Analytical approach:
A fixed time increment, stochastic model, with a one-week cycle length, was developed to estimate the cost-effectiveness of the two interventions. A five-year time horizon was used, and the authors stated that the perspective of the UK NHS was adopted.
Effectiveness data:
The clinical data were from a systematic review of the literature. Initially, randomised controlled trials (RCTs) were sought, but none was found. Subsequently, a search of PubMed and the Internet, using Google, with the search terms 'pregabalin' and 'refractory', identified four relevant, prospective, non-randomised studies. Authors’ assumptions were used to generate estimates for missing data, in the four studies. The main measure of effectiveness was the reduction in pain score.
Monetary benefit and utility valuations:
The utility estimates were from 284 pain clinic out-patients with both refractory and non-refractory neuropathic pain, who completed the European Quality of life (EQ-5D) questionnaire and a pain scale. A mapping function was used to convert the pain scores to EQ-5D scores and estimate utility. The utility values for adverse events were assumed by the authors.
Measure of benefit:
The main measure of benefit was quality-adjusted life-years (QALYs), which were discounted at an annual rate of 3.5%.
Cost data:
The economic analysis considered drug acquisition and NHS and Personal Social Services expenditure. The resource use data were from the survey that provided the utility values and the drug costs were from the British National Formulary. Other cost estimates were mainly from the Personal Social Services Research Unit, with some author assumptions. The costs were discounted at an annual rate of 3.5% and all costs were reported in £.
Analysis of uncertainty:
The analysis of uncertainty included a number of deterministic one-way sensitivity analyses, varying the cost of usual care, the frequency of adverse events, and the time horizon.