Preimplantation genetic diagnosis (PGD) An update review of biopsy sample, technique, and diagnosis method

Preimplantation genetic diagnosis (PGD) is a genetic screening technique for embryos to be implanted in assisted reproductive technology or in vitro fertilization (IVF). PGD requires several stages and manipulation of gametes and embryos. Unfortunately, PGD is not always successful. This review was aimed to reveal the update of PGD, in term of biopsy sample, biopsy technique and its diagnosis technique. A computerized search of PubMed and google scholar database was conducted for general terms such as “preimplantation genetic diagnosis”, “polar body“, “cleavage“and “blastocyst“and followed by screening and evaluation of collected proper accordingly. In PGD, sample of biopsy can be obtained from (1) polar body of oocyte (2) blastomere of cleavage stage of embryo and (3) trophectoderm cells of blastocyst. The process of sloughing off the oocyte or embryo cell can be done through several techniques, namely Mechanical Partial Zone Dissection (PZD) which is carried out using two pipettes, namely holding pipette to hold the embryo and injection pipette to slit the blastomere/cell out of the embryo, while the Chemical Drilling Zone is done by using acid tyrode (pH 2.3) to create holes in the membrane, and Laser-assisted Dissection which is done by opening the zone through a laser that enters the located area of oocyte/embryo. Then, diagnostic methods are used to detect the abnormalities found, such as Polymerase Chain Reaction (PCR) which is used for diseases caused by single gene disorders, Fluorescence In Situ Hybridization (FISH) which is used to detect chromosomal abnormalities, Array Comparative Genomic Hybridization (Array CGH) which is used to investigate aneuploidy in oocytes, and gene expression could be evaluated on mRNA representing the genetic function of oocyte development. The most appropriate update of PGD is polar body for the sample, laser-assisted dissection for the technique and CGH for the diagnosis method.