The decision model had a lifetime horizon. A decision tree simulated patient management for the 112 days of prophylaxis, and a Markov model, with one-month cycles, simulated their remaining lifetime. The authors stated that the perspective of the US payer was adopted.
Most of the evidence was from a published multinational, randomised, double-blind, clinical trial of transplant recipients with grades two to four acute graft-versus-host disease, or extensive and chronic graft-versus-host disease, who were receiving intensive immunosuppression. This head-to-head trial provided data for the treatment effect and the patients’ characteristics. Survival beyond the 16-week trial was estimated using published information and authors’ assumptions. The efficacy of prophylaxis in preventing invasive fungal infection was the primary endpoint of the analysis.
Monetary benefit and utility valuations:
Measure of benefit:
Life-years saved and invasive fungal infections avoided were the summary benefit measures. A 3% annual discount rate was used.
The economic analysis included the costs of antifungal prophylaxis and infection treatment. Prophylaxis was based on average prices for generic drugs. Treatment costs were from the Nationwide Inpatient Sample. Any charges were converted to costs using hospital-specific cost-to-charge ratios. All costs were in US $. The price year was 2006 and a 3% annual discount rate was applied.
Analysis of uncertainty:
Several one-way sensitivity analyses were carried out to assess the uncertainty around the key inputs for the model, using ranges mainly based on published confidence intervals or authors’ assumptions. A second-order probabilistic Monte Carlo simulation was performed, focusing on the key inputs, such as the probability of infection, the probability of death due to infection, the probability of death from other causes, and the treatment cost; conventional distributions were used.