A model for analyzing the cost of the main clinical events after lung transplantation

Background: The aim of this project was to model clinically important events experienced by lung transplant patients (from the day after transplant to 5 years or death) and costs associated with these events, and to assess the economic impact of different immunosuppression therapies. Methods: The population comprised 356 lung transplant patients (223 heart-lung, 102 single lung and 31 double lung) transplanted between April 1984 and December 1997. AU patients received a cyclosporine-based triple-immunosuppression protocol. We designed a Markov model that included 3 time periods (0 to 6, 7 to 12, and 13 to 60 months), 5 clinical states (well, acute rejection, cytomegalovirus infection, non-cytomegalavirus infection and bronchiolitis obliterans syndrome), and death. For the well state, cost elements were immunosuppression, prophylaxis, and routine clinic visits. For all other states, cost elements were diagnosis, treatment, and bed days/visits. We excluded costs of the procedure. Results: The monthly costs associated with the well state decreased over time, from pound1,778 ($2,658) in the first 6 months to pound 503 ($752) in months 7 to 12 and pound 350 ($523) after the first 12 months. The cost per event of the acute states remained reasonably constant over the 3 periods: pound1,850 ($2,766) for rejection, pound3,380 ($5,053) for cytomegalovirus, and pound2,790 ($4,171) for other infections. The average cost per patient, discounted at 6%, over 5 years was pound 35,429 ($52,966) (95% range, pound1,435 [$2,145] to pound 67,079 [$100,283]). This estimate is most sensitive to changes in immunosuppression. Substituting tacrolimus for cyclosporine increased 5-year costs by 5%; substituting mycophenolate mofetil for azathioprine increased 5-year costs by 26%. Conclusions: This model is valuable in estimating the effect of new immunosuppression agents on the costs of follow-up care.