Tests for Down syndrome

The article was professionally consulted by Dr. Nguyen Anh Tu - Doctor of Obstetric Ultrasound - Prenatal Diagnosis - Obstetrics Department - Vinmec Hai Phong International General Hospital.

Down is one of the congenital, inherited syndromes with an abnormality on chromosome number 21. The disease causes the baby to be born with a different face, underdeveloped brain, dullness and a series of other abnormalities in the child. Therefore, tests to detect this syndrome are essential.

Child or adult suspected of having Down Syndrome . The fetus is at high risk for Down syndrome detected by prenatal screening tests. Pregnancy has factors that increase the risk such as: high maternal age, mothers who have had children with Down syndrome, fetus with abnormal signs detected by ultrasound.

Test Chromosomes – Set up chromosomes. QF-PCR assay. FISH test. 2.1 Chromosomes The normal human chromosome set consists of 46 chromosomes, divided into 22 pairs of autosomes and 1 pair of sexes. Each will have a characteristic size, shape and structure.
Set chromosomes - Chromosomes are a technique used to examine the chromosome sets in cells. After taking a sample (blood, amniotic fluid, placenta, umbilical cord, cord blood), the sample will be cultured in a special medium. After the appropriate time, they will be harvested and dyed characteristically. Currently, GTG (Giemsa trypsin G-banding) is the commonly used staining technique.
After staining, the number and structure of chromosome pairs were investigated microscopy at 1000x magnification and analyzed, stacked in complete sets using specialized software. In addition to Down syndrome, chromosomal mapping is also indicated for all subjects with suspected genetic disorders, birth defects, mental retardation, infertility - infertility or consecutive miscarriages...
2.2 QF-PCR assay QF-PCR stands for Quantitative fluorescence PCR, also known as quantitative fluorescence PCR. This is a technique used to amplify specific short DNA fragments, then labeled with a fluorescence signal and quantified by capillary electrophoresis.
QF-PCR is used to check the number of genes. Chromosomes commonly examined by QF-PCR are chromosomes 13, 18, 21, X, Y. Currently, QF-PCR is often indicated in rapid prenatal screening for chromosomal disorders for chromosomal disorders. high risk pregnancies with Down Syndrome, Edwards Syndrome, Turner Syndrome, Klinefelter Syndrome...

2.3 FISH technique FISH is a fluorescence in situ hybridization method. This is a cytogenetic technique used to determine the presence or absence of a specific DNA sequence on chromosomes.
The DNA probes are fluorescently labeled, then hybridize and attach to the corresponding positions on the chromosome you want to learn. Then, the hybrid chromosomes were examined under the microscope for fluorescence. The presence or absence of fluorescence signals the presence or absence of the corresponding specific chromosome.
FISH is often used to search for characteristics of DNA for diagnostic purposes, genetic counseling, treatment and identification of chromosomal mutations, species identification. In addition, FISH is also used to determine mRNA in the evaluation of gene expression in cells and tissues.
Currently, FISH is often indicated in rapid prenatal diagnosis of chromosomal disorders for high-risk pregnancies with Down syndrome, Edwards syndrome, Turner syndrome, Klinefelter syndrome...