Analytical approach:
This economic evaluation was based on a decision analytic model with a three-month time horizon. The authors stated that the analysis was carried out from the perspective of the British National Health Service (NHS).
Effectiveness data:
The clinical data came from an administrative database, namely The Health Independent Network (THIN) database, which contained long-term medical records representative of the entire UK population. The procedure to identify patients was described and there were 977 patients in each of the two treatment groups. They were well matched in terms of age, gender and the time between starting the new treatment and the previous laxative. The key clinical endpoint was the proportions of patients remaining on their laxative, discontinuing treatment, or switching to another laxative.
Monetary benefit and utility valuations:
The utility estimates were derived from a previous study that examined a sample of 308 members of the general public across the UK, using the standard gamble and time trade-off methods.
Measure of benefit:
The two summary benefit measures were the proportion of patients successfully treated over three months and quality-adjusted life-years (QALYs).
Cost data:
The health service costs were those of the two drugs, accident and emergency attendances, general practitioner (GP) visits (at home and in the clinic), GP telephone consultations, hospital out-patient visits, laboratory tests, and practice nurse visits. The resource use data were derived from the THIN database. The unit costs and quantities of resources used were presented for all items. These costs were derived from the Drug Tariff, the British National Formulary, NHS Reference Costs, and the Personal Social Services Research Unit. All costs were in UK pounds sterling (£) and referred to 2004 to 2005 prices.
Analysis of uncertainty:
A probabilistic sensitivity analysis was undertaken by assigning probability distributions to all the model inputs. A deterministic sensitivity analysis was also carried out on the key inputs.