Značaj ukupne i fetalne slobodne DNA iz majčine krvi u neinvazivnom otkrivanju fetalnih aneuploidija [The significance of total and fetal cell free DNA from maternal blood in noninvasive detection of fetal aneuploidies]

Bekavac Vlatković, Ivanka (2015) Značaj ukupne i fetalne slobodne DNA iz majčine krvi u neinvazivnom otkrivanju fetalnih aneuploidija [The significance of total and fetal cell free DNA from maternal blood in noninvasive detection of fetal aneuploidies]. PhD thesis, Sveučilište u Zagrebu.

PDF Download (1MB)

Abstract

INTRODUCTION: Chromosomal abnormalities account for approximately 15% of the major congenital anomalies before the age 1 year in Europe, and are associated with 25% of perinatal deaths due to congenital anomalies. Maternal serum is routinely analyzed in pregnant women to screen for chromosomal abnormalities such as Down and Edwards syndrome. In addition there are many reports of an association between abnormal levels of individual analytes and poor fetal or placental health. A low pregnancy-associated plasma protein A (PAPP-A) in the first trimester indicates a high risk for Down and Edwards syndrome while hCG is elevated in pregnancies with trisomy 21. It was realized that the great majority of fetuses with major aneuploidies can be identified by a combination of maternal age, fetal nuchal translucency thickness and maternal serum biochemical markers. With a false positive rate of 5% this approach identifies up to 90% of fetuses with trisomy 21 and other major aneuploidies. Since 1997, when fetal cfDNA in maternal circulation was discovered, a new field of research has emerged driven by its potential clinical application for noninvasive prenatal diagnosis. Quantitative aberrations of fetal and maternal cell free DNA were noticed in chromosomal aneuploidies. We aimed to quantify the levels of fetal and total cell free DNA on prospectively collected samples, to understand their correlation with other variables and clarify their diagnostic value. MATERIAL AND METHODS: Total an fetal cell free DNA pre CVS was extracted from maternal plasma from 56 pregnancies with aneuploid fetuses and 56 samples from chromosomally normal group and quantified using real time PCR. RESULTS : Analysis of total and fetal cell free DNA levels showed no correlation with crown-rump length. Furthermore there was no significant association between maternal serum biochemical markers in first trimester ( PAPP-a and βhCG) in both groups on cell free fetal or total DNA. Additionally, analysis of cell free total DNA revealed differences between chromosomally normal and aneuploid fetuses, the median total DNA level in aneuploid group was significantly lower than in control group (p=0,001). Furthermore fetal fraction was 6% and did not differ between control group and group with aneuploid fetuses. CONCLUSION: Our results suggest that quantification of total cell free DNA might be an prognostic marker of chromosomal aberrations in first trimester pregnancy. Low correlation between first trimester maternal biochemical markers and total cell free DNA may improve screening performance. Furthermore high association between maternal cell free DNA levels and aneuploid fetuses suggest that placental factors are also affecting maternal cell death. However gaps exist what affects the production, metabolism and clearance of fetal and maternal cell free DNA.

Abstract in Croatian

UVOD: Prenatalna skrb značajnim dijelom obuhvaća metode probira u svrhu otkrivanja trudnica visokog rizika rađanja kromosomski bolesnog ploda. U većini razvijenih zemalja standardni postupak izračuna individualnog rizika rođenja djeteta s kromosomopatijom uključuje korištenje neke od neinvazivnih metoda probira (najčešće se radi o kombinaciji ultrazvučnog i biokemijskog probira), te postavljanje konačne dijagnoze uzimanjem fetalnog uzorka invazivnim zahvatom ukoliko individualni rizik prelazi zadanu granicu rizika od 1:250. Posljednje desetljeće značajno mjesto zauzimaju istraživanja o upotrebi slobodne fetalne i ukupne DNA u razlikovanju normalnih od patoloških trudnoća. CILJ: Određivanje značaja kvantifikacije fetalne i ukupne (fetalne+majčine) slobodne DNA iz majčine krvi u procjeni rizika rađanja kromosomski bolesnog ploda u prvom tromjesečju trudnoće. REZULTATI: Kod aneuploidnih plodova vrijednosti ukupne slobodne DNA u optoku majke su statistički značajno snižene u prvom tromjesečju u odnosu na trudnoće s urednim kromosomskim statusom ploda (p=0,001). Trudnice čija je vrijednost ukupne slobodne DNA <=0,0298 ng/μL imaju 5,47 puta veći rizik nositi aneuploidan plod u odnosu na trudnice koje imaju više vrijednosti ukupne slobodne DNA. Vrijednost ukupne slobodne DNA značajno je negativno korelirala s veličinom nuhalne prozirnosti u usporednoj skupini. U obje skupini nema značajne povezanost vrijednosti ukupne i fetalne slobodne DNA u optoku majke sa drugim serumskim biljezima majke (βHCG i PAPP-A). Fetalna frakcija u optoku majke u našoj populaciji u razdoblju od početka 11. do kraja 13. tjedna trudnoće iznosi 6% bez značajne razlike između skupine trudnica sa aneuploidnim plodom i usporedne skupine ZAKLJUČAK: Postojanje statistički značajne povezanosti promjene ukupne slobodne DNA, što se prvenstveno odnosi na majčinu komponentu upućuje na značaj mehanizama placentacije na apoptotičke procese i otpuštanje slobodne DNA majke. Stabilne vrijednosti ukupne slobodne DNA i neovisnost o drugim serumskim biljezima majke čine ukupnu slobodnu DNA mogućim dodatnim čimbenikom probira u prvom tromjesečju trudnoće. Daljnja istraživanja potrebna su za bolje razumijevanje stvaranja, metabolizma i značenja vrijednosti ukupne i fetalne slobodne DNA, te promjene njihovih vrijednosti u normalnim i patološkim trudnoćama.

Actions (login required)

View Item

Downloads