Preimplantation Genetic Testing (PGT): the new terminology for both PGS and PGD
The European Society of Human Reproduction and Embryology (ESHRE) and The American Society for Reproductive Medicine (ASRM), two of the most influential societies responsible for the regulation of the assisted reproduction techniques have established the term PGT (Preimplantation Genetic Testing) to refer to the test that analyses genetic material (DNA) of eggs or embryos to detect possible chromosomal abnormalities
Terminology in assisted reproduction is constantly evolving. Thus, new words are incorporated and modified in order to clarify the related concepts.
The European Society of Human Reproduction and Embryology (ESHRE) and The American Society for Reproductive Medicine (ASRM), two of the most influential societies responsible for the regulation of the assisted reproduction techniques have established a new term for the Preimplantation Genetic Diagnosis (PGD). This is now called PGT (Preimplantation Genetic Testing). The term refers to the test that is carried out to analyse the genetic material (DNA) of eggs or embryos. Through this test possible chromosome abnormalities can be detected. Depending on the concrete analysis which is carried out, some specific acronyms are added to the term:
PGT-A (Preimplantation Genetic Testing for aneuploidy):
It is used to diagnose numerical abnormalities (aneuploidies). These may be duplications or deletions (loss of a DNA fragment) of specific chromosomal areas. This term substitutes the old PGS (Preimplantation Genetic Screening). With this test, chromosome losses or additions are detected in embryos and, so, related diseases. Some examples are Down, Turner and Klinefelter syndromes.
PGT-M (Preimplantation Genetic Testing for monogenic diseases):
Helps to detect hereditary diseases caused by mutation or alteration of an only gen in the DNA sequence. Some examples are cystic fibrosis and sickle-cell anemia.
PGT-SR (Preimplantation Genetic Testing for structural diseases):
It is used to diagnose structural abnormalities. I.e., those that affect the structure of one or several chromosomes. This can happen by rupture or incorrect union of chromosomal segments. Translocations are abnormalities in which a chromosome is broken and a fragment is attached to another chromosome. Embryos that inherit this translocation could lead to babies that could be infertile in adulthood.