Non-Invasive Prenatal Test: Discover neoBona Genomewide

Prenatal screening is an essential process in monitoring pregnancy to ensure the health of both the mother and the baby, including screening for possible fetal genetic anomalies. Among the most advanced and less invasive methods available today, the Non-Invasive Prenatal Test (NIPT) stands out, analyzing circulating free fetal DNA (cfDNA) present in maternal blood.  

This article details what NIPT is, how it is performed, and its main applications, providing valuable information for doctors and laboratory professionals looking to stay updated on advances in prenatal diagnostics. 

Check out the full article on NIPT here on our blog. 

What is a non-invasive test? 

Non-invasive tests are diagnostic or screening procedures that allow the evaluation of health conditions without the need for physical penetration into the body, avoiding risks associated with invasive methods such as infections and surgical complications.  

They use techniques such as ultrasonography, magnetic resonance imaging and analysis of simple biological samples like blood, urine and saliva, providing a safe and effective approach to obtaining information about an individual’s health or condition. In the prenatal context, non-invasive tests, such as the Non-Invasive Prenatal Test (NIPT), analyze the cfDNA present in maternal blood to primarily identify chromosomal abnormalities.  

The discovery of free fetal DNA fragments in maternal blood, along with the development of large-scale DNA sequencing methods, has revolutionized options for prenatal diagnosis (1).  

Previously, the assessment of chromosomal abnormality risk was conducted using an algorithm that combined the measurement of pregnancy-associated proteins in maternal serum with ultrasound data, allowing for the estimation of fetal risk. Currently, screening with NIPT has increased diagnostic sensitivity and specificity, reducing the false positive rate. As a result, the selection of patients needing invasive methods has been improved compared to traditional screening. 

What is the non-invasive prenatal test (NIPT)?

NIPT (non-invasive prenatal testing) involves analyzing circulating free fetal DNA (cfDNA) present in maternal blood to screen for fetal chromosomal abnormalities through a minimally invasive maternal venous blood draw. 

Previously, conventional first trimester screening (ultrasound and serum biomarkers) allowed for the detection of the most common chromosomal abnormalities in the fetus during pregnancy, with a sensitivity of 85-90% and a false positive rate of 5% (2). 

This strategy has been primarily aimed at detecting major aneuploidies (alterations in the number of chromosomes) such as, for example: 

• Trisomy of Chromosome 21: Down Syndrome; 

• Trisomy of Chromosome 13: Patau Syndrome; 

• Trisomy of Chromosome 18: Edwards Syndrome.

How is NIPT performed? 

NIPT was introduced into clinical practice in 2011, primarily by private laboratories, where the use of circulating free fetal DNA (cfDNA) has become a reality in prenatal routine, and its use has been increasingly expanded (3).  

cfDNA consists of short DNA fragments, which mostly come from trophoblastic cells of the placenta. The percentage of cfDNA derived from the trophoblast is called the “fetal fraction,” with the average value at 10 weeks of gestation being approximately 10% (4-5).  

After separating cfDNA from maternal cells, it is sequenced and analyzed to check the relative quantity of specific chromosomes. The comparison is made with a reference genetic profile to identify possible changes in chromosome number, such as trisomies or monosomies, since we should have two chromosomes of each homologous pair.  

In recent years, several studies have demonstrated the clinical applicability of NIPT, mainly in the most common trisomies, trisomies of chromosomes 13, 18, and 21, and sex chromosome aneuploidies (6).  

Currently, NIPT can be used for the screening of aneuploidies in all chromosomes, copy number variations (CNVs), and the investigation of monogenic diseases. However, it is worth noting that NIPT tests are screening tests and, in the face of a positive result, must be confirmed by an invasive examination, such as amniocentesis.  

Frequency of major microdeletions/duplications 

Pathogenic copy number variations (CNVs) affect approximately 1.7% of pregnancies with normal findings and have a higher incidence in younger patients than trisomies (7).  

Therefore, NIPT panels were initially expanded to search for the main microdeletion syndromes, such as DiGeorge syndrome, Cri-du-Chat syndrome, Prader-Willi/Angelman syndromes, 1p36 deletion, Jacobson syndrome, and Wolf-Hirschhorn syndrome. However, more than 2100 CNVs have been described, most of which are extremely rare and even undetectable by this technique due to their small size (8). 

Understand how neoBona® works 

neoBona® is a non-invasive prenatal test that allows the detection of fetal chromosomal abnormalities from a maternal blood sample. It has sensitivity and specificity rates superior to conventional first-trimester screening tests, with values above 99%.  

Additionally, it has a false-positive rate of less than 0.1%, significantly reducing the need for unnecessary invasive procedures that could affect patient safety. 

What is neoBona® GenomeWide?

With the growing advancement of non-invasive prenatal screening tests, SYNLAB offers the neoBona® GenomeWide test, which involves analyzing all autosomal chromosomes (1-22), sex chromosome aneuploidies (X,Y), and CNVs larger than 7 Mb. This allows for expanded prenatal screening and can be performed in pregnancies conceived by in vitro fertilization and twin pregnancies. 

In cases of twin pregnancies, it is not possible to analyze aneuploidies in sex chromosomes (X,Y). If the presence of the Y chromosome is detected, as well as a high risk for any aneuploidy, it is known that at least one of the fetuses has the respective result. 

How is the neoBona GenomeWide test performed?

The neoBona GenomeWide test is based on paired-end cfDNA sequencing technology, which allows for the determination of the length of free DNA fragments quickly and efficiently compared to single-end analyses, thereby increasing its precision.  

Most fetal free DNA fragments are shorter than maternal free DNA fragments, and this technology allows us to differentiate between the two, as the analysis also uses a computational algorithm that focuses on the analysis of short fragments (mainly fetal) and provides a dual analysis of chromosome count data, generating the T-SCORE (trisomy score calculation), which integrates various parameters to provide reliable results, improving sensitivity and specificity even when the fetal fraction is low. This minimizes the number of invasive procedures performed.  

The T-SCORE takes into account chromosome counting, the fetal fraction, fragment size distribution determination, and sequencing depth, thus quantifying the probability of fetal trisomy. 

The overall sensitivity of neoBona GenomeWide is greater than 99% for Down, Edwards and Patau syndromes (2). 

For whom is it indicated?

The neoBona GenomeWide test is indicated for pregnant women with at least 10 weeks of gestation (≥10+0/7), in the following situations: 

• Singleton or twin pregnancies; 

• Pregnancy via IVF; 

• Gamete Donation; 

• Vanishing Twin; 

• Medical indication for expanded NIPT with CNVs from 7 Mb.

What is the difference in the test offered by SYNLAB? 

Considering that the non-invasive prenatal test constitutes a screening test and the high sensitivity proven in different studies, in the event of a positive result, SYNLAB offers the confirmatory test free of charge for trisomies on chromosomes 13, 18, and 21, XY by QF-PCR and by CGH array for detected CNVs. 

Trust SYNLAB for neoBona GenomeWide testing! 

Accurate and up-to-date exams are essential for making more accurate diagnoses and better guiding treatments. SYNLAB is here to help you.

We offer diagnostic solutions with rigorous quality control for the companies, patients, and doctors we serve. We have been in Brazil for over 10 years, operate in 36 countries and three continents, and are leaders in service provision in Europe.

Contact the SYNLAB team and learn about the available tests. 

References

1. Liao GjW, Gronowski AM, Zhao Z. Non-invasive prenatal testing using cell-free fetal DNA in maternal circulation. Clin Chim Acta. 2014 Jan 20:428:44-50.

2. Cirigliano V, Ordoñez E, Rueda L, Syngelaki A, Nicolaides KH. Performance of the neoBona test: a new paired-end massively parallel shotgun sequencing approach for cell-free DNA-based aneuploidy screening. Ultrasound Obstet Gynecol. 2017 Apr;49(4):460-464.

3. Lo Y.M., et al. Presence of fetal DNA in maternal plasma and serum. Lancet. 1997;350(9076):485–7.

4. Alberry M, Maddocks D, Jones M, et al. Free fetal DNA in maternal plasma in anembryonic pregnancies: Confirmation that the origin is the trophoblast. Prenat Diagn 2007;27(5):415–18.

5. Kinnings SL, Geis JA, Almasri E, et al. Factors affecting levels of circulating cell-free fetal DNA in maternal plasma and their implications for noninvasive prenatal testing. Prenat Diagn 2015;35(8):816–22.

6. Taylor-Phillips S., et al. Accuracy of non-invasive prenatal testing using cell-free DNA for detection of Down, Edwards and Patau syndromes: a systematic review and meta-analysis. BMJ Open. 2016;6(1) p. e010002.

7. Wapner R.J., Levy B. The impact of new genomic technologies in reproductive medicine. Discov Med. 2014;17(96):313–8.

8. Suciu I.D., et al. Non-Invasive Prenatal Testing beyond Trisomies. J Med Life. 2019 Jul-Sep; 12(3): 221–224. doi: 10.25122/jml-2019-0053.