Virtual Crossmatching Allows Faster Kidney Transplantation

By Will Boggs MD

February 12, 2020

NEW YORK (Reuters Health) - Kidney transplantation can be safely performed with virtual crossmatching of donor and recipient without the need for a prospective physical crossmatch, according to a retrospective review.

"We think virtual crossmatching should become the standard of care for the majority of patients," Dr. Vinayak S. Rohan of the Medical University of South Carolina, in Charleston, told Reuters Health by email.

Prior to kidney transplant, donor-recipient compatibility is assessed by physical crossmatching, usually by flow cytometry, at most programs. Virtual crossmatching (VXM) relies on complete HLA typing of the donor and current antibody assessment of the recipient, which can be performed quickly and allows for timelier organ allocation decisions.

Dr. Rohan and colleagues compared kidney transplant outcomes, principally the mean cold ischemic times (CIT), between 505 patients transplanted before their 2017 implementation of VXM and 227 patients transplanted using VXM.

After implementation, the mean CIT decreased from 16.67 hours to 14.5 hours (P=0.002), the researchers report in Journal of the American College of Surgeons.

Delayed graft-failure rates did not differ significantly between the pre-implementation (19%) and post-implementation (17%) eras, even though there were more donation after cardiac death (DCD) and higher (less favorable) Kidney Donor Profile Index (KDPI) donors in the post-implementation era.

The rates of one-year graft loss, patient death and biopsy-proven acute rejection rates did not differ between the two eras.

In multivariable modeling that adjusted for baseline characteristics, patients transplanted in the post-implementation era had an estimated 2.35-hour reduction in CIT (P<0.001) and 26% lower odds of developing delayed graft failure (P=0.17).

"We have known for years that VXM is a safe technology," Dr. Rohan said. "This article not only reaffirms the safety of VXM, but also the outcomes, in terms of cold ischemia times and delayed graft function."

"The ability to predict the crossmatch and schedule the operation in advance leads to less potential 'middle of the night' transplants, improving quality of life not only of patients but surgeons as well," he said.

Dr. Raja Rajalingam of the University of California, San Francisco, who recently showed that a VXM-based strategy facilitates sharing of DCD kidneys for highly sensitized recipients, told Reuters Health by email, "Virtual crossmatching should become the standard of care at the national level."

"It is considered to be challenging to perform virtual crossmatch for broadly sensitized patients (due to previous transplantation, pregnancies, and blood transfusions)," said Dr. Rajalingam, who was not involved in the new research. "However, it is not clear how many of the 29 (broadly sensitized) patients (in this study) received a kidney transplantation based on virtual crossmatch."

He expressed surprise that the decrease in CIT was only about two hours with VXM. Based on the four to five hours required to perform pretransplant flow cytometry physical crossmatch, he would have expected a greater reduction.

SOURCE: Journal of the American College of Surgeons, online February 5, 2020.