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NIPT(NGS) Testing Services

Definition and Overview

Non-Invasive Prenatal Testing (NIPT) is a revolutionary prenatal screening technology. It uses next-generation sequencing (NGS) technology to deeply sequence and analyze cell-free DNA (cfDNA) in maternal plasma, thereby providing a high-precision prenatal screening method for assessing the risk of common chromosomal aneuploidies in the fetus.

Compared to traditional invasive prenatal diagnostic techniques (such as amniocentesis and chorionic villus sampling), NIPT requires only 10 mL of maternal venous blood, completely avoiding the risks of intrauterine infection and miscarriage associated with the procedure (with a risk of approximately 0.5-1%). Therefore, it is more easily accepted by pregnant women and offers significant advantages such as being non-invasive, safe, and with zero miscarriage risk. It has become a widely used first-line prenatal screening option worldwide.

Working Principle

The scientific basis of NIPT stems from a significant discovery in 1997: the presence of fetal-derived cell-free DNA (cfDNA) in maternal peripheral blood. This DNA, primarily derived from placental trophoblasts, is cleared from the maternal blood within hours after delivery. cfDNA is detectable after 5 weeks of gestation and increases with gestational age. By 12 weeks of gestation, cfDNA typically accounts for over 10% of the total maternal cfDNA, meeting the requirements for high-precision NIPT testing.

The technology is primarily based on massively parallel genomic sequencing (MGS).

The core working principles are as follows:

1. DNA extraction and library construction: Plasma is isolated from maternal venous blood samples, from which total cfDNA (containing both maternal and fetal cell-free DNA fragments) is extracted and a sequencing library is constructed.

2. High-throughput sequencing (NGS): The extracted DNA is sequenced in massive parallel fashion using NGS technology, generating tens of millions of short DNA reads.

3. Bioinformatics Analysis: The measured sequences are compared with the human reference genome to precisely locate the chromosome to which each sequence belongs.

4. Statistical Algorithms and Risk Assessment: Advanced bioinformatics algorithms are used to calculate the percentage of sequence reads for each chromosome. In a normal diploid fetus, the percentage of reads for each chromosome is relatively constant. If the fetus has a chromosomal abnormality (such as trisomy 21 in Down syndrome), the percentage of sequence reads corresponding to that chromosome will significantly deviate from the normal threshold. Using complex statistical algorithms (such as the Z-score test), the computer can determine whether there is a dosage deviation for that chromosome and thus calculate the fetal risk of disease.

Workflow

Our NIPT testing service follows a rigorous, standardized operating procedure to ensure the accuracy and reliability of the results.

Clinical Consultation and Informed Consent

Professionals will provide the client with a detailed explanation of the test content, advantages, limitations, and applicable scope, and the client will sign a fully informed consent form.

Sample Collection and Transportation

After 12 weeks of gestation, 10 mL of peripheral blood will be collected from the mother using a dedicated blood collection tube. The special protective agent in this tube effectively protects the stability of the cfDNA. Samples are transported to a certified testing laboratory under cold chain conditions.

Laboratory Testing

* Plasma Separation and DNA Extraction: Double centrifugation in a high-speed centrifuge separates plasma components and purifies total cfDNA from them.

* Library Construction and Sequencing: End-repair and adapter addition are performed on the cfDNA fragments to construct libraries suitable for NGS sequencing, which are then processed on a high-throughput sequencing instrument.

* Data Analysis and Report Generation: Our proprietary bioinformatics analysis pipeline processes, aligns, and calculates the massive sequencing data to generate chromosome dose risk values. Experienced genetic analysts review both the data quality (e.g., fetal DNA concentration) and the results.

* Report Issuance and Genetic Counseling: Within 5-7 business days of receiving qualified samples, the laboratory will issue a clear, easy-to-understand official test report clearly indicating the risk level (high or low) for the target disease (e.g., T21, T18, T13). Our partner genetic counselors or clinicians will interpret the report based on the results and provide professional follow-up advice and consulting services. For high-risk results, invasive prenatal diagnosis is usually recommended for definitive diagnosis.

Technical Advantages

Ultra-High Accuracy

The detection rate for trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome) (>99%) is significantly higher than traditional Down syndrome screening (approximately 70-90%), while significantly reducing the false-positive rate to below 0.1%.

Extremely High Safety

Requiring only venous blood draw from the mother, this method avoids the risks of intrauterine infection and miscarriage (approximately 0.5-1%) associated with chorionic villus sampling or amniocentesis, leading to high acceptance among pregnant women.

Wide Detection Coverage

In addition to autosomal trisomal trisomy, high-end NIPT services also offer screening options for sex chromosome aneuploidies (such as Turner syndrome and Klinefelter syndrome) and various chromosomal microdeletion/microduplication syndromes.

Early Gestational Testing

Testing can be performed as early as 10 weeks of gestation, providing timely results and ample time for subsequent decision-making.

Clear and Reliable Results

Based on digital quantitative analysis using NGS, results are objective, effectively reducing uncertainty caused by fluctuations in serological indicators.

High Throughput and High Degree of Automation

NGS technology enables simultaneous testing of large numbers of samples, resulting in high efficiency.

Application Scenarios and Applicable Populations

Common Aneuploidy Screening: This is the core application of NIPT, primarily used to screen for trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome), with accuracy rates exceeding 99%.

Screening for sex chromosome aneuploidies: such as Turner syndrome (45, X) and Klinefelter syndrome (47, XXY).

Fetal sex determination: By analyzing the presence or absence of sequences on the Y chromosome, fetal sex can be determined early, which is important for risk assessment of sex-linked genetic diseases.

Microdeletion/microduplication syndrome screening: Some enhanced NIPT products can screen for diseases caused by small chromosomal deletions or duplications, such as DiGeorge syndrome (22q11.2 deletion).

NIPT is suitable for all pregnant women who wish to rule out common chromosomal risks to the fetus and is particularly recommended for the following:

*Advanced pregnant women (age ≥35 years at delivery).
*Pregnant women whose serological screening results indicate high or borderline risk.
*Pregnant women with abnormal soft ultrasound markers (such as increased NT) who do not wish to undergo invasive prenatal diagnosis.
*Pregnant women with a history of chromosomal abnormalities or a family history of such a fetus.
*Pregnant women who have undergone IVF or multiple miscarriages. Pregnant women of average gestational age who demand higher precision and peace of mind from prenatal screening.

Important Note: NIPT is a high-precision screening technique, not a definitive diagnosis. Despite its high accuracy, any screening test carries a very small risk of false positives and false negatives. Therefore, high-risk NIPT results must be confirmed by invasive prenatal diagnostic techniques such as amniocentesis.

NGS-based NIPT technology is a milestone in prenatal screening. It successfully integrates genomics with clinical medicine, providing prospective parents with unprecedented and powerful information from a simple blood sample, significantly advancing the prevention and treatment of birth defects. However, it is crucial to correctly understand its role as an "advanced screening" technique. It should be integrated with professional genetic counseling as a key component of prenatal care, helping families make informed reproductive choices and welcome healthy newborns.

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