Analytical approach:
The analysis was based on a single study and the time horizon was 30 days. The authors stated that the perspective of the NHS was adopted.
Effectiveness data:
The clinical data were from the published General Anaesthetic versus Local Anaesthetic for carotid surgery (GALA) trial (GALA Trial Collaborative Group, et al. 2009, see ‘Other Publications of Related Interest’ below for bibliographic details). This was an international randomised trial that was carried out in 95 centres in 24 countries. There were 3,526 participants, with 1,753 receiving general anaesthesia and 1,773 receiving local. The analysis was based on the intention-to-treat principle. The length of follow-up was 30 days after surgery. The key outcome was the time free from any event, such as stroke (including retinal infarction), myocardial infarction, or death, during the 30 days of follow-up.
Monetary benefit and utility valuations:
Not considered.
Measure of benefit:
The benefit measure was the time free from any event and this was derived directly from the clinical trial.
Cost data:
The economic analysis considered the in-patient costs for surgery (theatre and staff), hospital stay, consumables and drugs, and treatment of complications. The resource use data were gathered during hospital stay in the clinical trial. Further data on staff time were from a retrospective survey sent to the 17 UK centres that participated in the GALA trial. The unit costs were reported and were from official NHS sources, such as the Personal Social Services Research Unit, the Department of Health, and the British National Formulary. The costs of shunts and patches were from their manufacturers. All costs were in UK pounds sterling (£) and referred to 2003 to 2004 prices.
Analysis of uncertainty:
The correlation between costs and health outcomes was accounted for using a system of seemingly unrelated regressions. Cost-effectiveness acceptability curves were calculated for various willingness-to-pay thresholds. In an alternative scenario, the clinical and economic outcomes were assessed over a one-year period. Three subgroup analyses were carried out for: patients with a contralateral carotid occlusion; patients aged over 75 years; and patients with a high, medium, or low baseline risk of an adverse outcome.