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Economic benefits of amlodipine treatment in patients with coronary artery disease |
Casciano R, Doyle J J, Chen J, Arikian S, Casciano J, Kugel H, Arocho R |
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Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. Health technology The use of amlodipine for the treatment of patients with coronary artery disease (CAD).
Economic study type Cost-effectiveness analysis.
Study population The study population comprised the general population of patients with CAD.
Setting The setting was primary care. The economic study was carried out in USA.
Dates to which data relate The effectiveness evidence was derived from two studies published in 1999 and 2000. The dates during which the resource use data were obtained were not reported. The price year was 1999.
Source of effectiveness data The effectiveness data were derived from published studies.
Modelling A Markov model was constructed to estimate the expected outcomes and costs of a hypothetical cohort of patients with CAD. Cycles of 6 months over a time period of 3 years were considered. The patients moved across the following health states:
unstable angina,
unstable angina with coronary artery bypass graft (CABG),
unstable angina with percutaneous transluminal coronary angioplasty (PTCA)/stents/atherectomy,
myocardial infarction,
myocardial infarction with CABG,
myocardial infarction with PTCA/stents/atherectomy,
congestive heart failure,
stroke,
CABG,
PTCA/stents/atherectomy, and
death.
The cohort used in the decision model comprised 6,099,417 patients. It was derived using nationwide data extrapolated from a published study.
Outcomes assessed in the review The primary health outcomes estimated from the published studies were the transitional probabilities used in the decision model, the number of cardiovascular disease (CVD) events and hospitalisations, and data on the US population suffering from CAD.
Study designs and other criteria for inclusion in the review One of the primary studies was a randomised, placebo-controlled double-blinded trial involving 825 patients with CAD (PREVENT trial). The second study was a survey of a comprehensive cross-sectional sample of the health status of the US population (NASHES III), which was aimed at identifying patients with CAD.
Sources searched to identify primary studies Criteria used to ensure the validity of primary studies Methods used to judge relevance and validity, and for extracting data Number of primary studies included The effectiveness evidence was obtained from two primary studies.
Methods of combining primary studies The primary studies were combined using narrative methods.
Investigation of differences between primary studies Results of the review Most of the data derived from the published studies were not reported. There were 413 events in the cohort of patients treated with amlodipine and 455 among those who were administered placebo. The difference was statistically significant. This difference was evident as early as the first 6-month period.
Methods used to derive estimates of effectiveness The authors made some assumptions about the effectiveness data used in the decision model.
Estimates of effectiveness and key assumptions The authors assumed a 100% compliance rate with treatment over the 3-year period of the study. The other assumptions were intended to ensure a conservative analysis.
Measure of benefits used in the economic analysis No summary benefit measure was used in the analysis. A cost-consequences analysis was therefore conducted.
Direct costs A 3% discount rate was used since the costs were incurred during three years. The unit costs were only reported separately from the quantities of resources for some items. The cost items included in the analysis were inpatient costs, physician services and follow-up costs. The costs associated with each health state reported in the model were included. The cost/resource boundary adopted in the analysis was that of the third-party payer. The costs were estimated from the Healthcare Costs and Utilisation Project 3 (based on the relevant diagnosis-related group for the hospitalisation being considered), the Medicare-based physician fee schedule, and the Redbook. The authors made several assumptions in the cost analysis on the quantities of resources (mainly length of hospital stay and use of concomitant therapies). In particular, national estimates for average length of hospital stay and charges-per-discharge were used to approximate economic data. The price year was 1999.
Statistical analysis of costs The costs were treated deterministically in the base-case.
Indirect Costs The indirect costs were not included in the analysis.
Sensitivity analysis Several sensitivity analyses were conducted to assess the impact of several assumptions on the estimated costs. Univariate sensitivity analyses examined the influence of the cost of amlodipine. They also examined the probability values of several events such as the risk of hospitalisation due to unstable angina, PTCA or CABG. A Monte Carlo simulation (10,000 simulations) was performed, varying the cost data within +/- 10% of the initial values and probability values within the 95% confidence intervals. Finally, some scenario analyses were carried out to test the impact of key assumptions. For example, the use of medication other than amlodipine in both cohorts, drug compliance, the use of concomitant calcium-channel blockers, and the findings of the PREVENT External Events Classification Committee.
Estimated benefits used in the economic analysis See the 'Effectiveness Results' section.
Cost results The net present value of the expected per patient costs over the 3-year period of the analysis was $14,117 for amlodipine and $16,683 for placebo patients. The population-based analysis showed that the current medical costs associated with CVD events in the US population of patients with CAD were approximately $32 billion per year. The estimated costs were robust to variations carried out in all the sensitivity analyses. None of the alternative scenarios favoured placebo patients.
Synthesis of costs and benefits Irrelevant as a cost-consequences analysis was conducted.
Authors' conclusions The use of amlodipine to prevent the progression of coronary artery disease (CAD) was both effective in reducing hospitalisations and the episodes of revascularisation. In addition, it was cost-saving in comparison with standard care, represented by patients who were administered placebo in the USA.
CRD COMMENTARY - Selection of comparators The rationale for the choice of the comparator was clear. Placebo was selected, as it represented the main comparator of the study drug in the primary study from which the effectiveness data were obtained. You should decide whether it represents a valid comparator in your own setting.
Validity of estimate of measure of effectiveness The effectiveness analysis used data derived from published studies, but a formal review of the literature was not undertaken. In addition, the data were combined using narrative methods. The authors reported the design and the characteristics of the primary studies involved in the analysis. As the emphasis of the study was on the costs, a measure of effectiveness related to patient health was not derived since the outcomes assessed were basically used as indicators of resource use.
Validity of estimate of measure of benefit No summary benefit measure was used in the economic analysis. The analysis was therefore categorised as a cost-consequences study.
Validity of estimate of costs The cost analysis was conducted from the perspective of the third-party payer in the USA. It appears that all the relevant categories of costs have been included in the study. Details on the cost data were reported and the price year was given, thus enabling the study to be reproduced in other settings. The unit costs were only reported separately from the quantities of resources for some items. The costs were treated deterministically in the base-case, but few sensitivity analyses were conducted. The validity of the economic analysis was mainly limited by several assumptions about the quantities of resources used.
Other issues The authors made few comparisons of their findings with those from other studies. The issue of the generalisability of the study results to other settings was not addressed. However, several sensitivity analyses were conducted and reported in detail, thus enhancing the external validity of the analysis. The authors discussed the impact of possible limitations of their analysis. These were mainly related to the assumptions made in the economic evaluation, which were required due to the lack of actual data measured alongside the trial. However, the authors also pointed out that the estimated costs were robust to variations in most of the assumptions made in the decision model.
Implications of the study The authors suggest that decision-makers should consider amlodipine as an agent of choice in patients with CAD. Future longer-term studies should be carried out to better assess the potential cost-savings and benefits of amlodipine and similar treatments.
Source of funding Supported by a grant from Pfizer Inc., New York (NY), USA.
Bibliographic details Casciano R, Doyle J J, Chen J, Arikian S, Casciano J, Kugel H, Arocho R. Economic benefits of amlodipine treatment in patients with coronary artery disease. PharmacoEconomics 2002; 20(8): 553-563 Indexing Status Subject indexing assigned by NLM MeSH Amlodipine /economics /therapeutic use; Calcium Channel Blockers /economics /therapeutic use; Coronary Artery Disease /complications /drug therapy /economics; Cost Savings; Female; Humans; Male; Markov Chains; Models, Economic; Prospective Studies AccessionNumber 22002008214 Date bibliographic record published 31/05/2003 Date abstract record published 31/05/2003 |
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