Economic Evaluation of Extending Medicare Immunosuppressive Drug Coverage for Kidney Transplant Recipients in the Current Era

Abstract

Background: Kidney transplant recipients must take immunosuppressant drugs to prevent rejection and maintain transplant function. Medicare coverage of immunosuppressant drugs for kidney transplant recipients ceases 36 months after transplantation, potentially increasing the risk of transplant failure. A contemporary economic analysis of extending Medicare coverage for the duration of transplant survival using current costs of immunosuppressant medications in the era of generic equivalents may inform immunosuppressant drug policy.

Methods: A Markov model was used to determine the incremental cost and effectiveness of extending Medicare coverage for immunosuppressive drugs over the duration of transplant survival, compared with the current policy of 36-month coverage, from the perspective of the Medicare payer. The expected improvement in transplant survival by extending immunosuppressive drug coverage was estimated from a cohort of privately insured transplant recipients who receive lifelong immunosuppressant drug coverage compared with a cohort of Medicare-insured transplant recipients, using multivariable survival analysis.

Results: Extension of immunosuppression Medicare coverage for kidney transplant recipients led to lower costs of -$3077 and 0.37 additional quality-adjusted life years (QALYs) per patient. When the improvement in transplant survival associated with extending immunosuppressant coverage was reduced to 50% of that observed in privately insured patients, the strategy of extending drug coverage had an incremental cost-utility ratio of $51,694 per QALY gained. In a threshold analysis, the extension of immunosuppression coverage was cost-effective at a willingness-to-pay threshold of $100,000, $50,000, and $0 per QALY if it results in a decrease in risk of transplant failure of 5.5%, 7.8%, and 13.3%, respectively.

Conclusions: Extending immunosuppressive drug coverage under Medicare from the current 36 months to the duration of transplant survival will result in better patient outcomes and cost-savings, and remains cost-effective if only a fraction of anticipated benefit is realized.

Keywords: Economic Analysis; Medicare; kidney transplantation; transplant outcomes.

Figure 1.

Health states and transitions in the Markov model.

Figure 2.

Cohort used in survival analysis to establish transition probabilities. The final analytic cohort included 94,667 patients.

Figure 3.

State probabilities from multistate survival model adjusting for age, sex, race, cause of ESKD, history of prior kidney transplant, and type of kidney transplant stratified by insurance status. Health states presented in this figure include alive with function, failed transplant, and death with function. Individuals in the failed transplant group include those who are alive and those who have died after transplant failure.

Figure 4.

State probabilities of patients with a failed kidney transplant from multistate model. Only state probabilities for Medicare-insured individuals are reported in this diagram. Health states presented in this figure include alive with a failed transplant, retransplantation, and death after transplant failure.

Figure 5.

The cumulative cost and cost-effectiveness of extending immunosuppressive drug coverage for the duration of transplant survival compared with the current Medicare policy in which drug coverage ceases at 36 months. In this plot, the results of the primary model and the sensitivity analyses where only 75% and 50% of this potential reduction in graft loss with extension of Medicare immunosuppression coverage were realized. The ICUR for each scenario is plotted. The scenario where the estimated benefit was realized dominated the current policy, meaning it was less costly with more effectiveness over the lifetime time horizon of the model.

Figure 6.

Tornado diagram of univariate sensitivity analysis of extension of Medicare coverage compared with no extension of Medicare coverage. The base case is represented by the horizonal dashed line with incremental costs of −$3077 and incremental QALYs of 0.37, with an expected value (EV) of −$8387 per QALY gained. The plausible range for each variable is displayed on the left. The red bar represents the change in ICUR with the upper limit of the plausible range for each variable, and the blue bar represents the change in ICUR with the lower limit of the plausible range for each variable. Costs identified by an asterisk were only included in the model for patients who had full Part A and B Medicare coverage, either through disability or given their age was >65 years. Variation in the inputs informing the annual cost after dialysis therapy after transplant failure, the proportion of patients still with Medicare coverage after 36 months after transplant, the risk of death after transplant failure and the overall risk of transplant failure had the largest effect on the ICUR estimate.

Figure 7.

Cost-effectiveness acceptability curves of the results of the probabilistic analysis for the incremental cost-effectiveness of extension of Medicare immunosuppression coverage compared with no extension of Medicare immunosuppression coverage. This graph shows the proportion of iterations where each option was cost-effective according to various cost-effectiveness acceptability (also known as willingness-to-pay) thresholds ($/QALY). In this analysis, extension of Medicare immunosuppression coverage was cost-effective in the majority of iterations regardless of the cost-effectiveness acceptability threshold.