This economic evaluation used effectiveness and cost data from one randomised controlled trial. The time horizon was four years. The authors stated that the perspective was that of the UK health sector.
The effectiveness data were from the randomised controlled trial of 973 patients. These patients were randomised to warfarin or aspirin treatment and the mean follow-up was 2.7 years. The primary outcomes were fatal (ischaemic) or non-fatal disabling (haemorrhagic) stroke, intracranial haemorrhage, or systemic embolism.
Monetary benefit and utility valuations:
The utility estimates were collected using the European Quality of life (EQ-5D) questionnaire, from the UK general population.
Measure of benefit:
The measure of benefit was the number of quality-adjusted life-years (QALYs), which were discounted at an annual rate of 3.5%.
The cost categories included clinical events, visits to primary care, and visits to the warfarin clinic. The resource data were collected prospectively during the trial, from medical records for primary and secondary care, and death certificates. The clinical events were mapped to UK Healthcare Resource Group codes for non-elective stays and NHS reference costs. The unit costs were provided in 2007 UK pounds sterling (£) and were discounted at an annual rate of 3.5%.
Analysis of uncertainty:
The sensitivity analyses included nonparametric bootstrapping (5,000 repetitions) to account for sampling variation in the estimates of cost-effectiveness. The non-adjustment of QALYs for baseline values on the EQ-5D was assessed, as were shorter follow-up times, and three age subgroups of 75 to 79 years, 80 to 84 years, and 85 years or older.