Does having an organ transplant affect home genetic testing?
May 3, 2014 11:48 AM   Subscribe

My relative wants to take a 23andMe DNA test, but he has a heart and a kidney transplant (from 5 years ago). I have read about the possibility of chimerism (which I understand to be the presence of two sets of cells) in transplant recipients, and I am wondering if such a condition would affect the saliva-based DNA testing of 23andMe? And also, how common is this condition in transplant patients? Is there only really a pretty small chance that this will affect his test?
posted by foxinthesnow to Science & Nature (4 answers total) 1 user marked this as a favorite
Best answer: I would imagine for a saliva based test, the chances of the donors DNA showing up in saliva would be pretty slim from a heart and kidney transplant. Generally the transplanted organ cells replicate from the donor cells, so the actual organs will retain the donor DNA. So if they tested the heart or kidney cells, the DNA would be the donor's, not your relative. But I don't think it would affect the DNA in his saliva.

AFAIK, there are some situations where donor tissue may affect DNA tests in other systems - like a bone marrow transplant may affect the DNA in your blood, since red blood cells are made in bone marrow.

I assume that chimerism is more or less ubiquitous in transplant recipients, since the transplanted organs will retain the DNA of their donor.
posted by Lutoslawski at 12:23 PM on May 3, 2014

Best answer: Biology would indicate that having had a kidney and/or heart transplant should not affect the DNA in blood or saliva so your relative should be OK to have this analysis. 23andMe explicitly states those with bone marrow transplants should not pursue their testing but does not address other types of transplants. He could email them this specific questions if he wants.
posted by beaning at 1:08 PM on May 3, 2014

Best answer: I would say the chance of getting donor DNA in the recipient's saliva is practically zero. It's conceivably possible that some long lived white blood cells from the donor heart or kidney could survive in the recipient but the chance of these being in the recipient's saliva is very low.

In the case of bone marrow or other blood cell stem cell transplants, then the recipient's blood will certainly contain at least some cells (white blood cells since red blood cells don't really contain much, if any, genetic material though they may be derived from donor stem cells) that are derived from the donor stem cells and will have donor DNA. Unless the donor is the recipent's identical twin that DNA will be different.
posted by sevenless at 1:10 PM on May 3, 2014

Best answer: Actually, you can develop heme chimerism and the ugly version (graft versus host disease) after solid organ tansplant, since there are usually some blood stem cells hanging around in the organ. This is much more common (but still rare!) in highly vascular organs like liver than kidney. I doubt that the cells in saliva will be highly affected. The genotyping platform 23andMe uses will tell you if you're chimeric; it will come through as a QA problem with many SNPs unable to resolve the genotype. If you have a small fraction of the DNA in your saliva coming from donor cells, then it shouldn't be a problem at all.

Finally, the main use of 23andMe's data at this point is ancestry determination. You can your donor likely have very similar ancestry, as otherwise you would not be very good tissue matches.
posted by a robot made out of meat at 1:29 PM on May 3, 2014 [5 favorites]

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