Warfarin in the secondary prevention of thromboembolism in atrial fibrillation: impact of bioavailability on costs and outcomes

Cost of atrial fibrillation: invasive vs non-invasive management in 2012

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia. It places an enormous burden on the patients, caregivers and the society at large. As a chronic illness, AF accrues significant costs related to clinical presentation, complications and loss of productivity. Novel invasive approaches to AF promise a cure in some patients and a significant reduction in AF burden in others, but are very expensive. This paper will address the cost of conventional and invasive strategies in AF care and will review the evidence on the comparative cost effectiveness of these approaches.

A review of the cost of atrial fibrillation

OBJECTIVES

To systematically review and synthesize the literature on the costs of atrial fibrillation (AF) with attention to study design and costing methods, geography, and intervention approaches.

METHODS

A systematic search for previously published studies reporting the costs for AF patients was conducted. Data were analyzed in three steps: first by evaluating overall system costs; second by evaluating the relative contribution of specific cost components; and third by examining variations across study designs, across primary treatment approach, and by geography. Finally, a specific review of the treatment costs associated with anticoagulation treatment was examined given the clinical importance and attention given to these costs in the literature.

RESULTS

The literature search resulted in 115 articles. On review of the abstracts or full text of these articles, 21 articles met all study criteria and reported on health system AF-related direct costs. A further six articles focused exclusively on anticoagulation costs for patients with AF. The overall average annual system cost across 27 estimates obtained from the literature was $5450 (SD = $3624) in 2010 Canadian dollars and ranged from a low of $1,632 to a high of $21,099. About one-third of these costs could be attributed to anticoagulation management. The largest cost component was acute care, followed by outpatient and physician and then medication-related costs.

CONCLUSION

AF-related medical costs are high, reflecting resource-intensive and long-term treatments including anticoagulation treatment. These costs, accompanied with increasing prevalence, justify increased attention to the management of patients with AF. Future studies of AF cost should ensure a broad assessment of the incremental direct medical and societal cost associated with this diagnosis.

Hemorrhagic and thrombotic events associated with generic substitution of warfarin in patients with atrial fibrillation: a retrospective analysis

BACKGROUND

Substitution of generic warfarin for imprint warfarin (Coumadin; DuPont/Bristol-Myers Squibb) has been a controversial issue due to bioavailability and bioequivalence concerns.

OBJECTIVE

To assess the risk of thrombotic and hemorrhagic events following substitution of warfarin formulations in patients with atrial fibrillation (AF).

METHODS

Historical cohort analysis was performed using a commercial insurance claims database. Adults with a diagnosis of AF between January 2003 and December 2007, with 16 or more months of continuous eligibility, a warfarin prescription within 30 days after index AF diagnosis, and at least 3 warfarin prescription fills during the follow-up period were included. Individuals with AF diagnosis or warfarin prescription during the pre-index period were excluded. Cox proportional hazard regression models controlling for sex and baseline comorbidities (Charlson comorbidity index, CCI) were used to evaluate the risks of thrombotic and hemorrhagic events following warfarin formulation switches.

RESULTS

Of 37,756 subjects included in the analysis (mean age 70.96 years, 42.3% females), 12,996 (34.4%) switched warfarin formulations, 20,292 (53.7%) used only 1 generic product, and 4468 (11.8%) used only Coumadin during follow-up. Compared with continued use of Coumadin, switching from that product to the generic formulation was associated with a significantly higher risk of thrombotic events (HR = 1.81; 95% CI 1.42 to 2.31). Similar findings were observed for switching from generic warfarin to Coumadin (HR = 1.76; 95% CI 1.35 to 2.30), and from 1 generic to another generic product (HR = 1.89; 95% CI 1.57 to 2.29). Similarly, switching from Coumadin to generic warfarin (HR = 1.51; 95% CI 1.17 to 1.93), generic warfarin to Coumadin (HR = 1.60; 95% CI 1.23 to 2.1), and from 1 generic to another generic product (HR = 1.74; 95% CI 1.45 to 2.11) were associated with significantly higher risk of hemorrhage than remaining on Coumadin.

CONCLUSIONS

Switching warfarin formulations exposed patients with AF to a higher risk of bleeding events compared to remaining on a single product. Maintaining patients on a product with consistent bioavailability may optimize the risk-benefit balance of anticoagulation therapy.

How much does international normalized ratio monitoring cost during oral anticoagulation with a vitamin K antagonist? A systematic review

Next-generation oral anticoagulants offer the potential for effective prevention and treatment of thrombosis without the need for repeated monitoring of the international normalized ratio (INR). This systematic review evaluated the costs associated with INR monitoring tests performed as part of the standard management of oral anticoagulation with vitamin K antagonists. Studies published in or after 1990 reporting the costs of INR monitoring were identified from bibliographic databases and manual searches of reference lists. Cost data were extracted and inflated to the year 2006 before purchasing power parity conversion to US dollars. A total of 29 studies reported the cost of one INR test, which was shown to range from $6.19 to $145.70. Cost estimates were based on various combinations of direct medical costs, such as healthcare contacts, equipment, laboratory tests, clerical costs (postage and stationery), telephone calls, quality control, training/education and patient transportation, and indirect costs, such as time lost from work. In conclusion, the cost of INR monitoring varied substantially between studies depending on the monitoring modality and setting, and the cost categories included. When selecting a published estimate, healthcare decision makers should ensure that the chosen estimate reflects local service provision as closely as possible.

Costs of stroke using patient-level data: a critical review of the literature

BACKGROUND AND PURPOSE

With decision-analytic models becoming more popular to assess the cost-effectiveness of health care interventions, the need for robust estimates on the costs of cerebrovascular disease is paramount. This study reports the results from a literature review of the costs of cerebrovascular diseases, and assesses the quality of the published evidence against a set of defined criteria.

METHODS

A broad literature search was conducted. Those studies reporting mean/median costs of cerebrovascular diseases derived from patient-level data in a developed country setting were included. Data were abstracted using standardized reporting forms and assessed against 4 predefined criteria: use of adequate methodologies, use of a population-based study, inclusion of premorbid resource use, and reporting of costs by different patient subgroups.

RESULTS

A total of 120 cost studies were identified. The cost estimates of stroke were compared by taking into account the effects of inflation and price differentials between countries. Average costs of stroke ranged from $468 to $146 149. Differences in costs were also found within country, with estimates in the USA varying 20-fold. Although the costing methodologies used were generally appropriate, only 5 studies were based on population-based studies, which are the gold standard study design when comparing incidence, outcome, and costs.

CONCLUSIONS

This review showed large variations in the costs of stroke, mainly attributable to differences in the populations studied, methods, and cost categories included. The wide range of cost estimates could lead to selection bias in secondary health economic analyses, with authors including those costs that are more likely to produce the desired results.

Cost Comparison of Catheter Ablation and Medical Therapy in Atrial Fibrillation

INTRODUCTION

There is emerging evidence for clinical superiority of catheter ablation over rate and rhythm control strategies in paroxysmal atrial fibrillation (PAF). The objective of this study was to compare costs related to medical therapy versus catheter ablation for PAF in Ontario (Canada).

METHODS

Costs related to medical therapy in the analysis included the cost of anticoagulation, rate and rhythm control medications, noninvasive testing, physician follow-up visits, and hospital admissions, as well as the cost of complications related to this management strategy. Costs related to catheter ablation were assumed to include the cost of the ablation tools (electroanatomic mapping or intracardiac echocardiography-guided pulmonary vein ablation), hospital and physician billings, and costs related to periprocedural medical care and complications. Costs related to these various elements were obtained from the Canadian Registry of Atrial Fibrillation (CARAF), government fee schedules, and published data. Sensitivity analyses looking at a range of initial success rates (50-75%) and late attrition rates (1-5%), prevalence of congestive heart failure (CHF) (20-60%), as well as discounting varying from 3% to 5% per year were performed.

RESULTS

The cost of catheter ablation ranged from $16,278 to $21,294, with an annual cost of $1,597 to $2,132. The annual cost of medical therapy ranged from $4,176 to $5,060. Costs of ongoing medical therapy and catheter ablation for PAF equalized at 3.2-8.4 years of follow-up.

CONCLUSION

Catheter ablation is a fiscally sensible alternative to medical therapy in PAF with cost equivalence after 4 years.

Cost-effectiveness of catheter ablation for atrial fibrillation

PURPOSE OF REVIEW

Catheter ablation for atrial fibrillation is a rapidly evolving field. It has been adopted at many institutions worldwide. This review compares the efficacy and cost of catheter ablation and medical therapy in atrial fibrillation patients.

RECENT FINDINGS

There is emerging evidence for clinical superiority of catheter ablation over medical therapy for restoring and maintaining sinus rhythm in atrial fibrillation patients. Early analyses of costs related to catheter ablation in atrial fibrillation suggest that medical therapy and catheter ablation become cost-equivalent at about 5 years of follow-up. A recent cost-effectiveness study concluded that catheter ablation is a cost-effective alternative to medical care in younger and older patients at low and moderate risk of stroke, assuming that restoration and maintenance of sinus rhythm with ablation would have some protective effect with respect to embolic events.

SUMMARY

Catheter ablation is a potentially cost-effective strategy in select patients with atrial fibrillation. Long-term randomized studies that compare it to conventional care and focus on outcomes of morbidity and mortality are necessary prior to widespread application of this technique.

Are brand-name and generic warfarin interchangeable? Multiple n-of-1 randomized, crossover trials

BACKGROUND

Warfarin is a commonly used anticoagulant in North America. Several generic formulations have been approved, raising concern over the safety and efficacy of these products compared with brand-name Coumadin.

OBJECTIVE

To ensure that generic warfarin products can be safely interchanged with Coumadin.

METHODS

Multiple n-of-1 randomized, double-blind, crossover trials switched outpatients (N = 7) between a generic warfarin formulation (Apo-warfarin) and Coumadin over 30 weeks. Study patients took each drug for five 3-week periods, with international normalized ratio (INR) measurements taken twice per period. Inter- and intrapatient differences between generic warfarin and Coumadin were compared, and overall study patient results were compared with those of a Coumadin control group.

RESULTS

There were no differences between warfarin products in terms of mean INR results or number of dosage adjustments required. There also was no difference in INR variation based on warfarin formulation (p > 0.69), nor was a patient and warfarin interaction found (p > 0.81). The INR results were not influenced by whether patients were maintained on Coumadin only (control group) or interchanged between Coumadin and generic warfarin (p = 0.98).

CONCLUSIONS

It appears that patients can safely and effectively switch between generic warfarin and Coumadin.