Analytical approach:
The analysis was based on a decision-tree model, of a hypothetical 59-year-old haemodynamically stable woman, followed by a Markov node to model radiation-induced carcinogenesis. A lifetime horizon was considered. The authors stated that a societal perspective was adopted.
Effectiveness data:
The clinical data were from a selection of relevant studies. The authors selected the most appropriate estimate from the available evidence. The key input was the sensitivity and specificity of both CT angiogram for pulmonary embolism and compression ultrasonography for DVT.
Monetary benefit and utility valuations:
The utility values were from published sources.
Measure of benefit:
Quality-adjusted life-years (QALYs) were the summary benefit measure and they were discounted at an annual rate of 3%.
Cost data:
The economic analysis included the costs of hospital stay, professional services, imaging studies, anticoagulation therapy, and out-patient follow-up (physician office visits, anticoagulation clinic visits for fingerprick international normalised ratio checks, and warfarin). The long-term costs of complications, treatment of cancer, and death were considered. The resource quantities were based on published reports and authors’ opinions. The costs were from Medicare and the National Physician Fee Schedule for out-patient treatment. They were in US dollars ($) and the price year was 2009.
Analysis of uncertainty:
All the model inputs were varied in a one-way sensitivity analysis, using plausible ranges of values from published studies.