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D.U.K. apie NIPT tyrimą
NIPT is non-invasive prenatal genetic testing, during which venous blood is taken from the mother, from which cell-free DNA is isolated and analyzed to assess the fetus's risk of chromosomal and genetic diseases. The assay includes automated sample preparation, sequencing, and sequencing data analysis.
This is a genetic blood test, during which circulating fetal DNA is isolated from the mother's blood plasma, in which, with the help of next-generation sequencing and bioinformatics analysis of the obtained data, changes in the genetic material of the fetus are searched for.
The NIPT test is non-invasive, so there is no risk to the mother and fetus.
Non-invasive prenatal testing is suitable both after natural conception and after an in vitro fertilization procedure, which is considered an increased risk factor for fetal abnormalities.
Only the venous blood of the pregnant woman is taken for the test to determine the genetic diseases of the fetus, so the biological father cannot be determined with this test.
VeriSeqTM NIPT Solution v2 test can be performed from the 10th week of pregnancy until the end of pregnancy.
The test is applied only for singleton and twin pregnancies. The test is not suitable for detecting polyploidy, such as triploidy and balanced chromosomal rearrangements (translocations). The examination is performed no earlier than the 10th week of pregnancy (10+0).
Results may be affected by:
- recent maternal blood transfusion;
- the mother underwent an organ transplantation/stem cell transplantation;
- maternal autoimmune diseases;
- benign and malignant tumors of the mother;
- maternal mosaicism;
- maternal copy number variation (CNV);
- placental mosaicism.
Saidė Genomics atlieka dviejų tipų NIPT tyrimus: bazinį N4 ir išsamų N6.
Bazinis N4 NIPT tyrimas naudojamas siekiant nustatyti įtakos vaisiaus sveikatai galinčių turėti chromosmų aneuploidijų riziką: Dauno sindromo (21 chromosomos trisomijos), Edvardso sindromo (18 chromosomos trisomijos) ir Patau sindromo (13 chromosomos trisomijos), lytinių chromosomų aneuploidijų riziką: Ternerio sindromo (45,X), Klainfelterio sindromo (47,XXY), XXX ir XYY, kai nėštumas yra vienvaisis. Išsamus N6 NIPT tyrimas papildomai nustato 7 Mb ar didesnio dydžio dalinių delecijų bei duplikacijų riziką bei visų likusių autosomų aneuploidijų riziką.
NIPT test results are available within 2-7 business days after the blood sample is delivered to the laboratory. If the test needs to be repeated, the response may be delayed.
Aneuploidy - an altered set of chromosomes, when one or more chromosomes from the normal set of chromosomes are absent (monosomy) or there are additional copies of them (trisomy, etc.), for example, Down syndrome (three copies of the 21st chromosome instead of two), Edwards syndrome ( three copies of chromosome 18 instead of two), Patau syndrome (three copies of chromosome 13 instead of two), Turner syndrome (one sex chromosome X instead of two XX), etc.
The risk that the fetus will have Down's, Edwards', Patau's syndromes, Turner syndrome and other disorders of the number of sex chromosomes and other chromosomal abnormalities is low. NIPT testing cannot detect chromosomal mosaicism, polyploidy, or rare monogenic diseases. However, having a low risk of chromosomal disease does not guarantee that the fetus will not have other abnormalities in fetal development that can be seen on ultrasound, such as brain, heart or spine abnormalities.
Vaisius turi didelę Dauno, Edvardo, Patau sindromų, lyties chromosomų, autosomų, dalinių delecijų ar duplikacijų riziką.
Pastabose nurodoma teigiama prognostinė vertė (PPV) – tikimybė, kad teigiamas tyrimo rezultatas bus tikrai teigiamas (vaisius iš tikrųjų turi anomaliją). Pavyzdžiui, jei PPV yra 95%, tai reiškia, kad iš 100 teigiamų testo rezultatų 95 iš jų yra tikrai teigiami.
PPV priklauso nuo tyrimo specifiškumo, jautrumo ir aneuploidijos dažnio, kuriam daro įtaką motinos amžius ir vaisiaus gestacinis amžius. Kadangi aneuploidijų dažnis didėja kartu su motinos amžiumi, kyla ir PPV vertė.
Pavyzdžiui vertinant 21 chromosomos trisomijos (Dauno sindromo) teigiamą prognostinę vertę 20-ies metų nėščiajai, ji sieks 46%, o 40-ies metų nėščiajai – 92% (tyrimo jautrumas, specifiškumas ir vaisiaus gestacinis amžius tas pats)
Kadangi NIPT yra atrankinės patikros tyrimas, negalima priimti galutinių sprendimų dėl nėštumo remiantis tik NIPT rezultatu. Norint patvirtinti diagnozę, reikia kartu su gydytoju genetiku apsvarstyti invazinio diagnostinio tyrimo, pvz., amniocentezės galimybę. Atlikus vaisiaus vandenų tyrimą, gali paaiškėti, kad NIPT metu nustatytas genetinis pakitimas yra būdingas pačiam vaisiui (diagnozės patvirtinimas), arba kad vaisius sveikas, bet pakitimas priklauso placentos audiniui (vadinamasis placentos mozaikiškumas) – tai taip pat reikšmingas rezultatas, nes placentos mozaikiškumas gali lemti sulėtėjusį vaisiaus vystymąsi gimdoje, tam tikras gimdymo komplikacijas ir kt.
During the NIPT test, the gender of the fetus is determined based on the free fetal DNA circulating in the pregnant woman's blood. If the Y chromosome is detected, the fetus is male, if the Y chromosome is absent, the fetus is female. In very rare cases, the sex of the fetus cannot be determined. One of the possible reasons is a twin pregnancy, where one of the twins is vanishing. In this case, it is possible that one of the fetuses is developing (female), but traces of the Y chromosome of the dead fetus (male) are still found in the mother's blood.
Free DNA fragments of both the mother and the developing fetus circulate in the mother's blood. The fraction of fetal/placental DNA fragments is called the fetal DNA fraction. Circulating free fetal DNA averages 10% of circulating maternal DNA, and its amount (fraction) increases progressively during pregnancy. A low fraction of fetal DNA (<3-4%) increases the chance of NIPT failure.
If the NIPT test fails, the test result cannot be provided. Such a test result can be determined by inappropriate blood sample collection, transportation or technical limitations, as well as individual physiological factors of the pregnant woman. After receiving an uninformative result, the Saide Genomics laboratory gives the patient the opportunity to perform the test again. One retest is free. If, after repeating the test, the answer is the same, depending on the possible reason for the failed test, consultation with a geneticist is recommended, who, if necessary, can order additional diagnostic genetic tests.
In order to confirm the diagnosis or make other decisions related to pregnancy, you cannot rely solely on the results of this test, it is necessary to consult with the doctor supervising the pregnancy. A positive test result requires consultation with a geneticist who may order additional diagnostic genetic tests, such as amniocentesis (amniotic fluid test) or chorionic villus biopsy, to confirm or deny a fetal chromosomal abnormality or other genetic disease.