Analytical approach:
The analysis was based on a Markov model, with a lifetime horizon and a hypothetical cohort of 10-year-old children with ulcerative colitis. The authors stated that a societal perspective was adopted.
Effectiveness data:
The clinical inputs were identified by a review of electronic databases and clinical trial registries. Studies were selected by their quality (randomised trials were given priority) and their relevance to paediatric ulcerative colitis. Means or medians were calculated to pool evidence from multiple sources. The treatment effects for medical therapy, for VSL#3, and for most escalating therapies were from clinical trials of both children and adults. The efficacy of treatment (response rate while on therapy) was the primary input for the model. Large observational studies were used where clinical trials were not available.
Monetary benefit and utility valuations:
The utility values were from published sources that used the time trade-off and standard gamble methods to elicit preferences for the health conditions associated with ulcerative colitis.
Measure of benefit:
Quality-adjusted life-years (QALYs) were the summary benefit measure and they were discounted at an annual rate of 3%.
Cost data:
The economic analysis included the costs of drugs, hospitalisations, out-patient visits, procedures such as ileal pouch anal anastomosis (IPAA), and laboratory services. The costs of drugs were based on their average wholesale prices, while other medical costs were estimated using national reimbursements from the Centers for Medicare and Medicaid Services or average reimbursement rates from eligible patients at a large medical centre. All costs were in US $ and a 3% annual discount rate was applied. The price year was 2009.
Analysis of uncertainty:
One-way sensitivity analyses were carried out on all the model inputs, using both published and arbitrarily assumed ranges of values.