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Cost-effectiveness of aspirin treatment in the primary prevention of cardiovascular disease events in subgroups based on age, gender, and varying cardiovascular risk |
Greving J P, Buskens E, Koffijberg H, Algra A |
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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. CRD summary This study assessed the cost-effectiveness of aspirin for the primary prevention of cardiovascular disease events in the Dutch population grouped by age, gender, and level of cardiovascular risk. The authors concluded that aspirin was cost-effective for men 55 years old and over, with twice the general cardiovascular risk, and for older women with higher cardiovascular risk levels. The methods were appropriate and comprehensively reported. Overall, the authors' conclusions appear to be sound. Type of economic evaluation Study objective The aim was to identify the sub-groups of individuals for which low-dose aspirin for the primary prevention of cardiovascular disease events would be cost-effective. Individuals were grouped by their age, gender, and level of cardiovascular risk. Interventions Low-dose aspirin was compared with no aspirin. Individuals were sub-grouped by four ages (45 years, 55 years, 65 years, and 75 years), both genders, and three risk levels (no additional risk, twice the cardiovascular risk, and five times the cardiovascular risk). Location/setting Netherlands/primary prevention. Methods Analytical approach:A Markov model was developed to synthesise both published and unpublished data estimates. The time horizon was 10 years. The authors stated that the perspective was that of the health care payer.
Effectiveness data:The effectiveness data were derived from published literature. A meta-analysis of six randomised controlled trials was the key source of data for clinical efficacy (Berger, et al. 2006, see ‘Other Publications of Related Interest’ below for bibliographic details). The incidence and fatality rates for myocardial infarction, ischaemic stroke, haemorrhagic stroke, and gastrointestinal bleeding were obtained from other published studies. To deal with gaps in the data, several assumptions were made, such as that the relative risks were constant across age groups.
Monetary benefit and utility valuations:The utilities were derived from the literature. In most instances, the preferences were elicited using the time trade-off technique.
Measure of benefit:The measure of benefit was quality-adjusted life-years (QALYs). These were discounted at 1.5% and 4% following Dutch guidelines.
Cost data:The direct medical costs were those of drug treatment, physician visits, and both event-related and ongoing costs such as, hospitalisations, diagnosis, surgery, rehabilitation, and nursing home admissions. Annual costs were presented and these were derived from four Dutch or European published cost studies. Prices were adjusted to 2007 Euros (EUR) using Dutch inflation indexes and costs were discounted at 4%.
Analysis of uncertainty:One-way sensitivity analyses assessed the changes in base results when key parameters were varied. These included the relative risk estimates, drug costs, discount rates, and utilities. The results of a probabilistic sensitivity analysis, with 2,000 Monte Carlo simulations, were presented in the form of cost-effectiveness acceptability curves. Results With no additional cardiovascular risk in 55-year-old men, the life expectancy for the no aspirin group was 9.673 (95% confidence interval, CI: 9.643 to 9.701) compared with 9.687 (95% CI: 9.657 to 9.715) in the aspirin group.
In 55-year-old women, the life expectancy was the same for both groups; no aspirin was 9.798 (95% CI: 9.775 to 9.820) and aspirin was 9.798 (95% CI: 9.775 to 9.821).
The median total costs for aspirin treatment over 10-years for a 55-year-old person were EUR 2,158 for men and EUR 1,471 for women.
The incremental cost per QALY gained for 55-year-old men receiving aspirin treatment was EUR 111,949 with no additional cardiovascular risk and EUR 20,298 with twice the cardiovascular risk. For 55-year old women, with no cardiovascular risk, the costs were higher and the health outcomes poorer for the aspirin group compared with the no aspirin group.
The results were sensitive to the relative risks of disease events, utilities, and cost of aspirin, but stable for different discount rates. The cost-effectiveness ratios were more favourable for older individuals and higher levels of cardiovascular risk. Authors' conclusions The authors concluded that aspirin for the prevention of cardiovascular disease was a cost-effective approach for men and women at certain combinations of age and cardiovascular risk, but less cost-effective for women than men at a similar age. CRD commentary Interventions:The two options and the profile of the intended patient population were clearly described and justified.
Effectiveness/benefits:The effectiveness data were derived from a meta-analysis of six randomised controlled trials (Berger, et al. 2006), which is likely to have provided high quality data. The clinical endpoints incorporated the relevant side-effects of haemorrhagic stroke and gastrointestinal bleeding and full details of their incidence and derivation were reported. The utilities were derived from several published studies, which mainly used the time trade-off technique, which may not be considered the gold standard, but was an appropriate approach. Readers were referred to the sources for further information on the validity of the utilities.
Costs:The costs appeared to reflect those applicable to the health payer perspective. The cost sources and their references were clearly reported, but only the annual costs were given. Readers are referred to the original cost studies for further information on the methods and assessment of their quality.
Analysis and results:An illustration of the model structure was presented and a thorough description of the health states and possible transitions between them was given. The health outcomes and costs were synthesised into incremental cost-utility ratios. All scenarios of age, gender, and cardiovascular disease risk were presented in detail. The parameter uncertainty was addressed through probabilistic sensitivity analyses and the assigned distributions were reported, but no rationale for their selection was discussed. The costs for annual aspirin use, disease events, and complications were not varied in the probabilistic sensitivity analyses. It is unclear why these were omitted and the impact on the findings cannot be assessed. The authors identified and discussed a number of limitations to their study and compared their findings with those from other economic evaluations, which mostly confirmed their conclusions.
Concluding remarks:The methods and limitations were generally reported comprehensively and transparently. The authors’ conclusions appear to be a fair assessment of the analysis undertaken. Funding Supported by a grant from the Netherlands Organization for Health Research and Development (ZonMw). Bibliographic details Greving J P, Buskens E, Koffijberg H, Algra A. Cost-effectiveness of aspirin treatment in the primary prevention of cardiovascular disease events in subgroups based on age, gender, and varying cardiovascular risk. Circulation 2008; 117(22): 2875-2883 Other publications of related interest Berger JS, Roncaglioni MC, Avanzini F, et al. Aspirin for the primary prevention of cardiovascular events in women and men: a sex-specific meta-analysis of randomized controlled trials. JAMA 2006;295:306-13. Indexing Status Subject indexing assigned by NLM MeSH Age Factors; Aged; Aspirin /economics /therapeutic use; Cardiovascular Diseases /epidemiology /prevention & Cost-Benefit Analysis; Drug Evaluation; Female; Humans; Male; Markov Chains; Middle Aged; Monte Carlo Method; Primary Prevention /methods; Risk Assessment; Sex Factors; control AccessionNumber 22008101239 Date bibliographic record published 13/05/2009 Date abstract record published 02/09/2009 |
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