Analytical approach:
Two separate Markov models were created to simulate the management of CD with the two interventions, in two cohorts of patients: those with luminal CD and those with fistulising CD. The time horizon of the analysis was 5 years. The authors stated that the perspective of the UK National Health Service (NHS) was adopted.
Effectiveness data:
The clinical data appear to have been derived from a selection of known, relevant studies. The patient characteristics and the treatment effect for infliximab versus standard care were taken from the ACCENT I and II randomised clinical trials (RCTs). Initial response for infliximab was obtained from other published RCTs. Studies reflecting standard treatment protocols, in the authors’ setting, were used to obtain the probability of surgery for those who did not respond to treatment. Some information on the sources of the data was provided. The key clinical estimate was the probability of infliximab maintaining the state of remission.
Monetary benefit and utility valuations:
Utility valuations associated with CD were derived from a study of 200 Spanish patients whose preferences were elicited using the EQ-5D questionnaire and then converted using UK tariffs. Utility valuations relating to surgery and post-surgery health states, were derived from a panel of UK gastroenterologists.
Measure of benefit:
Quality-adjusted life-years (QALYs) were used as the summary benefit measure. QALYs were discounted at an annual rate of 3.5%.
Cost data:
The health services were infliximab (acquisition and administration), concomitant medications, and hospital services (inpatient stay for surgery, diagnostic procedures, examination under anaesthetic, and outpatient visits). The costs of adverse events were not considered. Most of the costs were derived from reference prices published by the NHS. Drug resource use was based on data from the RCTs. Resource consumption of hospital services was derived from published sources. The costs were in UK pounds sterling (£) and referred to the year 2005 to 2006. A 3.5% annual discount rate was applied to future costs.
Analysis of uncertainty:
Deterministic univariate and probabilistic sensitivity analyses were performed to assess how robust the model was in response to variations in key clinical and economic inputs.