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A model for assessing the cost-effectiveness of atorvastatin and simvastatin in achieving Canadian low-density lipoprotein cholesterol targets |
Lachaine J, Merikle E, Tarride J E, Montpetit M, Rinfret S |
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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 study compared the cost-effectiveness of two cholesterol-lowering pharmaceuticals, atorvastatin (10 to 80 mg/day) and generic simvastatin (10 to 80 mg/day). Statin medications treat elevated levels of low-density lipoprotein cholesterol (LDL-C), which is an important modifiable risk factor in cardiovascular diseases.
Economic study type Cost-effectiveness analysis.
Study population The study population comprised a hypothetical cohort of dyslipidaemic patients at varying levels of risk for cardiovascular disease who would be eligible for statin treatment.
Setting The setting was outpatient care. The economic study was conducted in Quebec, Canada.
Dates to which data relate Drug acquisition costs related to 2005 Canadian prices. The effectiveness data related to a meta-analysis published in 2003. The dates of the published studies in the meta-analysis were not reported.
Source of effectiveness data The clinical data included medication effectiveness and medication compliance. Medication effectiveness considered the mean expected percentage reduction in LDL-C levels to reach LDL-C target levels. Medication compliance considered the percentage of patients who stopped using the medication.
Modelling An epidemiological model was used to analyse a hypothetical cohort of 1,000 individuals treated with atorvastatin or generic simvastatin over 1 year. The model was well described and illustrated graphically, and all model inputs were clearly justified and their sources stated.
Sources searched to identify primary studies Individuals were assigned baseline LDL-C levels in the standard 0.1 mmol/L categories, based on Canadian population estimates from the Canadian Heart Health Surveys 1986 and 1992. These were translated into low, moderate and high cardiovascular disease risk levels according to Canadian recommendations (Genest et al. 2003, see 'Other Publications of Related Interest' below for bibliographic details). The reductions expected from each statin for each risk level were extrapolated from a meta-analysis (Law et al. 2003, see 'Other Publications of Related Interest' below for bibliographic details). Data relating to medication adherence were obtained from the Quebec provincial drug-reimbursement programme.
Methods used to judge relevance and validity, and for extracting data The authors relied on a systematic review and meta-analysis for the main data on expected reduction in LDL-C levels. No details of the methods used in this review (Law et al. 2003) were provided.
Measure of benefits used in the economic analysis The measure of benefit used was patients treated to the LDL-C target.
Direct costs Drug acquisition costs were the only type of cost included in the analysis. The annual medication cost for each statin was derived from the 2005 Ontario Drug Benefit formulary and it excluded dispensing fees. Discounting was not undertaken, which was appropriate as the analysis covered only a 1-year timeframe. The study reported average costs weighted by the proportion of patients receiving each dose. The daily drug cost and dose were provided.
Statistical analysis of costs The data were deterministic.
Indirect Costs No productivity costs were included in the analysis.
Sensitivity analysis One- and two-way sensitivity analyses were conducted to investigate uncertainty in key parameters. Such parameters included statin effectiveness levels (across upper and lower 95% confidence limits), drug costs from British Columbia, and failure to adhere to statin therapy. Two-way sensitivity analyses of different statin effectiveness levels and drug prices were conducted.
Estimated benefits used in the economic analysis An estimated 735 patients (73%) would be treated to target using atorvastatin compared with 568 patients (57%) using generic simvastatin. Thus, the incremental number of patients treated to target with atorvastatin, compared with generic simvastatin, would be 167 or 16.7% over 1 year.
Results for the sensitivity analyses on different effectiveness parameters did not report the new estimates of benefits separately from the new incremental cost-effectiveness ratios.
Cost results The total drug costs per year were CAD 664,939 for atorvastatin compared with CAD 483,208 for generic simvastatin. Thus, the incremental annual cost was CAD 181,731 for atorvastatin compared with generic simvastatin.
Synthesis of costs and benefits The annual cost per additional patient treated to target was CAD 1,088.
Sensitivity analyses showed lower incremental cost-effectiveness ratios of CAD 872 when the upper 95% confidence interval (CI) level of effectiveness was used, and CAD 1,314 when the lower 95% CI was used (changes of 20%).
When the upper 95% CI level of effectiveness was used simultaneously with the higher drug costs from British Columbia, the incremental cost-effectiveness ratio was CAD 738 (-32% change).
Minor changes in the base ratio occurred with the integration of expected drug adherence rates.
Authors' conclusions The authors stated that their model predicted better health outcomes for patients treated with atorvastatin compared with generic simvastatin, and that this was achieved at an extra cost of CAD 1,088 per patient treated to target.
CRD COMMENTARY - Selection of comparators Two common statin drugs making up a substantial proportion of the market share in Canada were compared, and the authors provided an adequate justification for their choice. You should decide if these represent widely used statin drugs in your own setting.
Validity of estimate of measure of effectiveness The clinical data estimates were derived from a systematic review and meta-analysis of the published literature (Law et al. 2003). Potentially, this represents the highest quality of evidence for use in modelling analyses. However, the reader would need to assess the methods and quality of the meta-analysis by reference to the original paper (Law et al. 2003), as the authors did not provide any information about the meta-analysis methods. In addition, the study was published 4 years before the present study and, therefore, might not have included relevant studies published between 2003 and 2007. Validity of estimate of measure of benefit The authors adopted an intermediate clinical outcome, namely patients treated to target. While this is clinically relevant, this measure does not capture longer term health benefits such as the commonly used generic outcome measure quality-adjusted life-years gained or life-years gained. Unlike several previous studies, the authors also chose not to use reduced acute cardiovascular events. These factors mean that it is difficult to compare the results of this study with those from other studies of statin drugs, or other health care technologies that have used these final outcome measures or that extended beyond a short 1-year time horizon.
Validity of estimate of costs All the relevant costs from the perspective of the Canadian government payer appear to have been included in the analysis. Discounting was unnecessary given the short timeframe of the analysis (1 year). The resource units and costs were taken from public pharmaceutical listings. The costs and quantities were adequately and clearly presented in the report.
Other issues The authors compared their results with those from other studies and discussed, in detail, the differences they found in several studies originating in Canada and various other countries. The authors discussed issues around generalisability, that is, different LDL-C distributions among other populations, different national LDL-C targets, different drug prices and clinical practice. The analysis involved a hypothetical cohort of ideal candidates for statin therapy. However, it was unclear how the results would alter if patient circumstances changed as they do in real life (e.g. adverse medication effects, contraindications, co-morbid diseases). The authors noted some limitations to their analysis and do not appear to have presented their results selectively.
Implications of the study The model presented in this study predicts that a higher number of patients treated to target will be achieved when using atorvastatin rather than generic simvastatin, at an additional cost of CAD 1,088 per patient over a 1-year period. Further research to assess the longer term health benefits of atorvastatin, compared with generic simvastatin, is warranted. The research should also incorporate more complex sensitivity analyses and should reflect actual clinical practice parameters.
Source of funding Supported by BioMedCom Consultants Inc.
Bibliographic details Lachaine J, Merikle E, Tarride J E, Montpetit M, Rinfret S. A model for assessing the cost-effectiveness of atorvastatin and simvastatin in achieving Canadian low-density lipoprotein cholesterol targets. Clinical Therapeutics 2007; 29(3): 519-528 Other publications of related interest Because readers are likely to encounter and assess individual publications, NHS EED abstracts reflect the original publication as it is written, as a stand-alone paper. Where NHS EED abstractors are able to identify positively that a publication is significantly linked to or informed by other publications, these will be referenced in the text of the abstract and their bibliographic details recorded here for information.
Genest J, Frohlich J, Fodor G, McPherson R. Recommendations for the management of dyslipidemia and the prevention of cardiovascular disease: summary of the 2003 update (published correction appears in CMAJ 2003;169:1149). CMAJ 2003;169:921-4.
Law MR, Wald NJ, Rudnicka AR. Quantifying effect of statins of low density lipoprotein cholesterol, ischaemic heart disease, and stroke: systematic review and meta-analysis. BMJ 2003;326:1423.
Indexing Status Subject indexing assigned by NLM MeSH Atorvastatin Calcium; Canada; Cholesterol, LDL /blood; Cost-Benefit Analysis; Drug Costs; Dyslipidemias /drug therapy /economics; Heptanoic Acids /economics /therapeutic use; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors /economics /therapeutic use; Models, Economic; Pyrroles /economics /therapeutic use; Simvastatin /economics /therapeutic use AccessionNumber 22007008124 Date bibliographic record published 30/11/2007 Date abstract record published 30/11/2007 |
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