A Markov model was constructed to extrapolate the clinical outcomes, costs and effects over a patient's lifetime. The model was based on one used in a previous study and the time horizon was 50 years. The authors reported that the perspective was that of the Dutch health care system.
The effectiveness data for the two populations were obtained from two separate studies, namely the Percutaneous Coronary Intervention - Clopidogrel in Unstable Angina to Prevent Recurrent Events (PCI-CURE) and the Clopidogrel for the Reduction of Events During Observation (CREDO) studies, which were augmented with data from the relevant literature. The individual event probabilities for the first year were estimated using event-specific Weibull models. The subsequent event probabilities were based on the data from the second half of the year and adjusted for higher risk, using relative rates. The main clinical parameters included the risk of events such as fatal and non-fatal Myocardial infarction (MI) and stroke, coronary artery bypass graft (CABG), PCI, and cardiovascular death.
Monetary benefit and utility valuations:
The utility values for the different health states, were obtained from the literature and were fully presented.
Measure of benefit:
Life-years gained and quality-adjusted life-years (QALYs) were the measures of benefit and they were discounted at an annual rate of 4%.
The cost categories included those of acute care, drugs, PCI, CABG, and the treatment of events such as major bleeding or MI in the first six months or one year. The summary costs were reported for each event and these were derived from published studies and a national price publication. All costs were in Euros (EUR), for the price year 2004, and adjusted for inflation using price indices. They were discounted at an annual rate of 4%.
Analysis of uncertainty:
The parameter uncertainty was investigated using one-way sensitivity analyses on all the cost estimates, various clinical effectiveness parameters, and the utility values. The ranges over which the parameters were tested were reported. In addition, probabilistic sensitivity analysis was conducted, using Monte Carlo simulations, and the parameter distributions were clearly described.