Detecting the first signs of organ transplant rejection could be as easy as measuring levels of organ donor DNA in the transplant recipient's blood, a new study suggests.
Currently, surgical biopsies are required to track the health of donated organs. Heart transplant recipients in particular have to undergo at least 12 biopsies in the first year of their transplant to make sure their body is accepting the new organ, and then two or three a year for the next four years, researchers said.
But a simple blood draw could eventually replace those biopsies, as well as decrease the need for anti-rejection medications that come with a host of side effects such as diabetes, hypertension and renal problems, said Dr. Hannah Valantine, professor of cardiovascular medicine at Stanford University School of Medicine in California.
“What we've seen in those biopsies is damage and breakage of the heart muscle,” Valantine told MyHealthNewsDaily. “This blood test, which shows the elevation in the level of the donor DNA, occurs a long time before that biopsy gets harvested.”
The study was published online March 28 in the journal Proceedings of the National Academy of Sciences.
Valantine first pioneered blood tests to diagnose organ rejection in 2010, when she developed a test that detects expression of 20 genes in the patient's blood to see if the body is attacking the new organ. But in this new technique, developed by Stanford bioengineering professor Stephen Quake, the levels of organ DNA, specifically of certain chromosomes, in the blood are tested as a sign of early rejection. Females have only X chromosomes, while males have X and Y chromosomes.
Valantine and her colleagues gathered blood samples from 39 women who received heart transplants from men (and would therefore have Y chromosomes in their blood from the donor organ), and tested the amount of donor DNA in their blood.
The researchers found that women whose bodies were rejecting the donor hearts had an increase in Y chromosomes in their blood, from the normal 0.5 percent to 8 percent, the study said.
Then, researchers tried seeing if the test worked even in men who received male hearts (who would therefore already possess Y chromosomes) by identifying genome segments unique to the donor. They applied the technique to three women and four men who all received hearts from male donors.
They found that the blood test accurately predicted early organ rejection, even in the men. Donor DNA levels of 3 to 4 percent in the blood, up from the norm of about 0.5 percent, signaled early organ rejection, the study said.
Donor DNA “really rises precipitously just before the rejection,” Valantine said.
What's at stake
The sooner organ rejection is identified, the fewer drugs that are needed to control the rejection, Valantine said.
Usually when doctors do a biopsy and find that there is organ rejection, they give steroidal medications to the patient that can cause serious side effects.
But since the blood test catches rejection early on, doctors would be able to give the patient a smaller dose of anti-rejection medication, or even just increase the dose of the maintenance immunosuppressive drugs the patient has to take anyway, she said.
The ultimate hope is to eliminate the need for biopsies, Valantine said.
“If we see the blood level [of donor DNA] going up and we took a biopsy, chances are we would be getting it before the biopsy is even able to come back positive,” Valantine said. “And if we wait for the biopsy to be positive, it wouldn't add anything” because the blood test would have already detected the early rejection.
Biopsies are a bit like mini-surgeries for heart transplant patients, she said. Patients must go in to the doctor, where a needle tool is inserted into the neck to snip off part of the heart for testing. The patient must be given a local anesthetic for the procedure, and two to three years' worth of biopsies usually leads to scarring, Valantine said.
“It's unpleasant for the patient, and costly,” she said.
Now, Valantine and her colleagues are applying for a patent for the blood test. They also plan to conduct a study that tracks transplant recipients over time as they are administered blood tests to track organ rejection.
Pass it on: A simple blood test could predict early organ rejection for heart transplant patients.
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