Analytical approach:
The analysis was based on a Markov model, with a one-year time horizon. The authors stated that a societal perspective was adopted.
Effectiveness data:
The clinical evidence came from selected studies that included three published clinical trials. One of these was a six-week randomised sham-controlled trial, with a sample of 301 patients, and two studies were open-label extensions of this trial, with a maximum of 24 weeks of follow-up. The key input to the model was the treatment efficacy, which was defined as the difference in the Montgomery and Asberg Depression Rating Scale (MADRS) score, between sham and active treatment, in week four of the acute treatment phase. The data for pharmacological treatment were from the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) trial of 1,669 patients with major depression.
Monetary benefit and utility valuations:
The utility values were from two published sources, one of which was a report completed for the National Institute for Clinical Excellence (NICE) in 2002.
Measure of benefit:
Quality-adjusted life-years (QALYs) were the summary benefit measure.
Cost data:
The three main cost categories were health care use (TMS, treatment of depression, hospitalisations, emergency department visits, primary care visits, and antidepressant therapy), caregiver support, and productivity lost. The resource use data were from the clinical trials and were collected using specific self-report questionnaires. The costs were from large national databases of Medicaid billing data for patients with depression and they were adjusted by disease severity. They were in US dollars ($) and the price year was 2006.
Analysis of uncertainty:
The impact of variations in the clinical assumptions, cost weights, and quality-of-life adjustments was considered in a deterministic sensitivity analysis, using published and arbitrary ranges of values. The sensitivity analysis also considered the exclusion of indirect costs, variations in the cost of a suicide attempt, or both. A subgroup analysis considered patients who had failed to receive clinical benefit from only one pharmacological treatment.