Survival Following Transplant
Why might outcomes following transplant be important to me?
Understanding the likely outcomes while waiting for transplant and following transplant are important in understanding care options and choices. Outcomes following transplant are among the key metrics SRTR publishes for each transplant program. SRTR considers two key outcomes following transplant:
- Patient survival: What is the likelihood that a patient will be alive at a certain time posttransplant, for example, one-year?
- Graft survival (survival with a functioning transplanted organ): What is the likelihood that a patient will be alive with a functioning transplanted organ at a certain time posttransplant, for example, one-year?
For each metric, SRTR publishes outcomes in the program-specific reports at three different time points: one month, one year, and three years. Longer-term outcomes are also important, and SRTR publishes national trends in long-term outcomes for each transplant type in the SRTR/OPTN Annual Data Report.
What do the various metrics mean?
In the program-specific reports, you will find various metrics detailing patient and graft survival. Each is described in the following table, which assumes we are looking at first-year patient survival:
|Estimated survival||94.3%||Estimated survival is an estimate of the percentage of patients surviving at one year after transplant. In this case, we estimate that just over 94% of the program's transplant recipients were alive at one year after transplant. It is estimated because we do not have a full year of follow-up for all the patients we are evaluating. For some patients who underwent transplant close to the time we calculate the metric, we may only have six months of follow-up to observe. SRTR uses standard survival analysis techniques to handle these cases and arrive at an estimated survival percentage.|
|Expected survival||93.2%||Expected survival is a measure of the percentage of patients SRTR expected to be alive at one year based on the types of patients who underwent transplant at the program and the quality of the donor organs that were used. In this case, we expected just over 93% of the patients to be alive at one year posttransplant.|
|Hazard ratio||0.95||The hazard ratio is a measure of this program's outcomes relative to expected outcomes. A hazard ratio of 1.0 means the program's survival rate was exactly as expected based on national experience with similar transplant recipients and donor organs. A number less than 1.0 means the program’s survival rates were better than expected; a hazard ratio of 0.75 means the program had 25% fewer deaths than expected (1.0 minus 0.75 = 0.25, or 25%). Likewise, a hazard ratio greater than 1.0 means the program’s survival rates were worse than expected; a hazard ratio of 1.34 means the program had 34% more deaths than expected (1.34 minus 1.0 = 0.34, or 34%).|
How are these numbers calculated?
These survival data are calculated using two basic components:
- The number of observed graft failures or patient deaths during the evaluation window, and
- The number of expected graft failures or patient deaths during the evaluation window.
The expected number of events is calculated using complex statistical models that take into account many patient and donor characteristics in an attempt to estimate the likely outcome for each transplant.
You can find detailed information in the analytic methods and in the paper Bayesian methods for assessing transplant program performance (Salkowski N, Snyder JJ, Zaun DA, et al. Am J Transplant. 2014;14:1271-1276).
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