Analytical approach:
A published decision-tree model (Berg, et al. 2007, see 'Other Publications of Related Interest' below for bibliographic details) was adapted, using Swedish and German data, to assess the lifetime costs and effects of the two interventions in the Netherlands. The time horizon was when the patients reached the age of 100 years and the authors reported that a societal perspective was adopted.
Effectiveness data:
The clinical and effectiveness data were from published studies. Swedish hospital discharge and death registers were used for the risk of events. The main effectiveness estimate was the combined endpoint of an occluded infarct-related artery, a recurrent myocardial infarction (MI) before angiography, or death. Effectiveness data were derived from the Clopidogrel as Adjunctive Reperfusion Therapy (CLARITY) trial (Sabatine, et al. 2005, see 'Other Publications of Related Interest' below for bibliographic details). The CLARITY trial was a randomised, double-blind, placebo-controlled trial of 3,491 patients.
Monetary benefit and utility valuations:
The utilities were derived from a Swedish study that evaluated utility in a population with moderate-to-severe health problems, which were comparable to those of STEMI patients.
Measure of benefit:
Life-years gained and quality-adjusted life-years (QALYs) gained were the measures of benefit and they were discounted at an annual rate of 1.5%, according to Dutch guidelines.
Cost data:
The authors reported that both the direct and indirect costs were included. These included the costs of MI, stroke, gastrointestinal bleeding, and subsequent events. The additional costs of clopidogrel were also analysed, but the costs of aspirin were omitted, as they were a part of both regimens. The clopidogrel costs were from pharmacists’ prescriptions and all other costs were from fee schedules and published literature. The indirect costs were adjusted, using the friction cost method, to take into account compensation by the remaining labour force. All costs were reported in Euros (EUR) and the price year was 2006. Future costs were discounted at an annual rate of 4%, in accordance with Dutch guidelines.
Analysis of uncertainty:
A series of one-way sensitivity analyses was undertaken to evaluate the impact of varying the efficacy rates, discount factors, and costs. A multivariate probabilistic sensitivity analysis was undertaken by applying probability distributions to all the model parameters and then using a Monte Carlo simulation. The results were presented as incremental cost-effectiveness scatter plots and acceptability curves.