Analytical approach:
The effectiveness and resource use data were derived from a randomised controlled trial. The study protocol determined that, if no statistically significant difference was found in the debridement time between loose and bagged larvae, these two groups would be combined. As a result, the economic analysis compared hydrogel with larvae. The time horizon of the analysis was 12 months. The authors reported that the perspective adopted was that of the National Health Service (NHS).
Effectiveness data:
The effectiveness data were derived from a single randomised controlled trial, the leg ulcer trial VenUS II, the details of which were published elsewhere (Dumville, et al. 2009, see 'Other Publications of Related Interest' below for bibliographic details). A total of 267 patients were recruited into the trial with 94 allocated to loose larvae, 86 to bagged larvae, and 87 to hydrogel. The randomised treatments were administered to 88 (94%) loose larvae, 82 (95%) bagged larvae, and 78 (90%) hydrogel patients. The mean follow-up time was 167 days for the loose larvae, 170 days for the bagged larvae, and 175 days for the hydrogel group. The main clinical estimate in the effectiveness study was the mean time to healing.
Monetary benefit and utility valuations:
The quality of life was derived from the European Quality of life (EQ-5D) questionnaire, which was administered to patients at baseline and at three, six, nine, and 12 months. The utility scores were calculated using societal preferences elicited from a random population sample, using a time trade-off technique.
Measure of benefit:
The measures of benefit were quality-adjusted life-years (QALYs) and the mean time to healing.
Cost data:
The direct costs were those relating to: bagged and loose larvae; hydrogel applications; nurse and doctor visits at home, clinics and hospital; and compression therapy. The resource use data were derived from nurse-completed and participant-completed questionnaires. The unit costs for debriding agents were derived from the British National Formulary. The unit costs for other items were derived from a compendium of unit costs of health care in the UK. The price year was 2006 and all costs were reported in UK pounds sterling (£).
Analysis of uncertainty:
The 95% confidence intervals (CIs) for the differences in costs and effectiveness were calculated using non-parametric bootstrap estimates. The uncertainty surrounding the incremental cost-effectiveness and incremental cost-effectiveness ratios was evaluated, using cost-effectiveness acceptability curves. A series of one-way sensitivity analyses were also performed by varying the unit costs and the duration of debridement.