Update: The largest known clinical study of nips discusses the testing of placental DNA.
One of the first conference attendees to walk up to talk about my poster was a medical geneticist that, we figured out, was stationed with me when I was in the United States Air escort sans sexe Force.
Turns out I was wrong.But, I would guess that expectant mothers would think differently on the accuracy of a test if it were explained to them that the test did not actually test fetal DNA, but instead was cell free placental, dNA.The presenter on the false positive based on placental mosaicism concluded by saying that because nipt tests placental DNA, the most it can ever become is as accurate as a CVS.Nipt Brands, for years, Ive been presenting at conferences on prenatal testing for Down syndrome, explaining how the new tests are based on cell free fetal DNA or cffDNA.Well, this everyone did not.While CVS is considered a diagnostic test, CVS results still have the risk, however slight, of returning results from a mosaic placental cell that is not represented in the fetus itself.This past week I gave a poster presentation at the Annual Clinical Meeting for the American College of Medical Genetics (acmg).Indeed, the diagnostic test that can be performed in the first trimester, chorionic villus sampling (CVS tests placental cells, and has returned results of Down syndrome even when the fetus does not have Down syndrome, because the particular placental cells tested had a triplicate.2 Implantation of blastocyst, it turns out, that almost all of the cffDNA found in the maternal blood stream actually comes from the DNA of the cells that form the placenta or perform the anchoring function, not the cells that form the fetus.In the vast majority of cases, the results will be accurate for the fetus even when the test is of placental DNA.
Therefore, its not entirely accurate to use cell free fetal.When a conceived cell implants into the mother, the cell has divided into further cells that perform certain functions.In the professional medical committee opinions and materials from the testing laboratories, where reference is made, often it is to cell free fetal DNA.As a fellow conference attendee explained, this is a distinction without much difference; while it is not cffDNA, in his opinion, it was not that big of a deal to refer to it as cffDNA.In placental mosaicism, the placenta can have cells with triplicates of chromosomes while the fetus does not have any triplicate chromosomes in its cells.Mothers will expect prenatal tests to be of fetal DNA, not placental DNA.Placental versus fetal DNA may be a distinction without much of a difference when it comes down to the accuracy of the results.
But, this is more than just a semantical differenceor, even if that is all it isthen there is a significant semantical reason why fetal DNA was chosen over the more accurate placental DNA.
There is where I learned I was mistaken about the basis for newest form of prenatal testing.