Original Articles |
From Christiana Care Health System (W.S.W., Zugui Zhang, P.K., C.J., J.B.), Newark, Del; Western New York Veterans Affairs Healthcare Network and Kaleida Health System (W.E.B.), Buffalo, NY; Emory University (Zefeng Zhang, E.V.), Atlanta, Ga; Mid-America Heart Institute/University of Missouri—Kansas City (J.A.S.), Kansas City, Mo; Cooperative Studies Program Coordinating Center (P.H.), VA Connecticut Healthcare System, West Haven, Conn; Vanderbilt University Medical Center (D.J.M.), Nashville, Tenn; San Antonio Veterans Affairs Medical Center (R.O.), San Antonio, Tex; Hartford Hospital (M.D.), Hartford, Conn; McMaster University (K.K.T., R.G.), Hamilton, Ontario, Canada; and Veterans Affairs Health Economics Resource Center (P.G.B.), Palo Alto, Calif.
Correspondence to William S. Weintraub, MD, John H. Ammon Chair and Director, Cardiology Section, Christiana Care Health System, 4755 Ogletown-Stanton Rd, Newark, DE 19718. E-mail wweintraub{at}christianacare.org
Received June 11, 2008; accepted July 10, 2008.
| Abstract |
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Methods and Results— Resource use was assessed by diagnosis-related group for hospitalizations and by current procedural terminology code for outpatient visits and tests and then converted to costs by use of 2004 Medicare payments. Medication costs were assessed with the Red Book average wholesale price. Life expectancy beyond the trial was estimated from Framingham survival data. Utilities were assessed by the standard gamble method. The incremental cost-effectiveness ratio was expressed as cost per life-year and cost per quality-adjusted life-year gained. The added cost of PCI was approximately $10 000, without significant gain in life-years or quality-adjusted life-years. The incremental cost-effectiveness ratio varied from just over $168 000 to just under $300 000 per life-year or quality-adjusted life-year gained with PCI. A large minority of the distributions found that medical therapy alone offered better outcome at lower cost. The costs per patient for a significant improvement in angina frequency, physical limitation, and quality of life were $154 580, $112 876, and $124 233, respectively.
Conclusions— The COURAGE trial did not find the addition of PCI to optimal medical therapy to be a cost-effective initial management strategy for symptomatic, chronic coronary artery disease.
Key Words: coronary disease angina epidemiology cost-benefit analysis stents
| Introduction |
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Editorial see p 4
Clinical Perspective p 20
| Methods |
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Patients with stable coronary artery disease were eligible for inclusion. Entry criteria included >70% stenosis in
1 major epicardial coronary artery with objective evidence of myocardial ischemia or
1 coronary stenosis >80% and classic angina without provocative testing.
Patients received aspirin and post-PCI clopidogrel in accordance with treatment guidelines.11 Patients received aggressive therapy for hyperlipidemia, hypertension, and angina. Lifestyle counseling focused on smoking cessation, physical activity, and dietary modification. Follow-up was for a minimum of 30 months.
The Seattle Angina Questionnaire (SAQ) was used to assess angina-specific health status at baseline and during follow-up. On the basis of the approach of Weintraub et al8 and Wyrwich et al,12 clinically significant improvements in SAQ scores were defined as
8-,
20-, and
16-point differences for the domains of physical limitation, angina frequency, and quality of life, respectively.
Economic Analysis Plan and Assessment of Cost
The economic analysis plan was to compare costs of each treatment arm and perform an incremental cost-effectiveness analysis.13,14 Costs included in the analysis were direct medical care costs for hospitalizations, pharmaceuticals, and outpatient care. Costs after the first year and life expectancy were discounted at 3% annually.11 The analysis used 2004 US dollars, with resource use and clinical outcomes from all 2287 patients.
Cardiovascular healthcare resource use associated with the index hospitalization and all follow-up hospitalizations was recorded prospectively. Resource utilization included (1) initial PCI (inpatient or outpatient), index hospitalization, or outpatient care other than PCI; (2) subsequent hospitalizations (including subsequent PCI); (3) medications, including 1 month of clopidogrel after PCI; (4) outpatient visits; and (5) cardiovascular tests during follow-up.
Initial and subsequent hospitalizations were assigned a diagnosis-related group as used in the US Medicare program by coders blinded to treatment group, in which coded variables were used. Costs for each diagnosis-related group were estimated with average Medicare reimbursement rates15,16 obtained from the Medicare Part A (MEDPAR) data file.17 Outpatient PCI, outpatient physician office visits and procedures, tests, or emergency room visits were coded by current procedural terminology and assigned a cost based on the Medicare fee schedule. The cost for outpatients was estimated by including the cost of a nursing home, intermediate-care facility, rehabilitation facility, outpatient visits, emergency visits, outpatient cardiac rehabilitation visits (cardiac-related visits only), home visits by nurses, and imaging for ischemia. All medications were assigned a cost based on the Red Book average wholesale price for lisinopril (for angiotensin-converting enzyme inhibitors), amiodarone (for antiarrhythmic drugs), warfarin (for anticoagulant drugs), simvastatin (for statins), metoprolol (for β-blockers), amlodipine (for calcium channel blockers), digoxin (for cardiac glycosides), hydrochlorothiazide (for diuretics), and isosorbide mononitrate (for nitrates). All changes in medications and utilities (see below) were assumed to have taken place midway between monitoring visits. The last year of in-trial cost in each treatment group was used to project future costs and utility beyond the trial. For lifetime cost, the average Medicare participant per capita expenditure of $5219 in 2004,17 together with the cost difference in the last 2 years between the 2 treatment groups, was used to estimate cost beyond the trial period. Nonparametric tests, including the Wilcoxon rank-sum test, were performed to compare costs and outcomes.
Utility and Life Expectancy Estimation
Quality-adjusted life-years (QALYs) were calculated by multiplying survival by utility, a measure of health status scaled from 0 (death) to 1 (perfect health). COURAGE used the U-Titer computer program to conduct the SAQ and to assess utility by standard gamble assessments.8 The U-Titer program is an automated, modular utility-assessment software package designed to implement the rating scale, category scaling, standard gamble, and chronic and temporary time tradeoff methods of assessing patients preferences. In addition to calculating utilities, the U-Titer program records information on the process experienced by the user. A multiple partial imputation strategy was used to estimate missing utility values.18 Utilities in COURAGE were comparable to the utilities of coronary disease in the Cost-effectiveness Analysis Registry,19 a reliable source of community utilities. Therefore, it was reasonable to assume that utilities assessed in COURAGE were consistent with community preferences for health states. The last year of utilities in each treatment group was used to project future utilities beyond the trial. It was assumed in lifetime analyses that for the first 2 years beyond the trial, the utility trend would follow trends in the last year of the study, but after that, the difference between the treatment groups would disappear.
Life expectancy for patients with and without nonfatal events was estimated from the Framingham Heart Study,20,21 a 40-year epidemiological study. The original Framingham Heart Study measured the potential burden of cardiovascular disease by transforming epidemiological measures into time-based life-years lost to or lived with the disease. Specifically, multistate life tables of the Framingham Heart Study cohort were used for all COURAGE patients to calculate expected survival for each patient in the study (Data Supplement Table I). Sex- and age-specific estimates of life-years lost because of events that occurred during the trial were obtained by subtracting life expectancy estimates for individuals with events from life expectancy estimates for individuals with coronary disease but without events.22 For patients who experienced multiple events of different types during the trial, lost life expectancy was estimated assuming a hierarchy of death, stroke, and myocardial infarction. For example, if a patient had stroke and myocardial infarction, the event of stroke would be used to estimate the lost life expectancy. These estimates were then applied to each patient in the COURAGE population, and average life-years lost was calculated for both treatment groups. The difference between treatment groups in average life-years lost because of events (death, stroke, and myocardial infarction) yielded an estimate of life-years gained with PCI. In-trial utility values were used to quality-adjust survival beyond the trial period.
Estimation of Cost-Effectiveness
The cost-effectiveness of PCI was expressed as the incremental cost-effectiveness ratio (ICER), defined as the additional cost of PCI divided by the life-years gained and QALYs gained. Bootstrap methods (5000 replicates) were used to estimate the 95% confidence intervals (CIs) for both cost and life-years gained with PCI.23 Traditional 1-way sensitivity analyses included varying life-years gained for the PCI group compared with the medical therapy group by 10% to 40%. Probabilistic sensitivity analysis was conducted to assess the impact of the simultaneous changes of all the variables involved in the cost and life-years gained.24 The probability assumptions of effectiveness were derived from American Heart Association statistics25 and the Cardiovascular Health Study.26 Monte Carlo simulation was performed to derive the differences in QALYs and mean cost between the 2 treatment groups. In addition, ICERs were calculated for 1 additional patient to have clinically significant improvement in angina frequency, physical functioning, and quality of life.
The authors had full access to the data and take full responsibility for the integrity of the data. All authors have read and agree to the manuscript as written.
| Results |
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Cost-Effectiveness Analysis, In-Trial and Lifetime
The point estimate for the in-trial ICER for PCI was $206 229 per QALY gained (Table 6). The frequency with which medical therapy dominated PCI and the absence of domination by PCI indicate considerable probability that medical therapy alone provided better clinical outcome at lower cost (Table 6; Figure 1A). A cost-effectiveness acceptability curve (Figure 1B) shows that the bootstrap-derived cost-effectiveness estimates were rarely <$50 000 per QALY gained, and a minority were <$100 000 per QALY gained.
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The characteristics of variables used in the probabilistic sensitivity analysis are shown in Table V in the Data Supplement. The distributional assumptions of the cost data were based on the actual data in the present study, and their ranges come from relevant sources.25,26
Figure 3A presents the contour plot of simulated distribution of mean differences in cost and effectiveness in QALYs based on the probabilistic sensitivity analysis over a lifetime. It reveals that the lifetime QALYs gained could range from -0.5 to 0.5 years for the PCI group compared with the medical therapy group, but the cost for the PCI group would always be significantly larger, varying from $4000 to $16 000. The ellipses indicate 50%, 95%, and 99% CIs of the simulated lifetime ICERs. The cost-effectiveness acceptability curve (Figure 3B) shows that even given the greater variation in this sensitivity analysis than noted purely by the play of chance in the base case (Figure 1A and 1B), there was only a 25% probability of PCI being cost-effective at the $50 000 threshold and a 41% probability at the $100 000 threshold. The probability of PCI being dominated by medical therapy was 43%.
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| Discussion |
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The cost for an improvement in symptoms is difficult to evaluate in cost-effectiveness analysis because it is difficult to compare the ICERs from such analysis to other forms of therapy for other disease states. Nonetheless, societal willingness to pay to improve angina for 1 year would almost certainly be a higher number than the willingness to pay for an additional QALY. Indeed, the approximately $150 000 for 1 patient to derive a clinically significant improvement in angina frequency with PCI would probably not meet a societal willingness-to-pay threshold. This analysis may be criticized because angina may not represent all benefits and risks of PCI compared with medical therapy, although it is generally considered to be the primary outcome improved by PCI. Although there were differences in angiographic nuclear perfusion surrogates, there were no other differences noted in clinical outcomes.7,27 Thus, health status, specifically angina, is a meaningful measure of outcome for cost-effectiveness analysis.
The cost-effectiveness of revascularization compared with medical therapy for chronic coronary artery disease has been studied previously. Weinstein and Stason28 developed a simulation based on the trials from the 1970s to early 1980s and found that coronary surgery offered a cost per QALY gained that ranged from $3800 in left main disease to $30 000 for single-vessel disease. Before any clinical trial data were available comparing PCI with medical therapy, Wong et al developed a simulation study that found balloon angioplasty to be cost-effective for severe angina.29 Claude et al30 evaluated revascularization in the elderly with PCI or coronary surgery as appropriate and found a cost of $6900 Euros per event averted. Although there have been 11 previous trials of PCI versus medical therapy, there have been no trial-based cost-effectiveness analyses of PCI relative to medical therapy.31
Study Limitations
Cost-effectiveness analysis is performed from a societal basis; however, costs are from a payer or provider perspective. It is also not generally possible to account for all costs. Diagnosis-related group–based costing is from a payer perspective and may not adequately account for resource utilization. Resource utilization in different healthcare systems may vary, and it is thus an assumption that costs from one healthcare system can be assigned equally to care provided in another healthcare system. Resource use beyond the trial period is based on a model, not on measurement. Also, projection of life expectancy and cost beyond the trial period must be based on models developed from the literature. Evaluation of utility, used to make quality adjustments for survival, is also problematic. Utility could only be measured in a minority of subjects, with data for the rest derived from statistical modeling. Despite the many limitations, the results of the present sensitivity analyses were robust.
Conclusions
The COURAGE trial did not find the addition of PCI to medical therapy to be a cost-effective initial management strategy for symptomatic, chronic coronary artery disease. The cost for 1 patient to have clinically significant improvement in angina for between 6 and 36 months8 exceeds $100 000. The economic outcomes in COURAGE are consistent with the clinical outcomes, which show that it is safe to defer PCI. The present analysis suggests that such an initial management strategy will achieve appreciable savings in health expenditures.
| Acknowledgments |
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This study was supported by the Cooperative Studies Program of the Department of Veterans Affairs Office of Research and Development, in collaboration with the Canadian Institutes for Health Research; unrestricted research grants were obtained from Merck & Co, Pfizer Pharmaceuticals, Bristol-Myers Squibb Medical Imaging, Fujisawa, Kos Pharmaceuticals, Data Scope, AstraZeneca, Key Pharmaceutical Co, Ltd, Sanofi-Aventis, Inc, First Horizon, and Nycomed Amersham. All industrial funding in support of the trial was directed through the Department of Veterans Affairs.
Disclosures
Dr Weintraub reports receiving consulting fees from Sanofi-Aventis, GlaxoSmithKline, Indigo Pharmaceuticals, and Cardiovascular Therapeutics and receiving grant support from Sanofi-Aventis, AstraZeneca, Otsuka, and Bristol-Myers Squibb. Dr Spertus reports receiving consulting fees from Otsuka and United Healthcare and grant support from Amgen, Bristol-Myers Squibb, Sanofi-Aventis, and Lilly. Dr Spertus holds a copyright to the Seattle Angina Questionnaire. Dr Jurkovitz reports receiving grant support from Bristol-Myers Squibb, Cardiovascular Therapeutics, Otsuka, Sanofi-Aventis, and AstraZeneca. Dr Boden reports receiving consulting fees from Pfizer, Merck, PDL Biopharma, Bristol-Myers Squibb, Abbott, and Cardiovascular Therapeutics and receiving lecture fees from Sanofi-Aventis, Kos Pharmaceuticals and Novartis. The remaining authors report no conflicts.
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| Footnotes |
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Guest Editor for this article was Eric D. Peterson, MD.
Clinical trial registration information—URL: http://www.clinicaltrials.gov. Unique identifier: NCT00007657.
The online-only Data Supplement is available with this article at http://circoutcomes.ahajournals.org/cgi/content/full/1/1/12/DC1.
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