Analytical approach:
A decision tree was used to compare the impact of treatment on patients' transition along the clinical pathway. The time horizon of the study was patients' lifetime. The authors stated that the perspective taken was that of the health care system.
Effectiveness data:
The main effectiveness data came from a large placebo controlled trial (3,000 participants) of prophylactic fondaparinux followed for 45 days. The clinical outcomes included: the probabilities of complications including major haemorrhage; venous thromboembolism; pulmonary embolism; deep vein thrombosis; extension to the saphenofemoral junction(with and without treatment); and recurrently superficial vein thrombosis (with and without treatment). These data were combined with other estimates (case-fatality of pulmonary embolism and haemorrhagic complications) from the published literature, which primarily came from a meta-analysis of thromboprophylaxis in medical patients.
Monetary benefit and utility valuations:
Utility data were reported to have been derived from the published literature and expert opinion of two of the authors.
Measure of benefit:
The primary measure of benefit was quality-adjusted life-years (QALYs), which were used to estimate cost per QALY gained. Future benefits were discounted at a rate of 3% per year.
Cost data:
The cost categories included were the costs of drugs, hospitalisations, visits to physicians, and medical procedures. The source of hospital, physician, lab tests and medical procedure prices were Medicare reimbursement schedules; fondaparinux drug costs were from wholesale acquisition cost and warfarin cost as a decrease of 15% on average wholesale costs. All costs were adjusted to 2010 US £ using the medical care component of the consumer price index. Future costs were discounted at a rate of 3% per year.
Analysis of uncertainty:
One-way and probabilistic sensitivity analyses were conducted. In addition, scenario analysis based on a shorter duration of treatment was also undertaken. The results were presented in tornado diagrams and cost-effectiveness acceptability curves.