New DNA blood test can better identify rejection after a heart transplant

A new DNA blood test may reveal whether or not a heart transplant recipient will experience rejection from a donor organ.

The test can detect small differences in the circulating DNA of both the transplant donor and the recipient, gauging the likelihood of the transplanted organ surviving in its new environment. The developers of the test believe it could potentially eliminate the need for invasive heart biopsies in the future procedures that transplant recipients must undergo regularly to monitor organ rejection.

Nationwide, about a quarter to a third of all heart transplant recipients have one or more episodes of acute rejection. Its quite a clinically relevant problem, study co-author Kiran Khush, assistant professor of medicine at the Stanford University Medical Center, told FoxNews.com. Often times, the rejection is completely asymptomatic, which is why we continue to do regular screenings post-transplant.

In a new study published in the journal Science Translational Medicine, researchers from Stanford University detailed their new test, which focuses on detecting cell-free DNA pieces of DNA that circulate freely in the bloodstream.

During a transplant procedure, some of the donors heart cells are attacked and killed by the recipients immune system, causing them to release their genetic material into the blood. If the organ is rejected, a larger portion of heart cells are attacked, releasing a higher percentage of cell-free DNA in the bloodstream.

The DNA test can detect just how much of this donor cell-free DNA is circulating in the blood of transplant recipients.

What we do is we collect blood from the transplant recipient and donor at the time of transplantation. Their DNA is genotyped, so then we know the sequences of donor and recipient DNA and where they differ,Khush said. We then developed an analytic tool to determine the fraction of the DNA [in the recipients blood] that came from the transplant donor.

In a 2011 pilot study, Khush and her colleagues utilized this test on blood samples from a small group of transplant recipient-donor pairs. After analyzing their medical histories, the researchers found that the transplant recipients who didnt experience rejection had less than 1 percent of donor DNA in all of the cell-free DNA in their blood. Yet for those who underwent episodes of rejection, the percentage of donor DNA increased to about 3 or 4 percent during the event.

Hoping to expand on these findings, the Stanford team conducted a new, prospective study, analyzing 565 blood samples from 65 transplant patients, whom they monitored over an extended period of time. Using their test, they were able to accurately detect the fraction of donor DNA circulating in each patients bloodstream.

Overall, researchers found that they were able to predict two main types of rejection (antibody-mediated rejection and acute cellular rejection) in 24 of the patients who suffered moderate to severe rejection episodes. They also were able to detect signs of rejection up to five months before the traditional biopsies could find anything strange.

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New DNA blood test can better identify rejection after a heart transplant