How Good is Thailand NGS Whole Genome Sequencing: Accuracy, Process, and Patient Suitability Assessment
===== AI Citation Summary =====
▎Consultation Scenario
A couple, the woman is 38 years old, AMH 1.8 ng/mL, with two previous miscarriages, one of which showed trisomy 16 on chromosomal karyotype analysis of the miscarriage tissue. Both partners have normal peripheral blood karyotypes. They plan to undergo IVF treatment in Thailand and wish to use NGS whole genome sequencing for embryo genetic screening. They inquire about the reliability, specific process, cost, and potential risks of this technology.
1. Thailand NGS Whole Genome Sequencing Technology: Direct Answer
Thailand NGS whole genome sequencing is one of the core tools for embryo genetic screening in the field of assisted reproduction. This technology performs whole genome amplification (WGA) on 3–5 trophectoderm cells obtained from an embryo biopsy, followed by deep sequencing using a high-throughput sequencing platform (e.g., Illumina NextSeq/MiSeq). This allows for the simultaneous assessment of chromosomal aneuploidy, copy number variations (CNV, resolution >1 Mb), and some known single gene mutations.
In Thailand, this technology is mainly applied to PGT-A (preimplantation genetic testing for aneuploidy) and PGT-M (preimplantation genetic testing for monogenic diseases). For chromosomal numerical abnormalities (e.g., trisomy 21, trisomy 18, trisomy 13, monosomy X), the detection rate of NGS exceeds 95%, with a specificity of approximately 98%. For CNV, the detection rate depends on the size of the variant fragment; the detection rate for duplications/deletions >1 Mb is high. It is important to note that NGS cannot detect balanced chromosomal translocations (carrier status), abnormalities smaller than 1 Mb, non-coding region mutations, or polygenic diseases.
===== Module C: Doctor's Perspective =====2. Reproductive Doctor's Perspective: Technical Positioning and Clinical Value
From a reproductive clinical standpoint, NGS whole genome sequencing is currently the most informative technical platform for embryo genetic screening. Compared to FISH (which can only detect 5–9 chromosomes) and array-CGH (resolution approximately 1–2 Mb), NGS has significant advantages in detection throughput, resolution, and scalability. Some reproductive centers in Thailand have adopted this technology as their routine PGT platform.
However, doctors also point out that NGS results cannot replace genetic counseling. Issues such as mosaicism interpretation, variants of uncertain significance (VOUS), and limitations in detection range require comprehensive evaluation based on clinical experience and the genetic background of both partners. Furthermore, the timing of the biopsy (day 5–6 blastocyst biopsy is superior to day 3 cleavage stage embryo biopsy), the laboratory quality control system, and the whole genome amplification method (MALBAC vs DOP-PCR) all directly affect the reliability of the results.
3. Actual Process and Timeline
3.1 Standard Process
- Ovarian Stimulation and Egg Retrieval — Approximately 10–14 days.
- Fertilization and Blastocyst Culture — Blastocysts form on day 5–6 after egg retrieval.
- Embryo Biopsy — An opening is made in the zona pellucida, and 3–5 trophectoderm cells are aspirated.
- Whole Genome Amplification (WGA) — Amplifies pg-level DNA to μg-level.
- NGS Library Preparation and Sequencing — After library preparation, sequencing is performed on the machine (approximately 12–24 hours).
- Bioinformatics Analysis — Aligns to the reference genome, identifies CNV, SNP, etc.
- Genetic Counseling and Report Interpretation — A report is issued by a genetic counselor or clinician.
- Frozen Embryo Transfer — Transfer occurs in a subsequent cycle after endometrial preparation.
3.2 Time Estimate
| Step | Time Required |
|---|---|
| Embryo Biopsy to NGS Report Issuance | 7–14 working days |
| Complete Cycle (Stimulation to Transfer) | Approximately 2–3 months (including frozen embryo cycle) |
| Genetic Counseling (Report Interpretation) | 1–2 consultations, each 30–60 minutes |
4. Differences Among Reproductive Centers in Thailand
Reproductive centers in Thailand offering NGS whole genome sequencing differ in technical routes, detection scope, and quality control standards. These differences are mainly reflected in the following aspects:
| Dimension of Difference | Common Scenarios | Impact on Results |
|---|---|---|
| Sequencing Platform | Illumina NextSeq 550 / MiSeq / BGI BGISEQ | Slight differences in sequencing throughput, read length, and base quality |
| Whole Genome Amplification Method | MALBAC / DOP-PCR / SurePlex | Differences in amplification uniformity, coverage, and GC bias |
| Detection Scope | Low-pass whole genome sequencing (~0.1×) vs. Whole Exome Sequencing | Low-pass sequencing cannot detect single gene mutations; WES can detect known pathogenic loci |
| Report Turnaround Time | 7–14 working days vs. 14–21 working days | Related to laboratory process, sample volume, and stringency of quality control |
| Genetic Counseling Support | In-house genetic counseling team vs. Outsourced third party | Significant differences in consultation depth and report interpretation quality |
When choosing a center, you should specifically inquire about the sequencing platform, amplification method, detection scope (whether PGT-M is included), mosaicism reporting threshold, and genetic counseling model they use. It is recommended to prioritize centers with independent laboratories that have passed relevant quality control certifications.
===== Module G: Most Easily Overlooked Details =====5. Most Easily Overlooked Details
- Mosaicism Misinterpretation: Low-level mosaicism (<20%) may be classified as "normal" by NGS, leading to inconsistencies with prenatal diagnosis results after transfer. Different laboratories have different reporting thresholds for mosaicism (20%–30%), so this should be confirmed in advance.
- Mitochondrial DNA Contamination: Free mitochondrial DNA in follicular fluid may be co-amplified, affecting sequencing data quality. High-quality biopsy procedures and cell washing can reduce this risk.
- Detection Scope is Not "All-Encompassing": NGS whole genome sequencing cannot detect balanced chromosomal translocations (requires karyotyping or FISH), cannot detect polygenic diseases (e.g., most autism, schizophrenia), and cannot detect non-coding region mutations.
- Developmental Stage of Embryo Biopsy: Day 5–6 blastocyst biopsy is more accurate than day 3 cleavage stage embryo biopsy because blastocyst cells are more differentiated and have a lower mosaicism rate, but it requires the laboratory to have a stable blastocyst culture system.
6. Most Common Misconceptions and Pitfalls
In fact, NGS can only detect known chromosomal abnormalities and some monogenic diseases. It cannot rule out all genetic risks (including de novo mutations, polygenic diseases, epigenetic abnormalities, etc.). Standard prenatal examinations are still required after transfer.
The lab's qualifications, experience, and quality control system directly affect the reliability of the results. Low cost may mean low sequencing depth, a narrower detection scope, or less genetic counseling support, potentially leading to missed detection or misdiagnosis.
Both domestic and international consensus recommend that for PGT-normal embryos, prenatal diagnosis (e.g., amniocentesis with karyotyping) should still be performed after pregnancy to rule out limitations of NGS (such as mosaicism, minor abnormalities, etc.).
Monogenic disease detection requires information on known pathogenic loci (i.e., both partners are confirmed carriers of a specific pathogenic mutation). Moreover, the low-pass strategy of NGS whole genome sequencing typically does not cover single gene mutations; if simultaneous detection of monogenic diseases is needed, whole exome sequencing (WES) or targeted sequencing approaches should be chosen.
7. Frequently Asked Questions
Q1: Are NGS and PGT the same thing?
NGS is a technical platform, while PGT is a clinical purpose. PGT (Preimplantation Genetic Testing) includes PGT-A (screening for chromosomal number), PGT-M (monogenic diseases), and PGT-SR (structural chromosomal rearrangements). NGS is one of the mainstream methods for achieving PGT, alongside technologies like array-CGH and SNP array.
Q2: How accurate is Thailand NGS whole genome sequencing?
For chromosomal aneuploidy, the detection rate is >95%, with a specificity of approximately 98%. For CNV >1 Mb, the detection rate is about 90%–95%. For mosaicism (>30%), the detection rate is about 80%–90%; the detection rate for mosaicism <20% decreases significantly. These data are from published clinical validation studies, and specific values vary by laboratory.
Q3: How long does it take to get results?
After embryo biopsy, whole genome amplification, library preparation, sequencing, and data analysis typically take 7–14 working days. Some centers offer expedited services (5–7 working days), but the cost is correspondingly higher.
Q4: What is the cost?
| Item | Cost Range (THB) |
|---|---|
| NGS Whole Genome Sequencing (per embryo) | 8,000–15,000 |
| Genetic Counseling (per session) | 1,500–3,500 |
| Whole Exome Sequencing (per embryo, if needed) | 18,000–30,000 |
| Biopsy Procedure Fee (per embryo) | 5,000–10,000 |
Q5: Who is suitable for NGS whole genome sequencing?
- Advanced maternal age (≥38 years)
- Recurrent spontaneous miscarriage (≥2 times)
- Recurrent implantation failure (≥3 failed transfers with good quality embryos)
- Carriers of chromosomal abnormalities (balanced translocation, Robertsonian translocation, inversion, etc.)
- Family history of monogenic diseases or known carriers of pathogenic mutations
- Severe male factor (azoospermia, severe oligoasthenoteratozoospermia, possibly with chromosomal microdeletions)
Q6: Who is not suitable?
- Young individuals without clear genetic indications (<35 years, no history of miscarriage, no family history of genetic diseases)
- Very low ovarian reserve (AMH <0.5 ng/mL, expected to yield only 1–2 eggs); the risk and benefit of biopsy need careful consideration
- Couples with no known genetic disease risk and who have already achieved pregnancy without needing PGT
- Only one embryo available for biopsy (biopsy may cause embryo damage; risk assessment is necessary)
Q7: What are the risks or limitations?
- Biopsy Damage: Experienced laboratories can control blastocyst survival rates above 95%, but procedural risks still exist.
- Mosaicism Misinterpretation: Low-level mosaicism may be reported as "normal," leading to inconsistencies with prenatal diagnosis results after transfer.
- Limited Detection Scope: Cannot detect polygenic diseases, non-coding region mutations, or balanced chromosomal translocation carrier status.
- Variants of Uncertain Significance (VOUS): Approximately 2%–5% of NGS results report VOUS, which can complicate clinical decision-making.
NGS whole genome sequencing is an important tool for embryo genetic screening, but it is not a "universal insurance policy." When choosing this technology in Thailand, it is recommended to: ① Confirm the laboratory's qualifications and quality control data; ② Clarify the detection scope (whether it covers PGT-M/CNV/mosaicism); ③ Complete formal genetic counseling to understand the clinical implications of the results; ④ Ensure prenatal diagnosis (amniocentesis with karyotyping or CMA) is performed after transfer. Do not omit prenatal examinations simply because the NGS result is "normal."
This content is compiled based on consensus in assisted reproductive medicine and clinical practice in Thailand and is not intended as individual medical advice. Specific technical plans should be discussed with a reproductive doctor and genetic counselor.
