Effectiveness of Standart Cytogenetic Analysis in Conjuction with Fluorescent In Situ Hybridization (FISH) in Prenatal Diagnosis
About the author:
Gontar J., Ilyin I., Fedota A., Pidchenko T.
METHODS AND METHODOLOGIES
Type of article:
The paper introduces the necessity of prenatal diagnosis, to demonstrate the benefits of combining different approaches for identifying markers of chromosomal aberrations and identification of chromosomes of the fetus. The main indications for prenatal diagnosis are the mother’s age, the presence of hereditary diseases, bur- dened obstetric history (miscarriage), abnormalities in biochemical screening of pregnant woman’s blood, devia- tion from the norm in the study of placental hemodynamics (Doppler), detection of developmental disorders of the fetus by ultrasound study in the first (indicators of nuchal translucency, size mismatch or absence of the nasal bone) and in the second trimester of pregnancy. To clarify and identify violations of fetal development in the prenatal diag- nosis used invasive and non-invasive methods. The non-invasive methods include study of fetal cells that circulate in the mother’s bloodstream, ultrasound in two-, three-, four-format, magnetic resonance imaging (MRI). Invasive techniques include biopsy of chorionic villi or placenta, amniocentesis, cordocentesis, fetal tissue research. First of all prenatal diagnosis aims to detect the most common chromosomal aberrations trisomy 21 or Down syndrome, which remains the greatest single autosomal trisomy with 1. 5 per 1,000 live births. Primary data collection was held on the basis of cytogenetic laboratory of “Medical Center IGR” (director – Ilyin I., PhD) in the period from 2009 to 2013. In this study the main method of invasive procedures to obtain fetal ma- terial was amniocentesis. Aspiration of amniotic fluid was performed in a volume of 15-20 ml. After aspiration the fluid were cultured, fixed, and then produced a standard cytogenetic analysis. Native amniotic fluid was used for molecular cytogenetics by fluorescence in situ hybridization. In this case were counted 100 interphase nuclei of amniotic fluid cells with the registration of signals from chromosomes 13, 18, 21, X, Y. The study was based on data from 407 amniocentesis results of standard cytogenetic and molecular cytogenetic analysis. The most common chromosomal abnormality was detected the trisomy 21 (5. 6 %). The main indications for prenatal diagnosis of these patients were biochemical screening (38. 09 %), nasal bone hypoplasia (28,57 %), in- creased nuchal translucency (19. 5 %) and others. The highest risk by biochemical screening was 1:2, the lowest – 1:117. In the investigation of native amniotic fluid of the same patients the quantitative chromosomal abnormalities were detected in 100 % of cases within 12-24 hours after an invasive procedure. Using of FISH technique were established cases of trisomy 21, trisomy 18, monosomy X (full and mosaic forms), triploid set of chromosomes in the short term, and confirmed the balance of the chromosome set of fetuses in the presence of chromosomal rearrangement one of a parent. This determination is very important, especially in cases where chromosomal rear- rangements involving small regions of different chromosomes. Application of FISH is indispensable in cases where it is impossible to get the result of the standard cytogenetic studies because of the low mitotic index of the cell cul- ture, as well as the absence of cell growth due to the non-perception of the individual components of the nutrient medium, which occurs in 1-2 % of cases. So, the warning of children born with a chromosomal abnormality is one of the most important tasks of modern medicine and genetics in particular. Karyotyping of couples before planning pregnancy should be one of the es- sential steps in genetic counselling to identify structural peculiarities that may be displayed on the chromosomal balance of germ cells, and later on the chromosome set of the embryo. Patients who enter into the risk group should undergo additional preimplantation genetic screening of embryos (PGS), which is the most effective method to prevent the chromosomal abnormalities of the fetus. It is a comprehensive approach to pregnancy planning and correct counselling is a major challenge for the future investigations.
trisomy 21, karyotype of the fetus, amniocentesis, invasive prenatal diagnosis
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Publication of the article:
«Bulletin of problems biology and medicine» Issue 4 part 1 (113), 2014 year, 238-243 pages, index UDK 575. 155