Analytical approach:
The analysis was based on a Markov model, with a one-year time horizon and a hypothetical cohort of 100,000 male patients, with a mean age of 65 years, a smoking history of at least 50 pack-years (one pack-year defined as one packet per day for a year or the equivalent total over time), and a disease duration of at least 9.5 years. The authors stated that the analysis was conducted from the perspective of the third-party payer.
Effectiveness data:
A literature search was undertaken to identify the relevant clinical trials for the efficacy of the study drugs. Four placebo-controlled, randomised clinical trials were included, one of which provided head-to-head data for salmeterol versus tiotropium. The data for no treatment were from the placebo arms of the clinical trials. Other published studies were used for patients’ compliance. The key input for the model was the efficacy rate.
Monetary benefit and utility valuations:
Not considered.
Measure of benefit:
The number of exacerbations (severe or not) was the benefit measure.
Cost data:
The economic analysis included the costs of drugs, hospitalisations, monitoring (laboratory tests), and physician visits. Conventional patterns of resource consumption were assumed. The drug costs and cost of maintenance therapy were based on average wholesale prices. All other costs were from Medicare sources. The costs were in US dollars ($) and the price year was 2006.
Analysis of uncertainty:
The uncertainty was investigated in a first-order Monte Carlo simulation, which assessed the variability around the mean outputs. A one-way sensitivity analysis focused on the following parameters: the probability of exacerbation, the probability of hospitalisation, the probability of severe exacerbation, and the compliance rate. The ranges of values were from the literature or were assumed to be ±20% of the baseline value.