Analytical approach:
The economic evaluation was based on a Markov model with a lifetime horizon. The authors stated that the analysis was conducted from the perspective of the payer (the UK Department of Health).
Effectiveness data:
The bulk of the clinical evidence came from the INFORCE study, a multicentre, multi-country, randomised, controlled trial (RCT) with a 12-week time horizon and a sample of 384 patients who had received a suboptimal statin dose and who were either switched to ezetimibe/simvastatin or had their statin dose doubled. The primary endpoint was the reduction in lipid levels with these two options. These data were used in the Markov model to project the long-term risk of coronary heart disease (CHD), using Framingham risk equations. The death rates not related to ACS, were from the UK Office for National Statistics.
Monetary benefit and utility valuations:
The utility values were from a published pharmacoeconomic model.
Measure of benefit:
Quality-adjusted life-years (QALYs) were the summary benefit measure and they were discounted at an annual rate of 3.5%.
Cost data:
The economic analysis included the costs of prescriptions for statins and ezetimibe and the annual event costs associated with non-fatal myocardial infarction, stable angina pectoris, unstable angina, and fatal CHD. The drug costs were from the Department of Health, while the disease-related costs were from two previous economic evaluations. All costs were in UK pounds sterling (£) and a 3.5% annual discount rate was applied. The price year was 2008 for cardiovascular disease costs and 2009 for other costs.
Analysis of uncertainty:
A statistical analysis was undertaken to account for baseline differences between the treatment groups in the clinical trial. Bootstrapping was also carried out for the expected total costs, QALYs, and incremental cost-utility ratios. A sensitivity analysis was conducted on the projected costs and benefits, assuming that the acquisition price for generic atorvastatin was equivalent to that for generic simvastatin.