Answer from: Raúl Olivares, MD
PGS is a technique with high accuracy with the current technology that we are using NGS, we can offer our patients 99% efficiency in detecting abnormalities. It could not be as high as amniocentesis, and this is just because of the number of cells that we have to study. In a standard PGS, we are going to work with 3 to 5 cells. In a standard amniocentesis, we may get 15, 25, or 50. The more cells we have, the more reliable the result is going to be, but the difference is very low. As I’ve said, we offer 99% in PGS and 99.8% in amniocentesis. In comparison, if you do the PGS, what you are going to do is get the results before even the patients get pregnant, and if we do that, we are going to help the patients to avoid having, for example, to decide a termination if the amniocentesis is abnormal. Whenever there is an indication to carry out a genetic test, in our opinion, it’s much better to carry out PGS and avoid the pregnancy than let the patients get pregnant and end up with termination if the amniocentesis is abnormal.
Answer from: Luca Gianaroli
Like any technology, the accuracy of the test has improved a lot over the years. Generally, we can say that the risk of misdiagnosis is limited to 1-2%. The major problem that we are encountering is that the embryos or the part of the biopsied embryo could not represent the internal results of the entire embryo.
At that stage of development, the embryo can be a so-called mosaic embryo. This means that a few cells of the mosaic embryo tell us one thing about the number of chromosomes; whilst the entire embryo actually gives a completely different image in terms of chromosomes. This is a risk that you have to take. It is probably why you could still have a misdiagnosis in some cases due to not picking up a group of cells that represent an entire embryo.
What is the accuracy of the PGS tests?
Is PGS testing accurate? Can we totally rely on this test? Can PGS provide a false result?