Late episodes of acute rejection carry higher risk of graft loss

Acute rejection events become less frequent with time since transplantation, but later events may have a greater impact on graft survival, suggests a report in Transplantation.

The researchers analyzed U.S. Renal Data System data on 48,179 kidney transplantations from 2000 to 2007. The Organ Procurement and Transplant Network was used to gather data on acute rejection events, which were classified as antibody-treated or not. Acute rejection was analyzed for association with all-cause graft loss, by use of a time-varying Cox regression approach.

The rate of non–antibody-treated acute rejection events (per 100 graft-years at risk) decreased from 9.93 6 months after transplantation to 8.43 at 12 months, 5.71 at 24 months, and 4.70 at 36 months. The rate of non–antibody-treated acute rejection was more than double the rate of antibody-treated events, across risk periods and donor types. Antibody-treated events were associated with a higher risk of graft loss than were non–antibody-treated events.

For antibody-treated acute rejection, the relative risk of graft loss increased with the time between transplantation and the rejection event. By contrast, the risk from non–antibody-treated events was highest 13 to 24 months after transplantation. Regardless of when acute rejection occurred, the associated risk of graft loss was higher in the first 89 days after the event, compared with 90 days and later.

This large study helps to clarify the rates and clinical impact of acute rejection after kidney transplantation. Acute rejection occurring a longer time after transplantation may have a greater impact on the risk of graft loss, with risk being highest less than 90 days after the event [Lentine KL, et al. The implications of acute rejection for allograft survival in contemporary U.S. kidney transplantation. Transplantation 2012; 94:369–376].