Multi-state models preferable to measure graft risk among kidney transplant recipients
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Compared with the Kaplan-Meier estimator, researchers found multi-state models provided a more accurate and comprehensive assessment of the life course and graft risk of older kidney transplant recipients.
“As a result of excellent graft survival in older patients and, inevitably, relatively high mortality, most older kidney recipients can expect to die with a functioning graft. Also noteworthy is the fact that there is an increased rate of early graft failure in elderly patients, at least in part due to higher use of expanded criteria kidneys in this age group,” Thomas Vanhove, MD, PhD, from Massachusetts General Hospital at Harvard Medical School in Boston, and colleagues wrote. They added, “It is likely, however, that some of the limitations of conventional outcome metrics (particularly death with functioning graft and death-censored graft failure) are amplified in older patients, with possible implications for the accuracy and comprehensiveness of these metrics.”
Researchers explored the relationship between kidney transplant recipient age and the degree of event rate overestimation among 238,123 adult recipients of a first-time single kidney transplant between 2000 and 2017. Data were derived from the Scientific Registry of Transplant Recipients.
Researchers conducted age-stratified unadjusted Kaplan-Meier and competing risk survival analyses on the cohort. Results were then compared with a multi-state model that included five states (alive with functioning graft, death with functioning graft, graft failed [alive], retransplanted and death after graft failure).
Compared with competing risks or multi-state models, the Kaplan-Meier showed an age-dependent overestimation of the risks of graft failure and death with functioning graft. Patients aged 75 years or older showed a fourfold absolute overestimation of the risk of death with functioning graft compared with patients younger than 55 years. Additionally, the multi-state model revealed patients aged 55 years or older undergoing transplant were at a 4% or lower chance of being back on dialysis at any point after transplant.
Overall, the 2-year mortality after graft failure was 38%, 54% and 67% in recipients aged 55 to 64 years, 65 to 74 years and at least 75 years, vs. 20% in those younger than 55 years.
“In summary, multi-state models can describe the entire posttransplant trajectory in a single analysis, do not suffer from the potential overestimation of event rates that may occur with Kaplan-Meier analyses and readily incorporate outcomes, such as events after graft failure, that are not always reported. This appears particularly relevant to obtain accurate estimates of the expected posttransplant course for older recipients,” Vanhove and colleagues wrote. “Multi-state models may be a useful adjunct to traditional survival analyses when reporting unadjusted outcomes after kidney transplantation, particularly when using time frames longer than 5 years posttransplant.”
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