A state transition model of the ongoing risk of death, from several diseases, was used. The intervention changed the probabilities of having each disease. The time horizon was the patient's lifetime and treatment was received for 15 years. The authors reported that a societal perspective was adopted.
The effectiveness data were mainly derived from published observational studies or randomised trials. The primary clinical outcomes were the relative risks, with or without therapy, of diseases, such as breast cancer, pulmonary embolism, cardiovascular events, colon cancer, and hip fracture.
Monetary benefit and utility valuations:
The utility scores for each health state were a combination of an age-adjusted utility score, a disease-state utility score, and the relative utility for hormone therapy. All the utilities were from published sources.
Measure of benefit:
Quality-adjusted life-years (QALYs) were the summary measure of benefit and they were discounted at an annual rate of 3%.
The economic analysis included the cost of cardiovascular events, hip and vertebra fractures, breast and colon cancer, pulmonary embolism, and hormone therapy. The annual summary costs were reported for each category. These were from various published studies. Average wholesale prices were used for the medication costs, and these were from official national sources. All costs were adjusted for inflation and were reported in US dollars ($) for the price year 2006. They were discounted at an annual rate of 3%.
Analysis of uncertainty:
The parameter uncertainty was investigated in a probabilistic sensitivity analysis, using Monte Carlo simulations. A deterministic one-way sensitivity analysis was also used on all the model parameters. A worst-case scenario, where therapy had its least benefit, highest cost, and most risk, was also tested. The treatment duration was varied, from five to 30 years for the younger cohort and five to 15 years for the older cohort, and the use of oestrogen only was also tested.