How to manage warfarin therapy

Risk Factors Associated With Exclusion of Obese Patients Ischemic Stroke With a History of Smoking From Thrombolysis Therapy

The objective of this study is to determine risk factors that may contribute to exclusion decision from recombinant tissue plasminogen activator (rtPA) in patients with acute ischemic stroke (AIS) with a combined current or history of smoking and obesity. This study was conducted on data from 5469 patients with AIS collected from a regional stroke registry. Risk factors associated with inclusion or exclusion from rtPA were determined using multivariate logistic regression analysis. The adjusted odds ratios and 95% confidence interval for each risk factor were used to predict the increasing odds of an association of a specific risk factor with exclusion from rtPA. In the adjusted analysis, obese patients with AIS with a history of smoking (current and previous) excluded from rtPA were more likely to present with carotid artery stenosis (OR = 0.069, 95% CI 0.011-0.442), diabetes (OR = 0.604, 95% CI 0.366-0.997), higher total cholesterol (OR = 0.975, 95% CI 0.956-0.995), and history of alcohol use (OR = 0.438, 95% CI 0.232-0.828). Higher NIHSS score (OR = 1.051, 95% CI 1.017-1.086), higher triglycerides (OR = 1.004, 95% CI 1.001-1.006), and higher high-density lipoprotein (OR = 1.028, 95% CI 1.000-1.057) were associated with the inclusion for rtPA. Our findings reveal specific risk factors that contribute to the exclusion of patients with AIS with a combined effect of smoking and obesity from rtPA. These findings suggest the need to develop management strategies to improve the use of rtPA for obese patients with AIS with a history of smoking.

An Adaptive Model Predictive Controller to Address the Biovariability in Blood Clotting Response During Therapy With Warfarin

OBJECTIVE

Effective dosing of anticoagulants aims to prevent blood clot formation while avoiding hemorrhages. This complex task is challenged by several disturbing factors and drug-effect uncertainties, requesting frequent monitoring and adjustment. Biovariability in drug absorption and action further complicates titration and calls for individualized strategies. In this paper, we propose an adaptive closed-loop control algorithm to assist in warfarin therapy management.

METHODS

The controller was designed and tested in silico using an established pharmacometrics model of warfarin, which accounts for inter-subject variability. The control algorithm is an adaptive Model Predictive Control (a-MPC) that leverages a simplified patient model, whose parameters are updated with a Bayesian strategy. Performance was quantitatively evaluated in simulations performed on a population of virtual subjects against an algorithm reproducing medical guidelines (MG) and an MPC controller available in the literature (l-MPC).

RESULTS

The proposed a-MPC significantly (p 0.05) lowers rising time (2.8 vs. 4.4 and 11.2 days) and time out of range (3.3 vs. 7.2 and 12.9 days) with respect to both MG and l-MPC, respectively. Adaptivity grants a significantly (p 0.05) lower number of subjects reaching unsafe INR values compared to when this feature is not present (8.9% vs.15% of subjects presenting an overshoot outside the target range and 0.08% vs. 0.28% of subjects reaching dangerous INR values).

CONCLUSION

The a-MPC algorithm improve warfarin therapy compared to the benchmark therapies.

SIGNIFICANCE

This in-silico validation proves effectiveness of the a-MPC algorithm for anticoagulant administration, paving the way for clinical testing.

Warfarin pharmacogenetics in a black Zimbabwean cohort: an observational prospective study

Aim: A prospective observational study was conducted to evaluate the feasibility of implementing clinical guidelines for warfarin dosing in black Zimbabwean patients. Methods: CYP2C9*5, CYP2C9*6, CYP2C9*8 and CYP2C9*11 and VKORC1 c. 1639 G>A variations were observed in 62 study patients. Results & Conclusion: Overall, 39/62 (62.90%) participants did not receive a warfarin starting dose as would have been recommended by Clinical Pharmacogenetics Implementation Consortium guidelines. US FDA and Dutch Pharmacogenetics Working Group guidelines are based on CYP2C9*2 and CYP2C9*3 only, hence, unlikely useful in this cohort, where such variants were not detected. Clinical Pharmacogenetics Implementation Consortium guidelines, on the other hand, have a specific recommendation on the African-specific variants CYP2C9*5, CYP2C9*6 and CYP2C9*11, and are hence suitable for implementation in Zimbabwe and would help optimize warfarin doses in patients in the study cohort.

Automated warfarin dose prediction for Asian, American, and Caucasian populations using a deep neural network

Existing warfarin dose prediction algorithms based on pharmacogenetics and clinical parameters have not been used clinically due to the absence of external validation, lack of assessment for clinical utility, and high risk of bias. Moreover, given the high degree of heterogeneity across different datasets used to develop these algorithms, it is unsurprising that prediction errors remain high, and dosing accuracy is dependent on specific ethnic populations. To circumvent these challenges, deep neural models are increasingly used to improve the precision and accuracy of warfarin dose predictions. Hence, this study sought to develop a deep learning-based model using a well-established curated dataset of over 6000 patients from the International Warfarin Pharmacogenomics Consortium (IWPC). Clinically-relevant input data such as physical attributes, medical conditions, concomitant medications, genotype status of functional warfarin genetic polymorphisms, and therapeutic INR were entered followed by applying a unique and robust training and validation method. The deep model yielded a low average mean absolute error (MAE) of 7.6 mg/week and a relatively low mean percentage of error of 40.9% in Asians, 14.2 mg/week MAE and 36.9% in African Americans, and 12.7 mg/week MAE and 45.4% mean percentage of error in White Caucasians. This model also resulted in 36.4% of all patients with a predicted dose within 20% of the administered dose. Hence, our proposed deep model provides an alternative to predicting warfarin dose in the clinical setting upon validation in ethnically-similar datasets.

Standard-Intensity Versus Low-Intensity Anticoagulation with Warfarin in Asian Patients with Atrial Fibrillation: A Multi-Center, Randomized Controlled Trial

Anticoagulation with warfarin in Asian patients with atrial fibrillation (AF) often has been decreased as an international normalized ratio (INR) of prothrombin time 1.6-2.6 due to fear of bleeding, although universal criteria recommend an INR of 2.0-3.0. In this randomized, open-label trial, low-intensity anticoagulation (INR 1.6-2.6) was compared with standard-intensity anticoagulation (INR 2.0-3.0) with warfarin. A total 616 patients with AF and at least 1 risk factor for stroke were randomized to low-intensity anticoagulation (n = 308) and standard-intensity anticoagulation (n = 308) groups. The intention-to-treat analysis was performed to determine differences. The baseline characteristics of the two groups were comparable. New-onset stroke occurred in 2 patients (0.44% per year) in the low-intensity group and 5 patients (1.05% per year) in the standard-intensity group (HR 0.42, 95% CI 0.08-2.15). Major bleeding occurred in 4 patients (0.89% per year) in the low-intensity group and 5 patients (1.06% per year) in the standard-intensity group (HR 0.84, 95% CI 0.22-3.11). The rate of the net clinical outcome (composite of stroke, systemic embolism, major bleeding, and death) was 1.33% per year in the low-intensity group compared with 2.12% per year in the standard-intensity group (HR 0.63, 95% CI 0.23-1.72). In Asian patients with AF, clinical outcomes were not different between low-intensity and standard-intensity anticoagulation with warfarin.

Fibrinogen, Coagulation, and Ageing

The World Health Organization estimates that the world's population over 60 years of age will nearly double in the next 30 years. This change imposes increasing demands on health and social services with increased disease burden in older people, hereafter defined as people aged 60 years or more. An older population will have a greater incidence of cardiovascular disease partly due to higher levels of blood fibrinogen, increased levels of some coagulation factors, and increased platelet activity. These factors lead to a hypercoagulable state which can alter haemostasis, causing an imbalance in appropriate coagulation, which plays a crucial role in the development of cardiovascular diseases. These changes in haemostasis are not only affected by age but also by gender and the effects of hormones, or lack thereof in menopause for older females, ethnicity, other comorbidities, medication interactions, and overall health as we age. Another confounding factor is how we measure fibrinogen and coagulation through laboratory and point-of-care testing and how our decision-making on disease and treatment (including anticoagulation) is managed. It is known throughout life that in normal healthy individuals the levels of fibrinogen and coagulation factors change, however, reference intervals to guide diagnosis and management are based on only two life stages, paediatric, and adult ranges. There are no specific diagnostic guidelines based on reference intervals for an older population. How ageing relates to alterations in haemostasis and the impact of the disease will be discussed in this chapter. Along with the effect of anticoagulation, laboratory testing of fibrinogen and coagulation, future directions, and implications will be presented.

Comparison of real-world clinical and economic outcomes in patients receiving oral anticoagulants: A retrospective claims analysis

BACKGROUND: Direct oral anticoagulants (DOACs) have become widely used for the prevention of stroke in nonvalvular atrial fibrillation (AF) and for the treatment of venous thromboembolism (VTE). Warfarin, the standard of care prior to DOACs, requires monitoring and dose adjustment to ensure patients remain appropriately anticoagulated. DOACs do not require monitoring but are significantly more expensive. We sought to examine real-world effectiveness and costs of DOACs and warfarin in patients with AF and VTE. OBJECTIVE: To examine clinical and economic outcomes. The clinical objectives were to determine the bleeding and thrombotic event rates associated with DOACs vs warfarin. The economic objectives were to determine the cost associated with these events, as well as the all-cause medical and pharmacy costs associated with DOACs vs warfarin. METHODS: This analysis was an observational, propensity-matched comparison of retrospective medical and pharmacy claims data for members enrolled in an integrated health plan between October 1, 2015, and September 30, 2020. Members who were older than 18 years of age with at least 1 30-day supply of warfarin or a DOAC filled within 30 days of a new diagnosis of VTE or nonvalvular AF were eligible for the analysis. Cox hazard ratios were used to compare differences in clinical outcomes, where paired t-tests were used to evaluate economic outcomes. RESULTS: After matching, there were 893 patients in each group. Among matched members, warfarin was associated with increased risk of nonmajor bleeds relative to apixaban (hazard ratio [HR] = 1.526; P = 0.0048) and increased risk of pulmonary embolism relative to both DOACs (apixaban: HR = 1.941 [P = 0.0328]; rivaroxaban: HR = 1.833 [P = 0.0489]). No statistically significant difference was observed in hospitalizations or in length of stay between warfarin and either DOAC. The difference-in-difference (DID) in total costs of care per member per month for apixaban and rivaroxaban relative to warfarin were $801.64 (P = 0.0178) and $534.23 (P = 0.0998) more, respectively. DID in VTE-related cost for apixaban was $177.09 less, relative to warfarin (P = 0.0098). DID in all-cause pharmacy costs for apixaban and rivaroxaban relative to warfarin were $342.47 (P < 0.0001) and $386.42 (P < 0.001) more, respectively. CONCLUSIONS: Warfarin use was associated with a significant decrease in total cost of care despite a significant increase in VTE-related costs vs apixaban. Warfarin was also associated with a significant increase in other nonmajor bleeds relative to apixaban, as well as a significant increase in pulmonary embolism relative to both DOACs. Warfarin was associated with a significant reduction in all-cause pharmacy cost compared with either DOAC. DISCLOSURES: The authors of this study have nothing to disclose.

Long Short-Term Memory Network for Development and Simulation of Warfarin Dosing Model Based on Time Series Anticoagulant Data

Background

Warfarin is an effective treatment for thromboembolic disease but has a narrow therapeutic index, and dosage can differ tremendously among individuals. The study aimed to develop an individualized international normalized ratio (INR) model based on time series anticoagulant data and simulate individualized warfarin dosing.

Methods

We used a long short-term memory (LSTM) network to develop an individualized INR model based on data from 4,578 follow-up visits, including clinical and genetic factors from 624 patients whom we enrolled in our previous randomized controlled trial. The data of 158 patients who underwent valvular surgery and were included in a prospective registry study were used for external validation in the real world.

Results

The prediction accuracy of LSTM_INR was 70.0%, which was much higher than that of MAPB_INR (maximum posterior Bayesian, 53.9%). Temporal variables were significant for LSTM_INR performance (51.7 vs. 70.0%, P < 0.05). Genetic factors played an important role in predicting INR at the onset of therapy, while after 15 days of treatment, we found that it might unnecessary to detect genotypes for warfarin dosing. Using LSTM_INR, we successfully simulated individualized warfarin dosing and developed an application (AI-WAR) for individualized warfarin therapy.

Conclusion

The results indicate that temporal variables are necessary to be considered in warfarin therapy, except for clinical factors and genetic factors. LSTM network may have great potential for long-term drug individualized therapy.

Trial Registration

NCT02211326; www.chictr.org.cn:ChiCTR2100052089.

Development of an interview-based warfarin nomogram predicting the time spent in the therapeutic INR range: a cost-effective, and non-invasive strategy building from a cross sectional study in a low resource setting

A cross-sectional study was conducted to predict time in therapeutic range (TTR) using clinical history, examination, and socioeconomic data. Study included warfarin-receiving patients from outpatient-clinic. In 203 patients studied, mean warfarin start-dose was 2.55 mg/day and maintenance-dose/week was 30.79 mg. Body mass index (BMI) (p = 0.03), warfarin maintenance dose/day (p = 0.02), and comorbidity presence (p = 0.04) were significantly associated with TTR. Occupation (p = 0.53), income (p = 0.83), education (p = 0.55), and socioeconomic score (p = 0.73) showed non-significant association with TTR. A TTR predicting nomogram was built from clinical history and examination findings.

Point-of-Care Device for Assessment of Blood Coagulation Status in COVID-19 Patients

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent driving the current COVID-19 pandemic. The acute respiratory distress that occurs in some severe COVID-19 cases has been linked with hypercoagulation or thrombotic events as well as a worse prognosis and increased risk of death. Thus, point-of-care devices that can be used for early detection of coagulation abnormalities would assist in COVID-19 management. This chapter describes the use of the Roche Diagnostics CoaguChek^® XS test kit for potential use in COVID-19 personalized medicine approaches.

Does Ramadan fasting disrupt international normalised ratio control in warfarin-treated medically stable patients?

AIM

Warfarin is commonly used in patients with thrombotic diseases. This study aimed to evaluate the impact of Ramadan fasting on warfarin efficacy by investigating international normalised ratio (INR) stability in medically stable patients.

METHODS

A retrospective observational study was conducted at King Khalid University Hospital during Ramadan 2016 on fasting adult patients aged above 18 years and receiving warfarin. The INR values during pre-Ramadan, Ramadan and post-Ramadan periods were collected after satisfying the inclusion criteria. Time within the therapeutic range (TTR) during the whole period was estimated using the conventional method.

RESULTS

In total, 101 patients were included in the study. The mean age (SD) was 55.8 ± 15.5 years, and 52.4% were females. The target INR range for 62.4% was 2-3, while 37.6% had a target INR range of 2.5-3.5. An upward trend in the proportion of patients with therapeutic INR was noticed during Ramadan (59.4%) as compared to pre- (56.4%) and post-Ramadan periods (53.5%) respectively. Additionally, the proportions of patients with supratherapeutic and sub-therapeutic INR were the highest and lowest, 23% and 24% respectively post-Ramadan as compared to other periods. Based on target INR categorisation, achieving therapeutic INR during Ramadan was more feasible with the low INR (2-3) compared to the high INR (2.5-3.5) target patients, 63.5% vs 52.6% respectively. TTR estimation revealed 62.4% and 37.6% of the patients had good and poor, respectively, anticoagulation status throughout the study period.

CONCLUSION

Despite the changes in mean INR and proportion of patients with therapeutic INR during Ramadan compared to other non-fasting months, our results confirmed that short-term fasting during Ramadan has no significant influence on INR stability and, consequently, therapeutic efficacy in warfarin-treated medically stable patients.

Drugs in phase I and II clinical development for the prevention of stroke in patients with atrial fibrillation

INTRODUCTION

Atrial fibrillation is the most frequently diagnosed cardiac arrhythmia globally and is associated with ischemic stroke and heart failure. Patients with atrial fibrillation are typically prescribed long-term anticoagulants in the form of either vitamin K antagonists or non-vitamin K antagonist oral anticoagulants; however, both carry a potential risk of adverse bleeding.

AREAS COVERED

This paper sheds light on emerging anticoagulant agents which target clotting factors XI and XII, or their activated forms - XIa and XIIa, respectively, within the intrinsic coagulation pathway. The authors examined data available on PubMed, Scopus, and the clinical trials registry of the United States National Library of Medicine (www.clinicaltrials.gov).

EXPERT OPINION

Therapies targeting factors XI or XII can yield anticoagulant efficacy with the potential to reduce adverse bleeding. Advantages for targeting factor XI or XII include a wider therapeutic window and reduced bleeding. Long-term follow-up studies and a greater understanding of the safety and efficacy are required. Atrial fibrillation is a chronic disease and therefore the development of oral formulations is key.

Impact of pharmacists' training on oral anticoagulant counseling: A randomized controlled trial

OBJECTIVE

The study evaluated the impact of oral anticoagulant counseling training on the quality of counseling provided by pharmacists.

METHODS

A prospective RCT was conducted among 33 pharmacists from 23 pharmacies in Ibadan, Nigeria. Six mystery patients (MPs) who were either warfarin-naïve, experienced adverse drug reaction (ADR), or drug interaction (DI) to warfarin were used to assess pharmacists' oral anticoagulant counseling quality at pre- and post-intervention. A 2-week online oral anticoagulant counseling training was given to the intervention group pharmacists. Quality of counseling was categorized as poor (0-20 %), fair (21-50 %), moderate (51-80 %), and optimal (81-100 %).

RESULTS

At pre-intervention, the quality of oral anticoagulant counseling provided to the MPs was poor. Post-intervention, the quality improved among pharmacists in the intervention group, from poor to fair for both warfarin-naïve MP and MP who experienced DI, and from fair to moderate for MP with ADR.

CONCLUSION

Short-term online oral anticoagulant counseling training improved the quality of counseling provided by community pharmacists to mystery patients on warfarin.

PRACTICE IMPLICATION

Online oral anticoagulant counseling training may be employed by pharmacists' professional bodies intermittently to improve oral anticoagulant counseling.

Reweighting Oranges to Apples: Transported RE-LY Trial Versus Nonexperimental Effect Estimates of Anticoagulation in Atrial Fibrillation

BACKGROUND

Results from trials and nonexperimental studies are often directly compared, with little attention paid to differences between study populations. When target and trial population data are available, accounting for these differences through transporting trial results to target populations of interest provides useful perspective. We aimed to compare two-year risk differences (RDs) for ischemic stroke, mortality, and gastrointestinal bleeding in older adults with atrial fibrillation initiating dabigatran and warfarin when using trial transport methods versus nonexperimental methods.

METHODS

We identified Medicare beneficiaries who initiated warfarin or dabigatran from a 20% nationwide sample. To transport treatment effects observed in the randomized evaluation of long-term anticoagulation trial, we applied inverse odds weights to standardize estimates to two Medicare target populations of interest, initiators of: (1) dabigatran and (2) warfarin. Separately, we conducted a nonexperimental study in the Medicare populations using standardized morbidity ratio weighting to control measured confounding.

RESULTS

Comparing dabigatran to warfarin, estimated two-year RDs for ischemic stroke were similar with trial transport and nonexperimental methods. However, two-year mortality RDs were closer to the null when using trial transport versus nonexperimental methods for the dabigatran target population (transported RD: -0.57%; nonexperimental RD: -1.9%). Estimated gastrointestinal bleeding RDs from trial transport (dabigatran initiator RD: 1.8%; warfarin initiator RD: 1.9%) appeared more harmful than nonexperimental results (dabigatran initiator RD: 0.14%; warfarin initiator RD: 0.57%).

CONCLUSIONS

Differences in study populations can and should be considered quantitatively to ensure results are relevant to populations of interest, particularly when comparing trial with nonexperimental findings. See video abstract: http://links.lww.com/EDE/B703.

Real-world on-treatment and initial treatment absolute risk differences for dabigatran vs warfarin in older US adults

PURPOSE

Trials and past observational work compared dabigatran and warfarin in patients with atrial fibrillation, but few reported estimates of absolute harm and benefit under real-world adherence patterns, particularly in older adults that may have differing benefit-harm profiles. We aimed to estimate risk differences for ischemic stroke, death, and gastrointestinal bleeding after initiating dabigatran and warfarin in older adults (a) when patients adhere to treatment and (b) under real-world adherence patterns.

METHODS

In a 20% sample of nationwide Medicare claims from 2010 to 2015, we identified beneficiaries aged 66 years and older initiating warfarin and dabigatran. We followed individuals from initiation until death or October 2015 (initial treatment, IT) and separately censored individuals' follow-up after drug switches and gaps in supply (on-treatment, OT). We applied inverse probability of treatment and standardized morbidity ratio weights, as well as inverse probability of censoring weights, to estimate two-year risk differences (RDs) for dabigatran vs warfarin.

RESULTS

We identified 10,717 dabigatran and 74,891 warfarin initiators. Weighted OT RDs suggested decreased ischemic stroke risk for dabigatran vs warfarin; IT RDs indicated increased or no change in ischemic stroke risk. Regardless of follow-up approach and weighting strategy, risk of death appeared lower and risk of gastrointestinal bleeding appeared higher when comparing dabigatran vs warfarin.

CONCLUSIONS

Dabigatran use was associated with lower risks of mortality and ischemic stroke in routine care when older adults stayed on treatment. IT analyses suggested that these benefits may be diminished under real-world patterns of switching and discontinuation.

Technology-Based Interventions in Oral Anticoagulation Management: Meta-Analysis of Randomized Controlled Trials

Background

An increasing number of patients have received prophylactic or therapeutic oral anticoagulants (OACs) for thromboembolic complications of diseases. The use of OACs is associated with both clinical benefits and risks. Considering the challenges imposed by this class of drugs, as well as the enormous progress made in portable device technology, it is possible that technology-based interventions may improve clinical benefits for patients and optimize anticoagulation management.

Objective

This study was designed to comprehensively evaluate the role of technology-based interventions in the management of OACs.

Methods

We searched 6 databases—PubMed, EMBASE, Cochrane, Cumulative Index to Nursing and Allied Health Literature, Scopus, and PsycINFO—to retrieve relevant studies published as of November 1, 2019, to evaluate the effect of technology-based interventions on oral anticoagulation management. RevMan (version 5.3; Cochrane) software was used to evaluate and analyze clinical outcomes. The methodological quality of studies was assessed by the Cochrane risk of bias tool.

Results

A total of 15 randomized controlled trials (RCTs) were selected for analysis. They reported data for 2218 patients (1110 patients in the intervention groups and 1108 patients in the control groups). A meta-analysis was performed on the effectiveness and safety data reported in the RCTs. Technology-based interventions significantly improved the effectiveness of oral anticoagulation management (mean difference [MD]=6.07; 95% CI 0.84-11.30; I²=72%; P=.02). The safety of oral anticoagulation management was also improved, but the results were not statistically significant. Bleeding events were reduced (major bleeding events MD=1.02; 95% CI 0.78-1.32; I²=0%; P=.90; minor bleeding events MD=1.06, 95% CI 0.77-1.44; I²=41%; P=.73) and thromboembolism events were reduced (MD=0.71; 95% CI 0.49-1.01; I²=0%; P=.06). In general, patients were more satisfied with technology-based interventions, which could also improve their knowledge of anticoagulation management, improve their quality of life, and reduce mortality and hospitalization events.

Conclusions

Using technology to manage OACs can improve the effectiveness and safety of oral anticoagulation management, result in higher patient satisfaction, and allow greater understanding of anticoagulation.

Comparing Two Methods of Tablet Manipulation to Adjust the Warfarin Dose in Paediatric Care

Tablets containing prescribed doses are not always available, and this is of particular importance in paediatric care where suitable age-appropriate formulations are generally lacking. To obtain a child-adjusted dose, tablets are manipulated in several ways; e.g., they may be dispersed in water before a fraction is extracted, or they may be split before the resulting fragment is dispersed. In this study, the accuracy attained through these manipulation methods was investigated for two generic tablets containing the anticoagulant warfarin. Tablets were dispersed in water (10 mL) before a fraction (10%) was withdrawn, alternatively tablets were split in half or quarter fragments before the fragments were dispersed in water. To investigate the contribution of variability from the different steps in the manipulation processes, the amount of warfarin recovered from the various dispersions was determined, as was the accuracy of the splitting. A validated UHPLC-method was used for quantitative determination of warfarin. Splitting of the tablets could result in deviation >30% from the ideal, theoretical weight. The amount of drug substance extracted as a fraction from the dispersed tablets deviated no more than 10% from the intended amount. To obtain the most accurate child-adjusted fraction dose of warfarin, the tablets investigated in this study should be dispersed and the desired proportion extracted. Practices that involve splitting tablets are likely to increase the variation, and should be avoided.

Effect of Quinolones Versus Cefixime on International Normalized Ratio Levels After Valve Replacement Surgery with Warfarin Therapy

Background and Objectives: A dispute over interaction of warfarin with two quinolones—i.e., moxifloxacin and levofloxacin—leading to significant increase in international normalized ratio (INR) levels and coagulopathies is currently in debate. The study objective was to compare the INR values due to addition of quinolones and cefixime in warfarin treated patients after replacement of disease valves with metallic valves. Material and Methods: A prospective evaluation of patients who undergone valve replacement surgeries in the cardiology hospital setup in Pakistan during the period 2018–2019 was done, including all those subjects treated concurrently with levofloxacin, moxifloxacin, cefixime, and warfarin for the study. Data organized included demographic information, concurrent medications, and appropriate analytical parameters, especially INR values taken before and within seven days after prescribing three antibiotics in discharged patients who had undergone valve replacement surgeries. Patients for whom laboratory INR values were not given at the time of discharge and with deranged liver function, renal function, low albumin levels, and febrile patients were removed from study. Furthermore, patients were advised on possible food interactions and evaluated to examine if these factors have any possible influence on the interaction being studied. Results: Differences in INR were analyzed statistically by means of SPSS analysis before and after the possible interaction. Following the administration of levofloxacin and moxifloxacin to warfarin therapy, statistical analysis showed remarkable increase in INR (p < 0.001) and no significant change in INR was observed after cefixime treatment (p > 0.05). Conclusion: Results showed that, after adding levofloxacin and moxifloxacin in patients on warfarin, therapy contributed to remarkable increase in INR. However, addition of cefixime prevented frequent coagulopathies; therefore, close monitoring of INR and switching to a safe antibiotic such as cefixime is recommended.

Patient Feedback on a Warfarin Action Plan Used in a Local Australian Physician Practice Setting

BACKGROUND

Warfarin is a high-risk medicine, and older persons (those aged 65 years and older)1,2 who take this therapy need medicines information about it that is at a level which is both understandable and comprehensive to improve their knowledge about the risks and benefits of warfarin therapy.3,4 Therefore, the primary objective of this study was to report patient feedback on a Warfarin Action Plan (WAP) (leaflet) and identify patients' preferences regarding its content and format. The secondary objective was to canvass in-depth feedback regarding the participants' information needs and current information-seeking practices with respect to warfarin therapy.

METHOD

In an Australian General Practice medical centre setting, a qualitative study comprising 34 individual interviews was conducted. Emergent themes were elicited via a qualitative analysis using manual inductive coding.

RESULTS

The majority of participants gave very positive feedback on the WAP leaflet, stating that it was a useful and concise resource. In canvasing this feedback, 4 themes emerged: (1) the need for information about warfarin therapy, (2) reliance on doctors and/or pharmacists for information, (3) the need for information to normalize their daily life, and (4) patients and carers acting on the new information.

CONCLUSION

The WAP is a simple and well-received tool that meets the knowledge and education needs about warfarin therapy for older people and their carers.

Pharmacogenetics of Warfarin in a Diverse Patient Population

INTRODUCTION

Many warfarin-related genotypes have shown to impact the average daily warfarin (ADW) dose requirements; however, information in non-Caucasian populations is limited.

OBJECTIVES

To identify the frequencies of 4 warfarin-related gene polymorphisms in an ethnically diverse patient population and to examine their impact with other clinical variables on ADW dose requirements.

METHODS

Patients were recruited from 2 anticoagulation clinics in the Los Angeles area. Blood samples were collected and genotyped for vitamin K epoxide reductase (VKORC1), CYP2C9*2, CYP2C9*3, and CYP4F2 after informed consent. Charts were reviewed to collect demographic, clinical, and warfarin dosing data.

RESULTS

A total of 291 patients were included (120 Caucasians, 127 Hispanics, and 44 Asians). In patients with wild-type genotypes for VKORC1, CYP2C9*2, CYP2C9*3, and CYP4F2, the highest warfarin requirement was found in Caucasians, lower in Hispanics, and lowest in Asians. Homozygous VKORC1 variant carriers were detected in 15%, 15%, and 79% in Caucasians, Hispanics, and Asians, respectively. Progressive lowering of ADW doses were associated with each VKORC1 variant in Caucasians and Hispanics, but the results in wild-type/ heterozygote Asians were unclear. CYP2C9 variants were associated with lower ADW doses; frequencies of CYP2C9*2 and CYP2C9*3 mutations were higher in Caucasians than in Hispanics but rare to none in Asians. The frequencies of CYP4F2 variant were similar across all ethnicities, but their impact on warfarin dose requirement were insignificant. Clinical factors such as age, body surface area, history of coronary artery disease, deep vein thrombosis or atrial fibrillation, and concomitant amiodarone or HMG-CoA reductase inhibitors had varying impact on the ADW requirements in the ethnicities studied.

CONCLUSIONS

Our study demonstrated differences among 3 ethnic groups in terms of ADW dose requirements and the impact of associated clinical variables. The results suggest that a single model for all ethnicities may not provide the best performance in predicting warfarin dose requirements.

Characteristics of software used in self-management of vitamin K antagonist therapy: A systematic review

INTRODUCTION AND GOAL

Currently, 1-2% of the population in developed countries are under treatment with oral anticoagulants. An appropriate strategy to deal with this increase in demand of treatment with oral anticoagulants and to manage the costs is the transfer of part or all of the responsibility for managing treatment to the patients. The use of information technology, particularly electronic health software, can be an appropriate method to improve the quality of self-management of treatment with these drugs. Therefore, this systematic review investigated studies that discuss the characteristics of electronic health software in self-management of oral anticoagulation therapy.

METHOD

A systematic review based on PRISMA protocol was conducted. In this study, articles were investigated that were in English. Articles existing in Cochrane, EMBASE and PubMed databases were searched up to 14 May 2017. Then, articles searched through Google Scholar were added to this study.

FINDINGS

The common characteristics used in most software included 'encryption in exchanging information', having an 'instruction module' and 'being Android-based'. In terms of functionality, 'communication between the patient and healthcare team' existed in most of the software.

CONCLUSION

The results of the study showed that the accuracy of administration of the dose of the drug using computer to reach a target international normalized ratio level was not less than those administered with experienced medical staff. In addition, the results indicated that important characteristics of the software include encryption in exchanging information, instruction module and Android-based instruction module. The most important characteristic was the interaction between the patient and the healthcare team.

Association between polymorphisms of VKORC1 and CYP2C9 genes with warfarin maintenance dose in a group of warfarin users in Birjand city, Iran

Warfarin is the cardinal anticoagulant drug prescribed around the world. Due to stochastic bleeding in patients, it is essential to adjust the dose for every individual. The aim of the present study was to evaluate the frequency of CYP2C9 and VKORC1 gene polymorphisms and their association with warfarin maintenance dose in a sample of cardiovascular patients in Birjand, South-Khorasan province of Iran. Patients with a history of cardiovascular disorders who take warfarin daily were selected. CYP2C9 and VKORC1 gene polymorphisms were detected by polymerase chain reaction-restriction fragment length polymorphism in all participants. A total of 114 patients (mean age: 52.7 ± 14.9 years, M/F ratio: 0.76) participated in this study. Regarding CYP2C9 gene polymorphisms, the most frequent genotype was 1*/1* (80.4% in females and 62.5% in males). The frequency of 1*/2* and 2*/2* variants was 13% and 6.5% in females and 25% and 12.5% in males, respectively. The frequency of VKORC1 gene (1639 G > A), was 31.5%, 39.5%, and 29% for GG, GA, and AA in males, respectively. Besides, the mentioned genotype frequencies for females were 50%, 40.5%, and 9.5%, respectively. Moreover, there was a statistically significant correlation between VKORC1 gene -1639 G > A variant and warfarin maintenance dose (P < 0.001) but not for CYP2C9 variants. The results of the current study confirmed that the mutant variants of CYP2C9 are not frequent and do not have any impact on warfarin dose. In the case of VKORC1, the mutant allele (A) showed a positive correlation with warfarin dose adjustment.

Compliance with pathology testing guidelines in Australian general practice: protocol for a secondary analysis of electronic health record data

INTRODUCTION

In Australia, general practitioners usually are the first point of contact for patients with non-urgent medical conditions. Appropriate and efficient utilisation of pathology tests by general practitioners forms a key part of diagnosis and monitoring. However overutilisationand underutilisation of pathology tests have been reported across several tests and conditions, despite evidence-based guidelines outlining best practice in pathology testing. There are a limited number of studies evaluating the impact of these guidelines on pathology testing in general practice. The aim of our quantitative observational study is to define how pathology tests are used in general practice and investigate how test ordering practices align with evidence-based pathology guidelines.

METHODS AND ANALYSIS

Access to non-identifiable patient data will be obtained through electronic health records from general practices across three primary health networks in Victoria, Australia. Numbers and characteristics of patients, general practices, encounters, pathology tests and problems managed over time will be described. Overall rates of encounters and tests, alongside more detailed investigation between subcategories (encounter year, patient's age, gender, and location and general practice size), will also be undertaken. To evaluate how general practitioner test ordering coincides with evidence-based guidelines, five key candidate indicators will be investigated: full blood counts for patients on clozapine medication; international normalised ratio measurements for patients on warfarin medication; glycated haemoglobin testing for monitoring patients with diabetes; vitamin D testing; and thyroid function testing.

ETHICS AND DISSEMINATION

Ethics clearance to collect data from general practice facilities has been obtained by the data provider from the RACGP National Research and Evaluation Ethics Committee (NREEC 17-008). Approval for the research group to use these data has been obtained from Macquarie University (5201700872). This study is funded by the Australian Government Department of Health Quality Use of Pathology Program (Agreement ID: 4-2QFVW4M). Findings will be reported to the Department of Health and disseminated in peer-reviewed academic journals and presentations (national and international conferences, industry forums).

Retrospective cohort study for evaluating the INR monitoring patterns in patients with deep vein thrombosis in daily practice: Analysis of 2010-2013 database of a tertiary care center

OBJECTIVE

To evaluate the international normalized ratio (INR) monitoring patterns in patients with deep vein thrombosis.

METHODS

Of 32,012 patients with ≥1 outpatient INR measurement and 42,582 patients with confirmed deep vein thrombosis diagnosis registered to our hospital between 1 January 2010 and 31 December 2013, 6720 records were identified to have both deep vein thrombosis and international normalized ratio measurement, and 4.377 out of 6.720 single patient records were determined to be statistically analyzable.

RESULTS

Median INR measurement frequency was 6.47 times/year and patients had INR levels of 2-3 in 34.3% of follow-up time. Having ≥70% vs. <70% of follow-up time within therapeutic range was associated with lower hospital admission frequency (9.7 vs. 10.3 times/year).

CONCLUSION

Our study revealed only one-third of the follow-up time to be spent within therapeutic INR, association of INR therapeutic range with lesser number of hospital admissions and INR monitoring frequency of 6.47 times/year despite lack of stable INR control in most of the deep vein thrombosis patients.

Dedicated warfarin care programme results in superior warfarin control in Queensland, Australia

BACKGROUND

Warfarin is used to prevent stroke in patients with atrial fibrillation (AF). Ongoing monitoring of International normalised ratio (INR) and time in therapeutic range (TTR) commonly used to assess the quality of warfarin management are required. Anticoagulant clinics have demonstrated improved TTRs, particularly in countries with poorer control in primary care settings. Reported TTR in Australia has been relatively high; so, it is unknown if benefit would be seen from dedicated warfarin clinics in Australia. The aim of this study was to compare the level of warfarin control in patients managed by their general practitioner (GP) and a warfarin care programme (WCP) by Sullivan Nicolaides Pathology.

METHOD

Retrospective data were collected for AF patients enrolled in the warfarin care programme at WCP, and included patients with INR tests available while managed by their GP. INR tests were used to calculate TTR and frequency of testing for the time managed by GP and WCP, with mean data used for analysis and comparison.

RESULTS

The eligible 200 warfarin patients had a TTR of 69% with GP management and 82% with WCP management (<.0001). Significant differences were also found between GP and WCP management in the percentage of tests in range, total number of tests and frequency of testing. WCP had a reduced time to repeat test at extremes of INR results.

CONCLUSION

Australian warfarin control was good when managed by either GP or WCP, but WCP management increased TTR by 13%. Dedicated warfarin programmes can improve warfarin control and optimise therapy for patients.

Health literacy and knowledge in a cohort of Australian patients taking warfarin

OBJECTIVES

To 1) characterise older patients taking warfarin, 2) assess these patients' level of warfarin knowledge, and 3) describe their strengths and limitations in health literacy, and 4) explore relationships between participants' characteristics, warfarin knowledge and health literacy.

METHODS

A warfarin knowledge questionnaire and Health Literacy Questionnaire (HLQ) were administered to older patients (aged >65 years, N=34) taking warfarin in an Australian general practice setting.

RESULTS

Key gaps in participant knowledge pertained to the consequences of an international normalized ratio (INR) being below the target INR range and safety issues such as when to seek medical attention. A limitation for participants with a lower level of health literacy was the ability to appraise health information. Patients who needed assistance in completing the HLQs had significantly lower warfarin knowledge scores (p=0.03). Overseas-born participants and those taking 5 or more long-term medications had lower HLQ scores for specific scales (p<0.05).

CONCLUSION

In this study warfarin knowledge gaps and a limitation of health literacy amongst a small sample of older patients were identified. The findings suggest that education and resources may need to be tailored to the needs of older patients taking warfarin and their carers to address these knowledge gaps and limitations in health literacy. Patients who may need greater support include those that need assistance in completing the HLQ, are overseas-born, or are taking 5 or more long-term medications.

Interaction of quercetin and its metabolites with warfarin: Displacement of warfarin from serum albumin and inhibition of CYP2C9 enzyme

Flavonoids are ubiquitous molecules in nature with manifold pharmacological effects. Flavonoids interact with several proteins, and thus potentially interfere with the pharmacokinetics of various drugs. Though much is known about the protein binding characteristics of flavonoid aglycones, the behaviour of their metabolites, which are extensively formed in the human body has received little attention. In this study, the interactions of the flavonoid aglycone quercetin and its main metabolites with the albumin binding of the oral anticoagulant warfarin were investigated by fluorescence spectroscopy and ultrafiltration. Furthermore, the inhibitory effects of these flavonoids on CYP2C9 enzyme were tested because the metabolic elimination of warfarin is catalysed principally by this enzyme. Herein, we demonstrate that each tested flavonoid metabolite can bind to human serum albumin (HSA) with high affinity, some with similar or even higher affinity than quercetin itself. Quercetin metabolites are able to strongly displace warfarin from HSA suggesting that high quercetin doses can strongly interfere with warfarin therapy. On the other hand, tested flavonoids showed no or weaker inhibition of CYP2C9 compared to warfarin, making it very unlikely that quercetin or its metabolites can significantly inhibit the CYP2C9-mediated inactivation of warfarin.

Development of a User-Friendly App for Assisting Anticoagulation Treatment

Blood coagulation time is an important factor to consider for postoperative and cardiac disorder patients who have been prescribed anticoagulant coagulant medications. This chapter describes a patient self-management system for assessment of blood coagulation times and determining appropriate anticoagulant dosages using a test strip device and the Coagu app. This app can also be used as a patient reminder of treatment times and to monitor treatment and effects over time.