The economic evaluation was conducted alongside a clinical study. The authors stated that the perspective was that of the UK NHS. The time frame was 12 months.
The evidence came from a single randomised controlled trial (RCT). Two hundred and ninety-seven participants were recruited from 55 general practices in Bristol, London and Warwickshire between October 2005 and February 2008. Participants who were on an eight-month waiting list for online CBT were randomly distributed to an online CBT group (149) and a usual care group (148). Clinical outcomes were measured in terms of Beck depression inventory (BDI) score and recovery rate.
Monetary benefit and utility valuations:
The European Quality of life (EQ-5D) instrument was used at baseline and at four and eight months. Results were combined with UK population tariffs to derive quality-adjusted life-years (QALYs) for the health states.
Measure of benefit:
The summary measure of benefit was QALYs.
All health care resources were valued using unit costs derived from nationally available data sources: Health and Social Care 2007, national evaluations, Department of Health reference costs, the British National Formulary, and the Office of National Statistics. All costs were valued in UK pounds sterling (£) at 2007 prices, adjusted for inflation, where necessary. In addition to direct costs, the authors measured and presented productivity costs to enable use of the same analysis from a wider perspective.
Analysis of uncertainty:
Sensitivity analyses was used to investigate the effects of three areas of uncertainty regarding the cost and QALY estimates: the impact of missing data; misreporting of secondary care appointments; and the cost of therapy sessions. Bootstrapping was used to capture the uncertainty around the ratios. A cost-effectiveness acceptability curve was constructed to show the probability of the intervention being cost effective.