Analytical approach:
A Markov model was used to determine the clinical and economic outcomes for the two interventions. The time horizon of the study was 10 years. The authors reported the perspective to be that of the National Health Service in England and Wales.
Effectiveness data:
Many of the transition probabilities used in the model were derived from the ACT I and ACT II trials - two known, randomised controlled trials which investigated the efficacy of IFX SMT. Other effectiveness data were derived from the published literature. The primary outcome measure was the health state of the patient at the end of the follow-up period, which included remission, mild UC, moderate to severe UC, and surgery.
Monetary benefit and utility valuations:
Most of the utility valuations were obtained from a previous study of UC patients carried out in a Cardiff hospital using the EuroQol at five dimensions (EQ-5D) and valued using UK tariffs. The utilities which were not available from that study were obtained from an alternative published study.
Measure of benefit:
Quality-adjusted life-years (QALYs) were the summary benefit measure and they were discounted at an annual rate of 3.5%.
Cost data:
The direct medical costs included those associated with IFX SMT, other drug costs, adverse events and surgery, hospitalisation, and other assessments. The cost data were generally obtained from published studies, while the resource use data were derived from the ACT trials. The authors reported that no published estimates were available for the resource use for health care related to UC, for patients in pre-surgery health states, and so these data were estimated by a panel of six UK gastroenterologists. The price year was 2006 to 2007 and all costs were reported in UK pounds sterling (£). They were discounted at an annual rate of 3.5%.
Analysis of uncertainty:
Multiple one-way sensitivity analyses were performed on a number of model inputs including patient age, weight, the time horizon of the study, and the discount rate. Important model inputs, including the transition probabilities and health state utilities, were examined in a probabilistic sensitivity analysis with 10,000 simulations.