Analytical approach:
The analysis was based on a decision-analytic model of the costs and benefits, for the first year, with a Markov model, for the lifetime horizon. The authors stated that the analysis was carried out from the perspective of the UK NHS.
Effectiveness data:
The clinical evidence came mainly from two sources; the Acute Catheterization and Urgent Intervention Triage Strategy (ACUITY) trial and the Global Registry of Acute Coronary Events (GRACE). The treatment effect for bivalirudin and heparin plus glycoprotein IIb/IIIa inhibitor and the consequent event rates, which were the key inputs for the model, were from the ACUITY trial, which was a large, multicentre, prospective, randomised, open-label, parallel-group, phase III trial. Additional data for heparin plus glycoprotein IIb/IIIa inhibitor were from UK patients in the GRACE, which was a large-scale, multinational, observational study of acute coronary syndrome patients recruited from 1999 to 2007. Patients with similar characteristics in the ACUITY trial and the GRACE were considered. The two analyses were carried out separately. Additional calculations for long-term survival were based on the Nottingham Heart Attack Register.
Monetary benefit and utility valuations:
The utility values were from a study of 229 consecutive myocardial infarction survivors, from a UK centre. The European Quality of Life (EQ-5D) instrument was used, with UK tariffs derived using the time trade-off method.
Measure of benefit:
Quality-adjusted life-years (QALYs) were the summary benefit measure and were discounted at an annual rate of 3.5%.
Cost data:
The economic analysis included the drugs, hospitalisations, events and procedures (angiography, coronary artery bypass graft, and percutaneous coronary interventions), and long-term annual cardiovascular treatment for one-year survivors. The resource use data were from the two main clinical sources, wherever possible. The costs were from UK sources, such as NHS reference costs and the British National Formulary. They were in UK pounds sterling (£) and referred to 2007 to 2008 prices. A 3.5% annual discount rate was applied.
Analysis of uncertainty:
A deterministic sensitivity analysis was undertaken on the major inputs for the model, using published confidence intervals for the clinical inputs, interquartile ranges for the costs, and ±25% for the survival and utility scores. A probabilistic analysis was carried out, considering conventional distributions of probability for the model inputs. Several alternative scenarios, reflecting UK medical practice, were considered.