A Markov decision model was used to assess the costs and outcomes of the two options. The time horizon was 20 years. The authors reported that a societal perspective was adopted.
The clinical and effectiveness data were from published studies. The main measure of effectiveness was the probability of adverse events, such as ischaemic stroke, intracranial haemorrhage, myocardial infarction, and death. These estimates were from a sub-study of the Randomised Evaluation of Long-Term Anticoagulation Therapy (RE-LY) trial of dabigatran and warfarin in secondary stroke prevention, and other trials of warfarin therapy for atrial fibrillation.
Monetary benefit and utility valuations:
The utility estimates for no disability on different drugs, and for the adverse events, were from published studies. There were no data available on the utility for patients on dabigatran, so it was assumed to be the same as that of patients on ximelagatran, an older thrombin inhibitor.
Measure of benefit:
The measure of benefit was quality-adjusted life-years (QALYs) gained. As benefits could be generated over 20 years, future benefits were discounted at an annual rate of 3%.
The direct costs were those of dabigatran, office doctor visits, warfarin, anticoagulation management, international normalised ratio tests, hospitalisations for adverse events, and ongoing medical care for adverse events. The costs of dabigatran were based on its wholesale price. The costs of doctor visits, tests and management were from Medicare reimbursements. Hospitalisation costs were from the Healthcare Cost and Utilization Project. The price year was 2010 and costs were discounted at an annual rate of 3%. All costs were reported in US $.
Analysis of uncertainty:
One-way sensitivity analyses were performed by varying all the model inputs over plausible ranges of values. A probabilistic sensitivity analysis was undertaken, using Monte Carlo simulation, with 10,000 iterations.