Costs and consequences of clopidogrel versus aspirin for secondary prevention of ischaemic events in (high-risk) atherosclerotic patients in Sweden: a lifetime model based on the CAPRIE trial and high-risk CAPRIE subpopulations

Cost-Effectiveness of Clopidogrel vs Aspirin Monotherapy After Percutaneous Coronary Intervention: Results From the HOST-EXAM Study

Background

The HOST-EXAM (Harmonizing Optimal Strategy for Treatment of Coronary Artery Disease-Extended Antiplatelet Monotherapy) trial showed superior efficacy and safety of clopidogrel monotherapy compared with aspirin monotherapy during the chronic maintenance period after percutaneous coronary intervention (PCI).

Objectives

The goal of this study was to investigate the cost-effectiveness of clopidogrel monotherapy compared with that of aspirin monotherapy.

Methods

A Markov model was developed for patients in the stable phase after PCI. From the perspectives of the South Korean, UK, and U.S. health care systems, the lifetime health care costs and quality-adjusted life-years (QALYs) of each strategy were estimated. Transition probabilities were obtained from the HOST-EXAM trial, and health care costs and health-related utilities were obtained from data and literature for each country.

Results

From the perspective of the South Korean health care system, the base-case analysis showed that clopidogrel monotherapy was $3,192 higher in lifetime health care costs and 0.139 lower in QALYs compared with aspirin. This result was greatly influenced by the numerically but insignificantly higher cardiovascular mortality of clopidogrel compared with aspirin. In the analogous UK and U.S. models, clopidogrel monotherapy was projected to decrease health care costs by £1,122 and $8,920 per patient compared with aspirin monotherapy while reducing QALYs by 0.103 and 0.175, respectively.

Conclusions

Based on empirical data from the HOST-EXAM trial, clopidogrel monotherapy was projected to lead to reduced QALYs compared with aspirin during the chronic maintenance period after PCI. These results were affected by a numerically higher rate of cardiovascular mortality in clopidogrel monotherapy reported from the HOST-EXAM trial. (Harmonizing Optimal Strategy for Treatment of Coronary Artery Stenosis-Extended Antiplatelet Monotherapy [HOST-EXAM]; NCT02044250).

Cost-effective analysis of clopidogrel versus aspirin for high risk patients with established peripheral arterial disease in China

Objective: To assess the cost-effectiveness of clopidogrel versus aspirin for high risk patients (pre-existing symptomatic atherosclerosis or multi-vascular territory involvement) with established peripheral arterial disease (PAD) for secondary prevention of atherothrombotic events in a Chinese setting.Methods: A Markov model with a lifetime horizon was developed from the perspective of the national healthcare system in China. The primary outputs are quality adjusted life years (QALYs), direct medical costs, and the incremental cost-effectiveness ratios (ICERs). Clinical efficacy data were obtained from the CAPRIE trial. Drug acquisition cost, other direct medical costs, and utilities were from pricing records and the literature. One-way sensitivity analysis and probabilistic sensitivity analysis (PSA) were conducted to test the robustness of the model on all parameters.Results: In patients with pre-existing atherosclerosis, 2 years of treatment with clopidogrel and aspirin would yield total QALYs of 8.776 and 8.576 at associated costs of ¥18,777 ($2,838) and ¥12,302 ($1,859), respectively, resulting in an ICER of ¥32,382 ($4,893) per QALY gained. In patients with PVD, secondary prevention with the same drugs would expect to lead to total QALYs of 8.836 and 8.632 at associated costs of ¥18,518 ($2,798) and ¥12,041 ($1,820), respectively, resulting in a corresponding ICER of ¥31,743 ($4,797) per QALY gained. The results were most sensitive to the discount rate for future outcomes and costs. The PSA indicated that the probability of clopidogrel being cost-effective was 100% at the willingness-to-pay threshold of 3-times GDP.Conclusions: Secondary prevention with clopidogrel is an attractive cost-effective option compared with aspirin for high risk patients with established PAD from the perspective of the national healthcare system in Chinese settings.

Comparison Between Aspirin and Clopidogrel in Secondary Stroke Prevention Based on Real-World Data

Background

Clopidogrel was thought to be superior to aspirin for secondary prevention of vascular diseases in clinical trials. In this study we assessed the safety and efficacy of clopidogrel versus aspirin in real‐world practice by using the Taiwan Stroke Registry.

Methods and Results

Patients with ischemic stroke (2006–2016) on aspirin or clopidogrel for secondary stroke prevention were identified in the Taiwan Stroke Registry. Stroke recurrence and mortality rates in patients receiving aspirin (N=34 679) were compared with those receiving clopidogrel (N=7611) during a 12‐month follow‐up period. Propensity score matching and conditional Cox proportional hazards regression model were applied to control confounding factors with 6443 patients in each group. After propensity score matching, stroke recurrence rates were comparable between groups, with 223 patients in the aspirin (3.46%) and 244 in the clopidogrel group (3.79%) (hazard ratio=1.13, 95% confidence interval=0.89–1.43, P=0.311). However, the mortality rate was significantly higher in the clopidogrel group (362 patients, 5.62%) than in the aspirin group (302 patients, 4.69%) (hazard ratio=1.30, 95% confidence interval=1.07–1.58, P=0.008). Results were consistent before and after propensity score matching.

Conclusions

Clopidogrel was as effective as aspirin for prevention of recurrent stroke in real‐world practice. However, the mortality rate was significantly higher in the clopidogrel than in the aspirin group.

Aspirin better than clopidogrel on major adverse cardiovascular events reduction after ischemic stroke: A retrospective nationwide cohort study

Background

Several clinical trials reported that clopidogrel was superior to aspirin in secondary stroke prevention by reducing the risk of major adverse cardiovascular events (MACE). We aimed to compare the efficacy of clopidogrel with aspirin in reducing one-year risk of MACE based on real-world evidence from Taiwan Health Insurance Database.

Methods

We identified ischemic stroke patients between 2000 and 2012 who took aspirin or clopidogrel within 7 days of stroke onset for 1-year follow-up. The primary outcome was one-year MACE including recurrent stroke, acute myocardial infarction, and death. Propensity score matching and conditional Cox proportional hazards regression were conducted to control the confounding factors.

Results

From 9,089 ischemic stroke patients, we found 654 patients on aspirin and 465 patients on clopidogrel who met the selective inclusion criteria. After propensity score matching, 379 patients were selected from each group. The clopidogrel group had a 1.78-fold MACE risk compared with the aspirin group at one-year follow-up (95% CI = 1.41–2.26, p<0.01). The MACE-free rate in the aspirin group was 15.74% higher than in the clopidogrel group at one-year follow-up. Sub-analysis of the three components of MACE showed that clopidogrel conferred higher risk of recurrent stroke (OR 1.43, 95% CI = 1.06–1.92, p 0.02) and acute myocardial infarction (OR 3.72, 95% CI = 1.04–13.3, p 0.04), but no different risk of death than that of aspirin.

Conclusions

Among first-ever ischemic stroke patients, secondary stroke prevention using clopidogrel was associated with higher rates of MACE than aspirin. Aspirin might have better efficacy in secondary stroke prevention and was associated with lower risk of MACE. The real-world evidence raises the need to re-assess the current therapeutic options in secondary stroke prevention applying aspirin vs. clopidogrel.

Modeling hard clinical end-point data in economic analyses

OBJECTIVE

The availability of hard clinical end-point data, such as that on cardiovascular (CV) events among patients with type 2 diabetes mellitus, is increasing, and as a result there is growing interest in using hard end-point data of this type in economic analyses. This study investigated published approaches for modeling hard end-points from clinical trials and evaluated their applicability in health economic models with different disease features.

METHODS

A review of cost-effectiveness models of interventions in clinically significant therapeutic areas (CV diseases, cancer, and chronic lower respiratory diseases) was conducted in PubMed and Embase using a defined search strategy. Only studies integrating hard end-point data from randomized clinical trials were considered. For each study included, clinical input characteristics and modeling approach were summarized and evaluated.

RESULTS

A total of 33 articles (23 CV, eight cancer, two respiratory) were accepted for detailed analysis. Decision trees, Markov models, discrete event simulations, and hybrids were used. Event rates were incorporated either as constant rates, time-dependent risks, or risk equations based on patient characteristics. Risks dependent on time and/or patient characteristics were used where major event rates were >1%/year in models with fewer health states (<7). Models of infrequent events or with numerous health states generally preferred constant event rates.

LIMITATIONS

The detailed modeling information and terminology varied, sometimes requiring interpretation.

CONCLUSIONS

Key considerations for cost-effectiveness models incorporating hard end-point data include the frequency and characteristics of the relevant clinical events and how the trial data is reported. When event risk is low, simplification of both the model structure and event rate modeling is recommended. When event risk is common, such as in high risk populations, more detailed modeling approaches, including individual simulations or explicitly time-dependent event rates, are more appropriate to accurately reflect the trial data.

Model performance evaluation (validation and calibration) in model-based studies of therapeutic interventions for cardiovascular diseases : a review and suggested reporting framework

Decision analytic models play an increasingly important role in the economic evaluation of health technologies. Given uncertainties around the assumptions used to develop such models, several guidelines have been published to identify and assess 'best practice' in the model development process, including general modelling approach (e.g., time horizon), model structure, input data and model performance evaluation. This paper focuses on model performance evaluation. In the absence of a sufficient level of detail around model performance evaluation, concerns regarding the accuracy of model outputs, and hence the credibility of such models, are frequently raised. Following presentation of its components, a review of the application and reporting of model performance evaluation is presented. Taking cardiovascular disease as an illustrative example, the review investigates the use of face validity, internal validity, external validity, and cross model validity. As a part of the performance evaluation process, model calibration is also discussed and its use in applied studies investigated. The review found that the application and reporting of model performance evaluation across 81 studies of treatment for cardiovascular disease was variable. Cross-model validation was reported in 55 % of the reviewed studies, though the level of detail provided varied considerably. We found that very few studies documented other types of validity, and only 6 % of the reviewed articles reported a calibration process. Considering the above findings, we propose a comprehensive model performance evaluation framework (checklist), informed by a review of best-practice guidelines. This framework provides a basis for more accurate and consistent documentation of model performance evaluation. This will improve the peer review process and the comparability of modelling studies. Recognising the fundamental role of decision analytic models in informing public funding decisions, the proposed framework should usefully inform guidelines for preparing submissions to reimbursement bodies.

P2Y12 receptor: platelet thrombus formation and medical interventions

Platelets express a wide range of receptors and proteins that play essential roles in thrombus formation. Among these, the P2Y(12) receptor, a member of the G protein-coupled receptor family, has attracted a significant amount of attention. Stimulation of the P2Y(12) receptor by ADP results in activation of various signaling pathways involved in amplification of platelet activation and aggregation. There have been extensive attempts to design an ideal antithrombotic agent to block P2Y(12), which shows selective expression, as an intervention for cardiovascular disease. Current inhibitors of the P2Y(12) receptor include indirect inhibitor members of the thienopyridine family (ticlopidine, clopidogrel, and prasugrel), and direct P2Y(12) inhibitors (ticagrelor, cangrelor and elinogrel). Of these, clopidogrel is the most commonly prescribed P2Y(12) blocker; however, this product does not fulfill the ideal therapeutic requirements. The main limitations of clopidogrel administration include slow onset, prevention of recovery of platelet functions, and interindividual variability. Hence, advanced studies have been carried out to achieve more efficient and safer P2Y(12) blockade. In this review, we provide a brief but comprehensive report on P2Y(12), its role on platelet thrombus formation, and the targeting of this receptor as an intervention for cardiovascular disease, for the benefit of basic science and clinical researchers.

Is it cost-effective to increase aspirin use in outpatient settings for primary or secondary prevention? Simulation data from the REACH Registry Australian Cohort

AIMS

To describe aspirin use in primary and secondary prevention and to determine the incremental costs-effectiveness ratio (ICER) per life year gain (LYG) of aspirin use among subjects with, or at high risk of atherothrombotic disease.

DESIGN AND SUBJECTS

To project the cost-effectiveness of aspirin over 5 years of follow-up, a Markov state transition model was developed with yearly cycles and the following health states: "Alive" (post-CAD) and "Dead." The model compared current coverage observed among 2361 subjects using the prospective Australian subset of Reduction of Atherothrombosis for continued Health (REACH) registry, and hypothetical situation whereby all subjects assumed to be treated. Costs were calculated based on the Australian government reimbursed data for 2010.

MAIN OUTCOME MEASURES

ICER per LYG for increased use of aspirin.

RESULTS

The use of aspirin in current group varied from 67% to 70%. The base-case analysis showed that increasing aspirin use among subjects with existing CAD in outpatient settings was cost saving, while increasing use of aspirin in primary prevention equated to an ICER of AUD 7126 per LYG.

CONCLUSION

Among subjects with existing CAD aspirin use was shown to be a dominant choice of treatment. However, among patients without existing cardiovascular disease (primary prevention), increased uptake of aspirin was cost effective but with uncertain benefit, with two hemorrhagic bleeding events occurring for every life saved.