Prenatal diagnostic FISH test

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

Detecting fetal chromosomal abnormalities is very important during pregnancy. Therefore, performing prenatal diagnostic tests to detect gene-related diseases will make screening more effective. Among them, FISH test is one of the very important tests.

FISH (Fluorescent in situ hybridization) is an intermediate technique between cellular and molecular genetics. Fish is performed using a chromosomal primer (NST) that is fluorescently tagged to detect a genetic abnormality on a particular chromosome.
Fluorescently labeled DNA probes will be hybridized to the corresponding positions on the human target chromosome. After hybridization, the product was observed under the microscope for the fluorescence signal of the hybridized probes. The presence or absence of a fluorescence signal helps to infer the presence or absence of the corresponding specific chromosome.
The advantage of this test is that it gives fast, specific and accurate results. In addition, FISH is very effective in detecting microdeletions or identifying the origin of certain types of gene translocations.

FISH test is indicated in the following cases:
Prenatal screening for fetal chromosomal abnormalities. Detection of some small gene deletions in genetic syndromes. The origin of the chromosome segments is unknown. Detection of cancer-specific chromosomal abnormalities.

Interphase FISH (or rapid FISH) is used to screen for some common genetic syndromes: Down syndrome (3 chromosomes 21), Patau syndrome (3 chromosomes 13), Edward's syndrome (3 chromosomes 18), Turner syndrome (only 1 X chromosome), Klinefelter syndrome (1 extra X chromosome)...
Advantages of fast FISH:
Fast: The test time is within 48 hours from the date of delivery. receive a sample of amniotic fluid. Complete testing quality control procedures after 4 days. High precision. The test is simple, requiring only about 10-20ml of amniotic fluid. Alternatively, the test can be performed on a placental specimen. However, decisions to terminate a pregnancy should not be based on FISH results alone.

Genetic syndromes caused by a small deletion on a chromosome, this abnormality is not detectable on conventional chromosomal formulas with an incidence of 1/5000 - 1/8000 live births. The FISH technique helps confirm the clinical and prenatal diagnosis for families with a history of having children with these syndromes.

Acute myeloid or lymphoid leukemia: FISH helps to evaluate chromosomal changes. In particular, the presence of some important translocations such as translocations of chromosomes 9 and 22 (Ph1), 4 and 11, 8 and 21... This is very valuable in classification. and prognosis of treatment. Neuroblastoma : Evaluation of chromosomal changes, especially NMYC gene duplication, loss of chromosome 1 short arm and addition of chromosome 7 long arm...