2012-05-19
Prenatal FISH (13, 18, 21, X ir Y chromosomes) (amniotic fluid)
FISH (fluorescence in situ hybridization) is molecular cytogenetic technique used to identify specific chromosome or chromosome part. FISH enable to detect fine changes in chromosome that are undetectable by common cytogenetic methods. Today FISH method is widely used in cancer diagnostic worldwide.
In FISH test there is no need to grow cells (blood, bone marrow or amniotic fluid) in special media, and this shortens duration of the test. Cells are directly put on a slide and exposed with special genetic markers (probes), tagged with special fluorochrome dye. Cell nuclei are examined in the noncycling state using fluorescence microscope. Fluorescence is seen in the places of probe fixation.
Test is extremely accurate as it is based on the complementary interaction of nucleotides, but not on the experience of investigator. FISH method enables to examine more cells compared with classical genetic approach, and therefore this method is more reliable.
FISH test is successfully used in the SORPO medical research center for prenatal diagnostic. Using amniotic fluid starting at 10th – 12th week of pregnancy chromosomal diseases are determined in unborn baby.
In this test specific chromosomes associated with common genetic diseases, such as Down syndrome, Edwards syndrome, Patau syndrome, are evaluated as well as changes in quantity of X and Y chromosomes. Changes in quantity of 13, 18, 21, X and Y chromosomes are determined during one test.
Advantages of FISH test:
•Test is fast. FISH test results are presented in 2-3 days after start of the test. It is a great advantage as time of uncertainty and anxiety, lasting for pregnant woman from amniocentesis to the presentation of test results, is significantly shortened.
•Test may be performed in any stage of pregnancy starting at 10th – 12th week of pregnancy.
•In one test changes in quantity of 13, 18, 21, X and Y chromosomes is determined. These are the most common chromosomal abnormalities:
Trisomy 13: Patau syndrome
Trisomy 18: Edwards syndrome
Trisomy 21: Down syndrome
•High reliability. Accuracy of FISH test performed using “Aneu Vysion EC” (Abbot Laboratories, USA) kit for prenatal diagnostic is 99,99 %.
In FISH test usually selected specific chromosomes are examined, but not the whole karyotype.
FISH method is recommended:
•when other findings (ultrasound, PRISCA) are suspicious for chromosomal abnormalities;
•when mother is > 35 years old;
•when exposure of mutagenic factors is suspected;
•when child with chromosomal abnormality was born in the family.
Amniotic fluid examination is performed from Monday to Wednesday. Test results are presented after 2-3 days. Specimens of amniotic fluid are obtained by obstetrician-gynecologist in healthcare institutions.