coagulation assays; anti-Xa laboratory methods; development of calibrators and controls for DiXaIs; method validation and comparison with reference techniques (LC:MS); regulatory requirements and method registrations; newer clinical applications and experience on DiXaIs with Anti-Xa assays, and future perspectives.

Vitamin K antagonist use: evidence of the difficulty of achieving and maintaining target INR range and subsequent consequences

Vitamin K antagonists (VKAs) are effective oral anticoagulants that are titrated to a narrow therapeutic international normalized ratio (INR) range. We reviewed published literature assessing the impact of INR stability - getting into and staying in target INR range - on outcomes including thrombotic events, major bleeding, and treatment costs, as well as key factors that impact INR stability.

A time in therapeutic range (TTR) of ≥65 % is commonly accepted as the definition of INR stability. In the real-world setting, this is seldom achieved with standard-of-care management, thus increasing the patients’ risks of thrombotic or major bleeding events. There are many factors associated with poor INR control. Being treated in community settings, newly initiated on a VKA, younger in age, or nonadherent to therapy, as well as having polymorphisms of CYP2C9 or VKORC1, or multiple physical or mental co-morbid disease states have been associated with lower TTR. Clinical prediction tools are available, though they can only explain <10 % of the variance behind poor INR control.

Clinicians caring for patients who require anticoagulation are encouraged to intensify diligence in INR management when using VKAs and to consider appropriate use of newer anticoagulants as a therapeutic option.

Warfarin Dosing Algorithms and the Need for Human Intervention

BACKGROUND

Dosing algorithms for warfarin incorporate clinical and genetic factors, but human intervention to overrule algorithm-based dosing may occasionally be required. The frequency and reasons for varying from algorithmic warfarin management have not been well studied.

METHODS

We analyzed a prospective cohort of 1015 participants from the Clarification of Optimal Anticoagulation through Genetics trial who were randomized to either pharmacogenetic- or clinically-guided warfarin dosing algorithms. Clinicians and participants were blinded to dose but not international normalized ratio (INR) during the first 28 days. If an issue arose that raised concern for clinicians but might not be adequately accounted for by the protocol, then clinicians contacted the unblinded medical monitor who could approve exceptions if clinically justified. All granted exceptions were logged and categorized. We analyzed the relationships between dosing exceptions and both baseline characteristics and the outcome of percentage of time in the therapeutic INR range during the first 4 weeks.

RESULTS

Sixteen percent of participants required at least one exception to the protocol-defined warfarin dose (15% in the genotype arm and 17% in the clinical arm). Ninety percent of dose exceptions occurred after the first 5 days of dosing. The only baseline characteristic associated with dose exceptions was congestive heart failure (odds ratio 2.12, 95% confidence interval, 1.49-3.02, P <.001). Neither study arm nor genotype was associated with dose exceptions.

CONCLUSION

Despite rigorous algorithms, human intervention is frequently employed in the early management of warfarin dosing. Congestive heart failure at baseline appears to predict early exceptions to standardized protocol management.

Effective and Safe Management of Oral Anticoagulation Therapy in Patients Who Use the Internet-Accessed Telecontrol Tool SintromacWeb

Background

Despite the existing evidence that highlights the benefits of oral anticoagulation therapy (OAT) self-testing and self-management by patients in comparison with conventional control, significant progress is still needed in the implementation of computer-based, Internet-assisted systems for OAT within health care centers. The telecontrol tool “SintromacWeb” is a previously validated system for OAT management at home, which is currently operative and accessed by patients through a hospital Web portal.

Objective

The intent of the study was to assess the effectiveness and safety of OAT management in patients using the SintromacWeb telecontrol system in reference to control in patients using the conventional system (management at the hematology department), in terms of time in therapeutic range (TTR) of International Normalized Ratio (INR).

Methods

In this observational prospective study, patients were identified by their physician and divided in two groups according to the OAT management system that they were already using (conventional control or telecontrol with SintromacWeb). For 6 months, patients were required to visit the hematology department every time their physician considered it necessary according to usual clinical practice. Sociodemographic and clinical variables for the study were collected at first visit (baseline) and at those visits closest to 2, 4, and 6 months after first visit.

Results

A total of 173 patients were evaluated, 87 with conventional control and 86 with telecontrol. Follow-up time was a median of 6.3 (range 5.2-8.1) months. The average time of OAT treatment prior to enrollment was 9.2 (SD 6.4) years. Patients in the telecontrol group tested their INR a median of 21 (range 4-22) days versus a median of 35 (range 14-45) days in patients in the conventional control group (P<.001). TTR in the telecontrol group was 107 (SD 37) days versus 94 (SD 37) days in the conventional control group (an increase of 12.6%; P=.02). In all visits, the percentage of TTR was higher in the telecontrol group (at the third visit: 59% vs 48%; P=.01). Higher TTR (positive coefficient) was associated with patients under OAT telecontrol (P=.03). Under-anticoagulation (INR<1.5) and over-anticoagulation (INR>5) were observed in 34 (19.7%, 34/173) and 38 (22.0%, 38/173) patients, respectively (no differences between treatment groups). Seven thrombotic and/or bleeding events were serious, 12 were non-serious, and most of them (5 and 10, respectively) occurred in the conventional control group.

Conclusions

In clinical practice, OAT management with the Internet-based tool SintromacWeb is effective and safe for those patients who are eligible for OAT telecontrol.

PGWD: integrating personal genome for warfarin dosing

Warfarin is a drug normally used in the prevention of thrombosis and the formation of blood clots. The dosage of warfarin is strongly affected by genetic variants of CYP2C9 and VKORC1 genes. Current technologies for detecting the variants of these genes are mainly based on real-time PCR. In recent years, due to the rapidly dropping cost of whole genome sequencing and genotyping, more and more people get their whole genome sequenced or genotyped. However, current software for warfarin dosing prediction is based on low-throughput genetic information either from real-time PCR, or melting curve methods. There is no bioinformatics tool available that can take the high-throughput genome sequencing data as input and determine the accurate dosage of warfarin. Here, we present PGWD, a web tool that analyzes personal genome sequencing data, and integrates with clinical information for warfarin dosing.

Quality of oral anticoagulation with phenprocoumon in regular medical care and its potential for improvement in a telemedicine-based coagulation service--results from the prospective, multi-center, observational cohort study thrombEVAL

BACKGROUND

The majority of studies on quality of oral anticoagulation (OAC) therapy with vitamin K-antagonists are performed with short-acting warfarin. Data on long-acting phenprocoumon, which is frequently used in Europe for OAC therapy and is considered to enable more stable therapy adjustment, are scarce. In this study, we aimed to assess quality of OAC therapy with phenprocoumon in regular medical care and to evaluate its potential for optimization in a telemedicine-based coagulation service.

METHODS

In the prospective observational cohort study program thrombEVAL we investigated 2,011 patients from regular medical care in a multi-center cohort study and 760 patients from a telemedicine-based coagulation service in a single-center cohort study. Data were obtained from self-reported data, computer-assisted personal interviews, and laboratory measurements according to standard operating procedures with detailed quality control. Time in therapeutic range (TTR) was calculated by linear interpolation method to assess quality of OAC therapy. Study monitoring was carried out by an independent institution.

RESULTS

Overall, 15,377 treatment years and 48,955 international normalized ratio (INR) measurements were analyzed. Quality of anticoagulation, as measured by median TTR, was 66.3% (interquartile range (IQR) 47.8/81.9) in regular medical care and 75.5% (IQR 64.2/84.4) in the coagulation service (P <0.001). Stable anticoagulation control within therapeutic range was achieved in 63.8% of patients in regular medical care with TTR at 72.1% (IQR 58.3/84.7) as compared to 96.4% of patients in the coagulation service with TTR at 76.2% [(IQR 65.6/84.7); P = 0.001)]. Prospective follow-up of coagulation service patients with pretreatment in regular medical care showed an improvement of the TTR from 66.2% (IQR 49.0/83.6) to 74.5% (IQR 62.9/84.2; P <0.0001) in the coagulation service. Treatment in the coagulation service contributed to an optimization of the profile of time outside therapeutic range, a 2.2-fold increase of stabile INR adjustment and a significant decrease in TTR variability by 36% (P <0.001).

CONCLUSIONS

Quality of anticoagulation with phenprocoumon was comparably high in this real-world sample of regular medical care. Treatment in a telemedicine-based coagulation service substantially improved quality of OAC therapy with regard to TTR level, frequency of stable anticoagulation control, and TTR variability.

TRIAL REGISTRATION

ClinicalTrials.gov, unique identifier NCT01809015, March 8, 2013.

An audit of anticoagulant management to assess anticoagulant control using decision support software

OBJECTIVE

To evaluate the effectiveness of a computerised self-adjusting anticoagulant algorithm to predict appropriate warfarin dosing and to assess its use in clinical practice.

DESIGN

A 3-year audit of anticoagulant control in patients managed by doctors and pharmacists using computer decision support and an evaluation of the impact of dose adjustments made by the users.

PARTICIPANTS

3660 patients on oral anticoagulants; one-third of patients managed by doctors and two-thirds by pharmacists.

SETTING

Anticoagulant supervision in primary care and pharmacies at 60 sites in New Zealand.

MAIN OUTCOME MEASURES

The time in the therapeutic range (TTR), the outcome of adherence to the computer dosing algorithm, the percentage of time the clinicians over-ride the algorithm and the impact of their intervention on anticoagulant control.

RESULTS

A TTR of 72.9% was achieved for all patients. The TTR was significantly better in patients managed by pharmacists than doctors (75.1% versus 67.4%, p<0.0001). The computer algorithm provides appropriate dose recommendations for INR results from 1.5 to 4. Users administered a dose that differed from the computer recommendation 23.3% of the time. The doctors adjusted the dose more frequently (28.2% versus 21.1% of tests) and made larger dose changes than the pharmacists.

CONCLUSIONS

The clinicians predominantly change the dose when the INR is below the therapeutic range. The changes are not necessary to correct for inaccuracies in the algorithm. The most likely explanation is the clinician's belief that their own dose adjustment would achieve better control; however, in practice, their changes tend to underdose patients. The doctors achieved poorer control than the pharmacists; this is in part due to the action of the doctors over-riding the algorithm. Our results imply that clinicians could achieve better anticoagulant control if they more closely followed the computer algorithm.

Predicting anticoagulant-related bleeding in patients with venous thromboembolism: a clinically oriented review

Diagnosis of venous thromboembolism (VTE) requires prompt treatment with anticoagulants in therapeutic doses. Since these drugs are associated with the occurrence of haemorrhage, identification of patients at increased risk of major bleeding is of utmost clinical importance for defining the optimal treatment regimen and duration of anticoagulation. Current suggested prediction scores for bleeding risk in VTE patients have been derived from observational studies of moderate quality, or from patients with various indications for therapeutic anticoagulation other than VTE. To date, none of the scores have been adequately validated in cohorts that underwent dedicated monitoring and independent adjudication of bleeding complications. In addition, while the scarce available evidence has focused on patients treated with heparins and/or vitamin K antagonists, risk stratification scores for bleeding complications in VTE patients treated with non-vitamin K dependent anticoagulants have not yet been developed. This clinically oriented review covers the incidence and risk factors of anticoagulation-related bleeding in VTE patients treated with different anticoagulant drugs as well as the available bleeding-prediction scores. Further, we attempt to provide guidance for bleeding-prevention in clinical practice and speculate on developments in the near future that may fundamentally change our current thinking on VTE management.

Warfarin or dabigatran for treatment of atrial fibrillation

BACKGROUND

New antithrombotic drugs for prevention and treatment of thromboembolic disorders in AF that are less demanding on local staff and facilities than warfarin should be welcomed if proved successful.

OBJECTIVES

The comparative value and possible dangers of substituting the new drug dabigatran as a replacement remain to be established. Its safety and effectiveness must be reviewed and assessed by further study.

METHODS

Clinical results of the European Action on Anticoagulation (EAA) computer-assisted dosage study and the Randomized Evaluation of Long-Term Anticoagulation Therapy (RE-LY) trial have been compared.

RESULTS

Clinical events were lower in patients on warfarin in the EAA study compared to patients on both warfarin and dabigatran in the RE-LY study.

CONCLUSION

Evaluations should recognize optimum requirements for safe and effective administration of both types of drug. In the warfarin arm improvements in effectiveness and safety recently introduced (i.e. the PT/INR line and variance growth analysis) should be included as they have been shown to be successful in improved prediction of bleeding and further thromboembolism. The incidence of bleeding with dabigatran, for which there is no antidote, will require evaluation.

Quality of vitamin K antagonist control and outcomes in atrial fibrillation patients: a meta-analysis and meta-regression

BACKGROUND

Atrial fibrillation (AF) patients frequently require anticoagulation with vitamin K antagonists (VKAs) to prevent thromboembolic events, but their use increases the risk of hemorrhage. We evaluated time spent in therapeutic range (TTR), proportion of international normalized ratio (INR) measurements in range (PINRR), adverse events in relation to INR, and predictors of INR control in AF patients using VKAs.

METHODS

We searched MEDLINE, CENTRAL and EMBASE (1990-June 2013) for studies of AF patients receiving adjusted-dose VKAs that reported INR control measures (TTR and PINRR) and/or reported an INR measurement coinciding with thromboembolic or hemorrhagic events. Random-effects meta-analyses and meta-regression were performed.

RESULTS

Ninety-five articles were included. Sixty-eight VKA-treated study groups reported measures of INR control, while 43 studies reported an INR around the time of the adverse event. Patients spent 61% (95% CI, 59-62%), 25% (95% CI, 23-27%) and 14% (95% CI, 13-15%) of their time within, below or above the therapeutic range. PINRR assessments were within, below, and above range 56% (95% CI, 53-59%), 26% (95% CI, 23-29%) and 13% (95% CI, 11-17%) of the time. Patients receiving VKA management in the community spent less TTR than those managed by anticoagulation clinics or in randomized trials. Patients newly receiving VKAs spent less TTR than those with prior VKA use. Patients in Europe/United Kingdom spent more TTR than patients in North America. Fifty-seven percent (95% CI, 50-64%) of thromboembolic events and 42% (95% CI, 35 - 51%) of hemorrhagic events occurred at an INR <2.0 and >3.0, respectively; while 56% (95% CI, 48-64%) of ischemic strokes and 45% of intracranial hemorrhages (95% CI, 29-63%) occurred at INRs <2.0 and >3.0, respectively.

CONCLUSIONS

Patients on VKAs for AF frequently have INRs outside the therapeutic range. While, thromboembolic and hemorrhagic events do occur patients with a therapeutic INR; patients with an INR <2.0 make up many of the cases of thromboembolism, while those >3.0 make up many of the cases of hemorrhage. Managing anticoagulation outside of a clinical trial or anticoagulation clinic is associated with poorer INR control, as is, the initiation of therapy in the VKA-naïve. Patients in Europe/UK have better INR control than those in North America.

Measures of vitamin K antagonist control reported in atrial fibrillation and venous thromboembolism studies: a systematic review

OBJECTIVE

To aid trialists, systematic reviewers and others, we evaluated the degree of standardisation of control measure reporting that has occurred in atrial fibrillation (AF) and venous thromboembolism (VTE) studies since 2000; and attempted to determine whether the prior recommendation of reporting ≥2 measures per study has been employed.

DESIGN

Systematic review.

SEARCH STRATEGY

We searched bibliographic databases (2000 to June 2013) to identify AF and VTE studies evaluating dose-adjusted vitamin K antagonists (VKAs) and reporting ≥1 control measure. The types of measures reported, proportion of studies reporting ≥2 measures and mean (±SD) number of measures per study were determined for all studies and compared between subgroups.

DATA EXTRACTION

Through the use of a standardised data extraction tool, we independently extracted all data, with disagreements resolved by a separate investigator.

RESULTS

148 studies were included, 57% of which reported ≥2 control measures (mean/study=2.13±1.36). The proportion of time spent in the target international normalised ratio range (TTR) was most commonly reported (79%), and was frequently accompanied by time above/below range (52%). AF studies more frequently reported ≥2 control measures compared with VTE studies (63% vs 37%; p=0.004), and reported a greater number of measures per study (mean=2.36 vs 1.53; p<0.001). Observational studies were more likely to provide ≥2 measures compared with randomised trials (76% vs 33%; p<0.001) and report a greater number of measures (mean=2.58 vs 1.63; p<0.001). More recent studies (2004-2013) reported ≥2 measures more often than older (2000-2003) studies (59% vs 35%; p=0.05) and reported more measures per study (mean=2.23 vs 1.48; p=0.02).

CONCLUSIONS

While TTR was often utilised, studies reported ≥2 measures of VKA control only about half of the time and lacked consistency in the types of measures reported. A trend towards studies reporting greater numbers of VKA control measures over time was observed over our review time horizon, particularly, with AF and observational studies.

[Computer aided dosage management of phenprocoumon anticoagulation therapy. Clinical validation]

A recently developed multiparameter computer-aided expert system (TheMa) for guiding anticoagulation with phenprocoumon (PPC) was validated by a prospective investigation in 22 patients. The PPC-INR-response curve resulting from physician guided dosage was compared to INR values calculated by "twin calculation" from TheMa recommended dosage. Additionally, TheMa was used to predict the optimal time to perform surgery or invasive procedures after interruption of anticogulation therapy.

RESULTS

Comparison of physician and TheMa guided anticoagulation showed almost identical accuracy by three quantitative measures: Polygon integration method (area around INR target) 616.17 vs. 607.86, INR hits in the target range 166 vs. 161, and TTR (time in therapeutic range) 63.91 vs. 62.40 %. After discontinuation of anticoagulation therapy, calculating the INR phase-out curve with TheMa INR prognosis of 1.8 was possible with a standard deviation of 0.50 ± 0.59 days.

CONCLUSION

Guiding anticoagulation with TheMa was as accurate as Physician guided therapy. After interruption of anticoagulant therapy, TheMa may be used for calculating the optimal time performing operations or initiating bridging therapy.

[Anticoagulation clinics, present situation and future perspectives]

There are several modalities to monitor oral anticoagulant therapy, namely: monitoring by a secondary care specialist in the hospital setting; monitoring by the general practitioner/ family doctor in the primary care setting; monitoring by private laboratories of clinical analysis; self-monitoring with point-of-care devices. In Portugal, the most frequent modality is still the hospital monitoring/anticoagulation clinics, although monitoring in the primary care/routine medical care setting has began to be implemented in some areas of the country since five years ago. Anticoagulation clinics are still actually the organizations that optimize better the clinical and laboratorial follow up of the patients anticoagulated with warfarin. In 2011, anticoagulation control quality was evaluated, in the setting of an anticoagulation clinic (Santo António Hospital, Porto Hospital Center) by determining the proportion of INRs within the therapeutic range. The evaluation focused ambulatory patients, during a period of two months, corresponding to 1067 controls from 687 patients (mean age: 69±13 years; 54%, n=567, female gender). 71% of controls (n=756) were within the therapeutic range. 27% of controls were outside the therapeutic range, after exclusion of patients with programmed surgery or invasive proceedings. 13.8% of controls were below the therapeutic range and 8.6% (n=92) of the latter had INR ≤ 1.5. Above therapeutic range were 13.2% (n=139), from which 4.4% (n=46) had an INR between 5-8 and 0.3% (n=4) an INR ≥ 8. The group of primary care Health Centers (Portuguese acronym ACES) of the Baixo Tâmega region conducted, also in 2011, an evaluation of the anticoagulant control quality, by determining the proportion of INRs within the therapeutic range. The results were similar to those found in the anticoagulation clinic of the Hospital de Santo António which shows that the quality of monitoring in the primary care setting can have the same quality of the anticoagulation clinics monitoring. The introduction of the new oral anticoagulants, that don't require laboratorial monitoring constitutes a challenge. In Portugal, there is no experience yet to respond to the question if, in this new context, the anticoagulation clinics will be fundamental for the registration of patients, the evaluation of the hemorrhagic risk, the clinical follow up or the evaluation of the adherence to therapy.

The effectiveness of computerized drug-lab alerts: a systematic review and meta-analysis

BACKGROUND

Inadequate lab monitoring of drugs is a potential cause of ADEs (adverse drug events) which is remediable.

OBJECTIVES

To determine the effectiveness of computerized drug-lab alerts to improve medication-related outcomes.

DATA SOURCES

Citations from the Computerized Clinical Decision Support System Systematic Review (CCDSSR) and MMIT (Medications Management through Health Information Technology) databases, which had searched MEDLINE, EMBASE, CINAHL, Cochrane Database of Systematic Reviews, International Pharmaceutical Abstracts from 1974 to March 27, 2013.

STUDY SELECTION

Randomized controlled trials (RCTs) of clinician-targeted computerized drug lab alerts conducted in any healthcare setting. Two reviewers performed full text review to determine study eligibility.

DATA ABSTRACTION

A single reviewer abstracted data and evaluated validity of included studies using Cochrane handbook domains.

DATA SYNTHESIS

Thirty-six studies met the inclusion criteria (25 single drug studies with 22,504 participants, 14 targeting anticoagulation; 11 multi-drug studies with 56,769 participants). ADEs were reported as an outcome in only four trials, all targeting anticoagulants. Computerized drug-lab alerts did not reduce ADEs (OR 0.89, 95% CI 0.79-1.00, p=0.05), length of hospital stay (SMD 0.00, 95%CI -0.93 to 0.93, p=0.055, 1 study), likelihood of hypoglycemia (OR 1.29, 95% CI 0.31-5.37) or likelihood of bleeding, but were associated with increased likelihood of prescribing changes (OR 1.73, 95% CI 1.21-2.47) or lab monitoring (OR 1.47, 95% confidence interval 1.12-1.94) in accordance with the alert.

CONCLUSIONS

There is no evidence that computerized drug-lab alerts are associated with important clinical benefits, but there is evidence of improvement in selected clinical surrogate outcomes (time in therapeutic range for vitamin K antagonists), and changes in process outcomes (lab monitoring and prescribing decisions).

Improvement of anticoagulant treatment using a dynamic decision support algorithm: a Danish Cohort study

INTRODUCTION

Warfarin is the most widely prescribed vitamin K antagonist and in the United States and Europe more than 10 million people are currently in long-term oral anticoagulant treatment. This study aims to retrospectively validate a dynamic statistical model providing dosage suggestions to patients in warfarin treatment.

MATERIALS AND METHODS

The model was validated on a cohort of 553 patients with a mean TTR of 83%. Patients in the cohort were self-monitoring and managed by a highly specialised anticoagulation clinic. The predictive model essentially consists of three parts handling INR history, warfarin dosage and biological noise, which allows for prediction of future INR values and optimal warfarin dose to stay on INR target. Further, the model is based on parameters initially being set to population values and gradually individualised during monitoring of patients.

PRIMARY OUTCOME

Time in therapeutic range was used as surrogate quality measure of the treatment, and model-suggested dosage of warfarin was used to assess the accuracy of the model performance.

RESULTS

The accuracy of the model predictions measured as median absolute error was 0.53 mg/day (interquartile range from 0.25 to 1.0). The model performance was evaluated by the difference between observed and predicted warfarin intake in the preceding week of an INR measurement. In more than 70% of the cases where INR measurements were outside the therapeutic range, the model suggested a more reasonable dose than the observed intake.

CONCLUSION

Applying the proposed dosing algorithm can potentially further increase the time in INR target range beyond 83%.

Vitamin K antagonists in heart disease: current status and perspectives (Section III). Position paper of the ESC Working Group on Thrombosis--Task Force on Anticoagulants in Heart Disease

Oral anticoagulants are a mainstay of cardiovascular therapy, and for over 60 years vitamin K antagonists (VKAs) were the only available agents for long-term use. VKAs interfere with the cyclic inter-conversion of vitamin K and its 2,3 epoxide, thus inhibiting γ-carboxylation of glutamate residues at the amino-termini of vitamin K-dependent proteins, including the coagulation factors (F) II (prothrombin), VII, IX and X, as well as of the anticoagulant proteins C, S and Z. The overall effect of such interference is a dose-dependent anticoagulant effect, which has been therapeutically exploited in heart disease since the early 1950s. In this position paper, we review the mechanisms of action, pharmacological properties and side effects of VKAs, which are used in the management of cardiovascular diseases, including coronary heart disease (where their use is limited), stroke prevention in atrial fibrillation, heart valves and/or chronic heart failure. Using an evidence-based approach, we describe the results of completed clinical trials, highlight areas of uncertainty, and recommend therapeutic options for specific disorders. Although VKAs are being increasingly replaced in most patients with non-valvular atrial fibrillation by the new oral anticoagulants, which target either thrombin or FXa, the VKAs remain the agents of choice for patients with atrial fibrillation in the setting of rheumatic valvular disease and for those with mechanical heart valves.