The analysis was based on a decision tree that used data from a clinical trial. The time horizon was 90 days and the authors stated that the perspective of the hospital was adopted.
The clinical data on the efficacy and safety of the two treatments were from a published open-label, randomised controlled trial; the Prevention of Venous Thromboembolism After Acute Ischemic Stroke with Low-Molecular-Weight Heparin and Unfractionated Heparin (PREVAIL) trial (Sherman, et al. 2007, see 'Other Publications of Related Interest' below for bibliographic details). The number of venous thromboembolisms, including deep vein thrombosis (DVT) and pulmonary embolism, was the primary endpoint of the analysis.
Monetary benefit and utility valuations:
Measure of benefit:
No summary benefit measure was used. The rates of venous thromboembolism and pulmonary embolism were the main outcomes of the analysis.
The economic analysis included the costs of prophylaxis and the treatment of venous thromboembolisms. The drug costs were estimated, using their average wholesale prices and the dosages used in the PREVAIL trial. An administration fee was added for each dose. The costs of clinical events were estimated using a multivariate cost-evaluation model, based on the mean hospital costs from a database of over 600 hospitals representing all geographical areas of the USA. All costs were in US $ and the price year was 2008.
Analysis of uncertainty:
Subgroup analyses were carried out by severity of stroke, measured on the National Institutes of Health Stroke Scale (NIHSS); less severe was a score of less than 14, and more severe was 14 or more. Sensitivity analyses were performed to examine the impact of variations in the cost inputs and the clinical event rates, on the total costs. Alternative values for the inputs were defined by the authors. In a Monte Carlo simulation, all the parameters were simultaneously varied within beta distributions for the clinical events and gamma distributions for the costs.