Warfarin therapeutic monitoring: is 70% time in the therapeutic range the best we can do?

Real-life contemporary vitamin K antagonist is still associated with very low time in therapeutic range despite strict international normalized ratio monitoring: Results of big data analysis

WHAT IS KNOWN AND OBJECTIVE

This study aimed to determine the results of INR monitoring in patients on vitamin K antagonists (VKAs) and the time in therapeutic range (TTR) in 'real-world' settings.

METHODS

Retrospective analysis of 836,857 INR measurements performed in adults from February 2010 to August 2015 in two districts in the French Brittany region.

RESULTS

Of the 836,857 INR measurements, 94.9% were ordered by general practitioners and 2.0% by cardiologists. The number of tests increased by 10-year age categories up to the age-group of 80-90 years. The number of INR measurements increased from 169,636 in 2011 to 176,184 in 2012, but then decreased slightly to 162,597 in 2013 and 164,427 in 2014. Mean coefficient of variation of INR was 19.0%, and mean TTR was 29.0%. TTR was higher in women than in men (31% vs. 18%), in older than in younger patients (19.1% at 40 years and 38.6% at 100 years) and in patients with arrhythmias than in those with deep vein thrombosis/pulmonary embolism (44.4% versus 19.4%) (p < 10^-5 for each comparison). Median interval between INR measurements was 14 days [7-28]; it was prolonged in men vs women, rural vs urban regions, older vs younger patients and when requested by GPs vs cardiologists. The interval was shorter for patients with INR outside the therapeutic range versus patients with INR within the therapeutic range (9 days [5-21] vs. 18 days [10-29], p < 10^-10 ).

WHAT IS NEW AND CONCLUSION

VKAs are still frequently prescribed in this era of direct oral anticoagulants. The low TTR cannot be explained by inadequate INR monitoring.

LRP1 and APOA1 Polymorphisms: Impact on Warfarin International Normalized Ratio-Related Phenotypes

Warfarin international normalized ratio (INR)-related phenotypes such as the percentage of INR time in the therapeutic range (PTTR) and INR variability are associated with warfarin adverse reactions. However, INR-related phenotypes greatly vary among patients, and the underlying mechanism remains unclear. As a key cofactor for coagulation proteins, vitamin K can affect warfarin INR values. The aim of this study was to address the influence of vitamin K-related single-nucleotide polymorphisms (SNPs) on warfarin INR-related phenotypes. A total of 262 patients who were new recipients of warfarin therapy and followed up for 3 months were enrolled. Twenty-nine SNPs were genotyped by matrix-assisted laser desorption/ionization time-of-flight mass array. Sixteen warfarin INR-related phenotypes were observed. After association analysis, 11 SNPs were significantly associated with at least one INR-related phenotype, and 6 SNPs were associated with at least 2 INR-related phenotypes (P < 0.05). In these SNPs, rs1800139, rs1800154, rs1800141, and rs486020 were the most representative. rs1800139, rs1800154, and rs1800141 locate in LRP1 and were found to be correlated with 1-month and 2-month INR variability (P < 0.05). Besides, the APOA1 rs486020 was significantly associated with the first month PTTR (P = 0.009), and patients with C-allele had higher PTTR than those with G-alleles almost during the entire monitoring period. In conclusion, the study revealed that the polymorphisms of LRP1 and APOA1 gene may play important roles in the variation of warfarin INR-related phenotypes. Our results provide new information for improving warfarin anticoagulation management.

Evaluation of a Health Information Technology-Enabled Panel Management Platform to Improve Anticoagulation Control in a Low-Income Patient Population: Protocol for a Quasi-Experimental Design

BACKGROUND

Warfarin is one of the most commonly prescribed medications in the United States, and it causes a significant proportion of adverse drug events. Patients taking warfarin fall outside of the recommended therapeutic range 30% of the time, largely because of inadequate laboratory monitoring and dose adjustment. This leads to an increased risk of blood clots or bleeding events. We propose a comparative effectiveness study to examine whether a technology-enabled anticoagulation management program can improve long-term clinical outcomes compared with usual care.

OBJECTIVE

Our proposed intervention is the implementation of an electronic dashboard (integrated into a preexisting electronic health record) and standardized workflow to track patients' laboratory results, identify patients requiring follow-up, and facilitate the use of a validated nomogram for dose adjustment. The primary outcome of this study is the time in therapeutic range (TTR) at 6 months post intervention (a validated metric of anticoagulation quality among patients receiving warfarin).

METHODS

We will employ a pre-post quasi-experimental design with a nonequivalent usual-care comparison site and a difference-in-differences approach to compare the effectiveness of a technology-enabled anticoagulation management program compared with usual care at a large university-affiliated safety-net clinic.

RESULTS

We used a commercially available health information technology (HIT) platform to host a registry of patients on warfarin therapy and create the electronic dashboard for panel management. We developed the intervention with, and for, frontline clinician users, using principles of human-centered design. This study is funded until September 2020 and is approved by the University of California, San Francisco Institutional Review Board until June 22, 2020. We completed data collection in September 2019 and expect to complete our proposed analyses by February 2020.

CONCLUSIONS

We anticipate that the intervention will increase TTR among patients taking warfarin and that the use of this HIT platform will facilitate tracking and monitoring of patients on warfarin, which could enable outreach to those overdue for visits or laboratory monitoring. We will use these findings to iteratively improve the platform in preparation for a larger, multiple-site, pragmatic clinical trial. If successful, our study will demonstrate the integration of HIT platforms into existing electronic health records to improve patient care in real-world clinical settings.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/13835.

Anticoagulant plus antiplatelet therapy for atrial fibrillation : Cost-utility of combination therapy with non-vitamin K oral anticoagulants vs. warfarin

BACKGROUND

Emerging evidence indicates combination therapy with anticoagulants and antiplatelet agents for atrial fibrillation (AF) will be increasingly required. Numerous studies compare the efficacy and cost-effectiveness of anticoagulation alone in AF, i. e., non-vitamin K oral anticoagulants (NOACs) vs. warfarin. However, the addition of antiplatelet agents with their potential for decreasing thromboembolic stroke counter-balanced by an increased bleeding risk has received less attention. Thus, we evaluated the cost-utility of this combination therapy.

METHOD AND RESULTS

We obtained event estimates from our recent meta-analysis of four randomized clinical trials designed to compare NOACs with warfarin in patients with AF. We examined patient subgroups within each trial that received antiplatelet therapy in addition to anticoagulation. Utilities were derived from the literature and cost estimates from the German health-care system. A decision tree was constructed and populated with these parameters. We used a 1-year time horizon because combination therapy is not recommended beyond this time. We calculated the incremental cost-effectiveness ratio (ICER) per quality-adjusted life-year (QALY). The derived ICER was 13,168.50 € per QALY. NOAC prices exerted considerable influence on the calculation. Nevertheless, there is potential for ICER shifts in favor of warfarin, e.g., if warfarin-mediated anticoagulation control is improved and thereby adverse events decrease. Conversely, if NOAC adherence decreases, adverse events could increase.

CONCLUSION

The derived ICER was 13,168.50 € per QALY, consistent with NOACs being cost-effective vs. warfarin when anticoagulation is used with antiplatelet agents. Nevertheless, country-, practice-, and patient-related factors influence the ICER. Our cost-utility calculation should be used a starting point for decision-making.

Designing and Implementing an Electronic Patient Registry to Improve Warfarin Monitoring in the Ambulatory Setting

BACKGROUND

Warfarin requires individualized dosing and monitoring in the ambulatory setting for protection against thromboembolic disease. Yet in multiple settings, patients spend upwards of 30% of time outside the therapeutic range, subjecting them to an increased risk of adverse events. At an urban, publicly funded clinic, the electronic health record (EHR) would not support integration with extant warfarin management software, which led to the creation and implementation of an electronic patient registry and a complementary team-based work flow to provide real-time health-system-level data for warfarin patients.

METHODS

Creation of the registry, which began in August 2014, entailed use of an existing platform, which could interface with the outpatient EHR. The registry was designed to help ensure regular testing and monitoring of patients while enabling identification of patients and subpopulations with suboptimal management. The work flow used for the clinic's warfarin patients was also redesigned. An assessment indicated that the registry identified 341 (96%) of 357 patients actively seen in the clinic.

RESULTS

For the cohort of the 357 patients in the registry, the no-show rate decreased from 31% (preimplementation, August 2014-December 2014) to 21% (postimplementation, January 2015-November 2015). The ratio of visits to no-shows increased from 2.3 to 4.0 visits.

CONCLUSION

Design and implementation of an electronic registry in conjunction with a complementary work flow established an active tracking system that improved treatment monitoring for patients on anticoagulation therapy. Registry creation also facilitated assessment of the quality of care and laid the groundwork for ongoing evaluation and quality improvement efforts.

Major bleeding risk among non-valvular atrial fibrillation patients initiated on apixaban, dabigatran, rivaroxaban or warfarin: a "real-world" observational study in the United States

BACKGROUND

Limited data are available about the real-world safety of non-vitamin K antagonist oral anticoagulants (NOACs).

OBJECTIVES

To compare the major bleeding risk among newly anticoagulated non-valvular atrial fibrillation (NVAF) patients initiating apixaban, warfarin, dabigatran or rivaroxaban in the United States.

METHODS AND RESULTS

A retrospective cohort study was conducted to compare the major bleeding risk among newly anticoagulated NVAF patients initiating warfarin, apixaban, dabigatran or rivaroxaban. The study used the Truven MarketScan(®) Commercial & Medicare supplemental US database from 1 January 2013 through 31 December 2013. Major bleeding was defined as bleeding requiring hospitalisation. Cox model estimated hazard ratios (HRs) of major bleeding were adjusted for age, gender, baseline comorbidities and co-medications. Among 29 338 newly anticoagulated NVAF patients, 2402 (8.19%) were on apixaban; 4173 (14.22%) on dabigatran; 10 050 (34.26%) on rivaroxaban; and 12 713 (43.33%) on warfarin. After adjusting for baseline characteristics, initiation on warfarin [adjusted HR (aHR): 1.93, 95% confidence interval (CI): 1.12-3.33, P=.018] or rivaroxaban (aHR: 2.19, 95% CI: 1.26-3.79, P=.005) had significantly greater risk of major bleeding vs apixaban. Dabigatran initiation (aHR: 1.71, 95% CI: 0.94-3.10, P=.079) had a non-significant major bleeding risk vs apixaban. When compared with warfarin, apixaban (aHR: 0.52, 95% CI: 0.30-0.89, P=.018) had significantly lower major bleeding risk. Patients initiating rivaroxaban (aHR: 1.13, 95% CI: 0.91-1.41, P=.262) or dabigatran (aHR: 0.88, 95% CI: 0.64-1.21, P=.446) had a non-significant major bleeding risk vs warfarin.

CONCLUSION

Among newly anticoagulated NVAF patients in the real-world setting, initiation with rivaroxaban or warfarin was associated with a significantly greater risk of major bleeding compared with initiation on apixaban. When compared with warfarin, initiation with apixaban was associated with significantly lower risk of major bleeding. Additional observational studies are required to confirm these findings.

International Normalized Ratio Variability: A Measure of Anticoagulation Quality or a Powerful Mortality Predictor

BACKGROUND

As atrial fibrillation (AF) carries twice the mortality hazard when compared with a similar population without diagnosed AF, the importance of risk stratifying is obvious. Several variables are related to outcome: age, comorbidities, and use of several medications, particularly oral anticoagulants. The CHA2DS2VASc score is an extremely useful tool to predict thromboembolic events and also mortality. The international normalized ratio (INR) variability is a treatment efficacy variable also associated with morbidity in patients receiving warfarin. The objective of the study is to compare the prognostic value of the CHA2DS2VASc versus the INR variability or its combination to predict mortality.

METHODS

In this observational study, we analyzed 589 patients from our Atrial Fibrillation Cohort, all on warfarin for more than 1 year and had more than 5 INRs performed in the last 2 years. The CHA2DS2VASc, HAS-BLED, and SAMe-TT2R2 scores were calculated as well as the INR variability using the time-in-therapeutic-range (TTR), the percentage of INRs (%INRs) within range, and the standard deviation of the INRs (SDINRs). Kaplan-Meier survival curves were plotted via different cutoff points.

RESULTS

The mean TTR was 53 ± 23%; 34.6% of the patients had a TTR above 64%. The mean %INRs in range was 50.2 ± 20.2; 17.3% of the population had %INRs in range above 70%. The mean SDINRs was .84 ± .54, and 38.4% had SDINRs below .79. Of 598, 139 (22%) discontinued warfarin treatment. Death was responsible for almost 50% of treatment discontinuation. Of 598, 68 patients died during the study period (11.5 %); the most frequent causes of death were heart failure (30%), bleeding (17%), and ischemic stroke (15%). Patient survival had a correlation with TTR, %INRs in range, SDINRs, left ventricular ejection fraction, CHA2DS2VASc, and the combination of CHA2DS2VASc + SDINRs (cutoff >1 and >.79, respectively).

CONCLUSIONS

INR variability is an extremely useful tool to assess anticoagulation quality. Calculation of both CHA2DS2VASc and INR variability appears to be extremely useful to predict mortality in patients with AF receiving warfarin. The SDINRs emerges as a strong mortality predictor compared to the other INR variability indexes.

Target-specific oral anticoagulants and the hospitalist

As a class, the target-specific oral anticoagulants (TSOACs) are at least as effective as warfarin, often with superior safety for the prevention of stroke in patients with nonvalvular atrial fibrillation (AF) and the treatment of acute venous thromboembolism (VTE) and prevention of recurrent VTE. Currently, dabigatran, the direct thrombin inhibitor, along with rivaroxaban and apixaban, direct factor Xa inhibitors, has been approved in multiple countries for these indications. Edoxaban, which has received approval for the abovementioned indications in Japan, has demonstrated efficacy and safety comparable to or better than warfarin in Phase III clinical trials and is under further regulatory consideration. It is anticipated that the use of TSOACs will increase as practitioners and healthcare systems gain familiarity with these drugs and adopt their use into clinical practice. This review will provide a brief overview of the TSOAC Phase III clinical trials for prevention of stroke and systemic embolic events in patients with AF and the Phase III clinical trials for the prevention of recurrent VTE, discuss current treatment guidelines, address how TSOACs may help meet national safety goals, and provide clinical decision-making guidance regarding the use of TSOACs for hospitalists.

Anticoagulation clinic versus a traditional warfarin management model

Warfarin is the most commonly prescribed oral anticoagulant. The management of warfarin is challenging, and current guidelines fail to include a model to assist practitioners in optimizing therapeutic dosing. The traditional model and the anticoagulation clinic (AC) model of warfarin management were compared and results found the AC model optimum.

The use of oral anticoagulants for the treatment of venous thromboembolic events in an ED

Venous thromboembolism (VTE) is a disease spectrum that ranges from deep vein thrombosis (DVT) to pulmonary embolism (PE). Rapid diagnosis and treatment of VTE by emergency care providers are critical for decreasing patient mortality, morbidity, and the incidence of recurrent events. Recent American College of Chest Physicians guidelines recommend initial treatment with unfractionated heparin, low-molecular weight heparin, or fondaparinux overlapped with warfarin for a minimum of 5 days for the treatment of VTE in most cases. Warfarin monotherapy is thereafter continued for 3, 6, or 12 months. These guidelines were published before the approval of target-specific oral anticoagulants (TSOACs), and they have yet to be updated to reflect these new treatment options. For some patients, TSOACs, which act by directly inhibiting factor IIa or factor Xa, may provide safer, more convenient alternatives to warfarin. Their advantages include ease of use, reduced monitoring requirements, and lower bleeding risk than traditional therapy. Additionally, clinical trials have established noninferiority of TSOACs to warfarin for the prevention of recurrent VTE. These trials have demonstrated that TSOACs exhibit similar or lower bleeding rates, particularly intracranial bleeding rates compared with warfarin. Anticoagulation therapy with TSOACs may allow early discharge or outpatient management options for low-risk patients with DVT and PE. This review addresses the importance of early diagnosis and treatment of VTE, outcomes of VTE risk assessment, key efficacy and safety data from phase 3 clinical trials for the various TSOACs for the treatment of DVT and PE, and the corresponding considerations for clinical practice.

Comparison of the phase III clinical trial designs of novel oral anticoagulants versus warfarin for the treatment of nonvalvular atrial fibrillation: implications for clinical practice

Although vitamin K antagonists (VKAs) have been the backbone of thromboprophylaxis in nonvalvular atrial fibrillation, their limitations have encouraged the development of a new generation of oral anticoagulants. This review compares the different designs and procedures used to conduct four phase III trials that tested dabigatran, rivaroxaban, apixaban, and edoxaban versus VKAs. Although pharmacologic characteristics and results of the main trials are briefly discussed, this review mainly focuses on study designs, enrollment criteria, populations studied, quality metrics, and transition strategies between oral anticoagulants. While each of the trials was of high quality, performed independently, and led by independent academic groups, substantial differences exist in terms of drug pharmacology and trial characteristics. Caution is advised when comparing results across trials as practicing clinicians strive to personalize anticoagulation treatments for their individual patients. We believe that the differences in the pharmacokinetic and pharmacodynamic profiles of the available novel oral anticoagulants (NOACs), coupled with substantial heterogeneity in the trial populations and designs and procedures used to conduct the trials, support an important role for each of the NOACs dependent upon the specific clinical scenario faced by the practicing clinician.

A prospective study on the use of warfarin in the United arab emirates

OBJECTIVES

The aims of this study were to evaluate adherence of patients and medical staff to warfarin guidelines and assess clinical outcome and predictors of treatment failure.

METHODS

This cross-sectional survey involved out- and in-patient subjects receiving warfarin. Patient attentiveness, compliance, co-morbidities, complications, and international normalized ratio (INR) as well as adherence of medical staff to established warfarin treatment guidelines were recorded.

RESULTS

One-hundred-sixty patients were recruited (mean ± SD age = 54 ± 1.3 years; 46% males; 77% overweight/obese). Indications for warfarin were atrial fibrillation (35%), deep vein thrombosis (28%), prosthetic heart valve (20%) and stroke or dilated cardiomyopathy (12%). "Warfarin booklets" were made available to 25% of the patients, and ~80% of the recipients reported inadequate understanding of its content. INR was strictly monitored in 23% of the patients; ~70% never received Information Leaflets; ~88% were unaware of warning labels; and ~58% were unaware that over-thecounter medications may affect warfarin. Therapeutic INR (2.9 ± 0.2; 76 days) was achieved in 73%; 20% had high INR (3.7 ± 0.1; 18.6 days) and 7% had low INR (1.6 ± 0.1; 16.7 days). Of the patients with high INR, 2.5% had major bleeding events. Of the patients with low INR, 5% had thromboembolic events. Poor compliance and co-morbidities were associated with adverse events (p=0.01).

CONCLUSIONS

Attentiveness and adherence to warfarin treatment and monitoring guidelines are suboptimal among patients and medical staff. Novel strategies are necessary to alert patients, pharmacists and physicians on the seriousness of warfarin treatment failure.