To the Editor Using data collected over 25 years from the United Network for Organ Sharing database, Rana and colleagues1 recently reported in JAMA Surgery that more than 2 million life-years were saved by solid-organ transplant. In their seminal article on the survival benefits of kidney transplant, Wolfe and colleagues2 previously reported that the likelihood of survival became equal for patients treated with dialysis who remained on the waiting list and for those who underwent a transplant at day 244, with survival after day 244 favoring transplant recipients; this reflects the higher risk of death more proximate to transplant surgery. Wolfe and colleagues,2 in their analyses, evaluated transplant status in patients on the transplant waiting list as a time-varying exposure to correctly classify exposed vs unexposed person-time when determining mortality risk. In contrast, when estimating life-years saved, Rana and colleagues1 used the time spent on the wait listing as a common point of origin. Accordingly, we are concerned that Rana and colleagues1 dramatically overestimate the number of life-years saved by solid-organ transplant owing to immortal person-time bias in transplant recipients.3 Because Rana and colleagues1 estimated the number of life-years saved as a result of transplant using the time of transplant listing, patients receiving a transplant are required to survive until they receive the transplant, making them “immortal” for the entire time they spend on the waiting list; this contrasts with waiting list–only patients, who, by definition, can die at any time following initial listing prior to transplant. Therefore, with this approach, the survival time accrued between the time of listing and the time of transplant for patients who received a transplant is misclassified as survival that is due to the transplant. As a result, the benefit of a transplant is overstated. While, given prior studies,2,4,5 we are confident that a transplant has advantages over dialysis for most patients, the results provided by Rana and colleagues1 are fatally biased and therefore should not be used in clinical practice to frame the potential benefits of solid-organ transplant.
Foster MC, Varothai N, Weiner DE. Estimation of Life-Years Saved by Solid-Organ Transplant. JAMA Surg. 2015;150(10):1015. doi:10.1001/jamasurg.2015.1936