The analysis was based on a decision analytic model and the time horizon was three months. The authors stated that the perspective of the Canadian provincial health care system was adopted.
The clinical evidence came from a review of the literature in commonly used electronic databases. The key inclusion criteria were reported. Randomised controlled trial (RCT) data were supplemented with data from published systematic reviews and meta-analyses. The rates of major bleeding and symptomatic DVT were the key clinical inputs. These were taken from a pivotal RCT (the North American FRAGMIN Trial, NAFT) for total hip replacement patients and from two meta-analyses of RCTs for total knee replacement and hip fracture surgery patients. Some assumptions were also needed.
Monetary benefit and utility valuations:
The utility values were estimated from a random sample of 24 Canadian people using the time trade-off technique.
Measure of benefit:
Quality-adjusted life-years (QALYs) were the summary benefit measure.
The economic analysis included the costs of thromboprophylaxis regimens (supplies, pharmacy mark-up, and dispensing fee), international normalised ratio monitoring, and diagnosis and treatment of clinical DVT and major bleeding events. The analysis covered the time as an in-patient and after discharge. The data sources included a survey of three clinicians from large Canadian hospitals (for the costs associated with DVT episodes), a community pharmacy, the University Health Network in Toronto, various Health Authorities, and other published sources. All costs were in Canadian dollars (CAD) and the price year was 2007.
Analysis of uncertainty:
The issue of uncertainty was investigated in a one-way sensitivity analysis that used ranges of values based on both published sources and expert opinion. An alternative scenario was considered that assumed an additional need for a home-care visit by a nurse, for a proportion of patients on the extended dalteparin regimen. Shorter durations of dalteparin were also considered.