Analysis of Embryo Genetic Testing Accuracy in Thailand: Reproductive Specialist Interprets PGT Technology Clinical Data

Opening: Physician Decision Logic

In reproductive medicine clinics, whether to perform genetic testing before embryo transfer and how to interpret test reports are issues that require careful consideration in clinical decision-making. For patients choosing to undergo embryo genetic testing (PGT) in Thailand, I am frequently asked the same question: How accurate is embryo genetic testing in Thailand? This question seems simple on the surface, but answering it requires elaboration from four dimensions: technical principles, laboratory conditions, embryo biological characteristics, and clinical interpretation. Based on clinical data and industry consensus, this article systematically addresses this core question.

I. Accuracy of Embryo Genetic Testing in Thailand: Direct Answer

Reproductive centers in Thailand currently widely use embryo genetic testing technology, with an accuracy of approximately 95% to 99% for screening chromosomal numerical abnormalities (aneuploidy), including a sensitivity of about 95% and specificity of about 98%. However, this data needs to be understood in the context of the type of test:

• PGT-A (Aneuploidy Screening): High detection rate for whole chromosome numerical abnormalities, with a false positive rate of about 2% to 5% and a false negative rate of about 1% to 3%.
• PGT-M (Monogenic Disease Testing): Requires family linkage analysis or direct mutation detection, with accuracy reaching over 99%, provided family samples are complete and the inheritance pattern is clear.
• PGT-SR (Structural Rearrangement Testing): Accuracy ranges between PGT-A and PGT-M, approximately 95% to 98%, depending on breakpoint locations and the resolution of the detection platform.

PGT laboratories in Thailand commonly use Next-Generation Sequencing (NGS) platforms, which are technically on par with those in Europe, America, and Japan. However, differences exist among reproductive centers in biopsy experience, quality control systems, and embryo culture conditions, which directly affect the final testing accuracy.

II. Interpretation of Core Indicators: Sensitivity, Specificity, and Predictive Value

Evaluating the accuracy of a testing technology cannot rely solely on a single "accuracy" number. The following three indicators are crucial in PGT reports:

The above values are based on published data from mainstream reproductive centers in Thailand. In practice, the positive predictive value is influenced by patient age and embryo grade — older women have higher rates of embryonic aneuploidy, which increases the positive predictive value.

III. Most Easily Overlooked Details: Mosaicism, Biopsy Techniques, and Laboratory Differences

In clinical practice, I find that patients and some junior practitioners often overlook three key details that directly determine the reliability of test results.

3.1 Embryo Mosaicism

During early development, an embryo may have some cells with normal chromosomes and others with abnormal ones, a condition known as mosaicism. If the biopsied trophectoderm cells happen to be from the normal or abnormal part, the report will not match the actual embryo status. The incidence of mosaicism is about 5% to 20%, making it a major cause of false positives or false negatives in PGT. Currently, Thai laboratories typically classify mosaicism by proportion:

• Low-level mosaicism (20%–40%) — clinical significance remains controversial
• High-level mosaicism (>40%) — usually considered abnormal
• Uniform abnormality — entire chromosome completely abnormal

Clinical management of mosaic embryos requires individualized decision-making and is not simply "usable" or "not usable."

3.2 Biopsy Method and Timing

Most reproductive centers in Thailand use Day 5 or Day 6 trophectoderm biopsy (taking 5–8 cells). Compared to Day 3 cleavage-stage biopsy (taking only 1 cell), this method provides more cells, better representation, and higher accuracy. However, the potential impact of the biopsy procedure on the embryo and the tolerance of the embryo to freezing and thawing after biopsy also need to be considered.

3.3 Laboratory Quality Control Systems

Differences exist among laboratories in the following areas:

• Proficiency and consistency of biopsy procedures
• Uniformity of DNA amplification
• Sequencing depth and coverage
• Threshold settings for mosaicism interpretation
• Indications for repeat testing

When selecting a laboratory, attention should be paid to whether it participates in external quality control programs and has published clinical data, rather than relying solely on promotional claims.

IV. Most Common Pitfalls: Common Misconceptions in Report Interpretation

In clinical consultations, I have observed the following four common errors in report interpretation that can lead to biased transfer decisions:

• Misconception 1: Believing that a normal PGT result means the embryo is 100% healthy. PGT only screens for chromosomal number and some structural abnormalities; it cannot detect microdeletions, microduplications (below the detection resolution), mitochondrial diseases, or polygenic disorders.
• Misconception 2: Believing that an abnormal PGT result means the embryo is completely untransferable. Mosaic embryos (low-level mosaicism, specific chromosomes) may still be transferred and result in healthy births in some cases, requiring evaluation by both a genetic counselor and a reproductive specialist.
• Misconception 3: Ignoring the limitations of the testing platform. Different NGS platforms have varying sensitivity and resolution for mosaicism; some platforms may miss low-level mosaicism.
• Misconception 4: Equating PGT results with prenatal diagnosis. After any PGT pregnancy, prenatal diagnosis (amniocentesis or chorionic villus sampling) is mandatory to confirm the true fetal status.

V. Differences in PGT Technology: Thailand vs. the United States and Mainland China

Is PGT technology in Thailand more accurate than in mainland China or the United States? This is a common question from patients. From a technical platform perspective, differences are no longer significant, but distinctions exist in the following three areas:

Overall, Thailand has accumulated extensive experience in the PGT field with mature technical application. However, the testing level in top-tier reproductive centers in mainland China is now very close. The choice of where to undergo PGT depends more on the integration of the overall treatment plan, scheduling, and logistical factors such as whether embryo transport is needed.

VI. Special Situation Management: Mosaic Embryos and Repeat Testing

Clinical decision-making for the following three special situations requires extra caution:

• Transfer decision for mosaic embryos: For low-level mosaicism (<40%) involving autosomal aneuploidy, some centers recommend re-biopsy or prenatal diagnosis after transfer. No unified guidelines currently exist; thorough communication between physician and patient is necessary.
• Inconsistent test results: If test results for two embryos clearly contradict their morphological grading (e.g., a morphologically good embryo reported as abnormal, while a poor one is normal), it is advisable to communicate with the laboratory about re-analysis or re-biopsy.
• Recurrent PGT abnormalities: If multiple embryos all show chromosomal abnormalities, it is necessary to investigate whether the parents carry cryptic translocations or mosaicism, potentially requiring high-resolution peripheral blood karyotyping or sperm FISH testing.

VII. Physician's Perspective: Clinical Positioning of PGT Accuracy

As a reproductive specialist, I believe PGT is an effective embryo screening tool, but not a precise diagnostic tool. The 95%–99% accuracy figure clinically means:

• For older women (≥38 years), PGT can significantly reduce the risk of transferring aneuploid embryos and improve the implantation rate per single transfer.
• For patients with recurrent implantation failure or recurrent miscarriage, PGT helps select chromosomally normal embryos but cannot resolve all implantation issues.
• For couples carrying monogenic diseases, PGT-M is currently the most effective means to block disease transmission, with accuracy approaching 99%.
• For young patients with normal ovarian function, the benefit of PGT is relatively limited, as their baseline embryonic aneuploidy rate is low, and there is a risk of discarding embryos due to false positives.

In clinical decision-making, I usually advise patients to view PGT as a "risk stratification tool" rather than an "absolute guarantee." Even after transferring a PGT-normal embryo, there remains approximately a 1%–3% risk of chromosomal abnormality (false negative or embryonic self-correction), which is an objective fact patients need to understand.

VIII. Practitioner Observations: The Real State of the PGT Industry in Thailand

Over the past 8 years, I have engaged in academic exchanges or case discussions with laboratory teams from six reproductive centers in Thailand. Here are some real observations:

• The hardware facilities (sequences, incubators, micromanipulators) in Thai PGT laboratories generally meet international standards, with some centers even equipped with the latest long-read sequencing platforms for research.
• The stability of laboratory personnel is a key factor affecting testing quality. Centers with lower technician turnover show significantly better biopsy success rates and testing reproducibility.
• Thai laboratories vary in sensitivity for detecting mosaicism: some can reliably detect mosaicism above 20%, while others have poorer consistency in interpreting low-level mosaicism.
• Many Thai centers have long-term embryo transport collaborations with reproductive centers in China, Southeast Asia, and Australia, possessing extensive experience in embryo freezing, transport, and thawing, which helps ensure post-test embryo survival.
• Communication costs due to language barriers and time differences are real. It is advisable for patients to choose centers with Chinese coordinators or established collaboration channels with domestic institutions to minimize information loss.

IX. Physician's Advice: How to Rationally View Embryo Genetic Testing in Thailand

Based on the above analysis, I offer the following five suggestions:

• Clarify the testing purpose: Is it for screening aneuploidy (PGT-A), blocking monogenic diseases (PGT-M), or detecting structural rearrangements (PGT-SR)? Different purposes involve different strategies and accuracy levels.
• Request laboratory quality control data: Ask the center to provide data from the past 1–2 years on biopsy success rates, amplification failure rates, mosaicism detection rates, and post-transfer clinical outcomes, rather than relying solely on verbal descriptions.
• Set realistic expectations: After transferring a PGT-normal embryo, the clinical pregnancy rate is still about 40%–50% (depending on age and embryo quality), not 100% success. High testing accuracy does not equate to high transfer success.
• Keep raw data: Request a detailed test report from the laboratory, including an analysis summary of raw sequencing data, mosaicism percentage, testing platform, and coverage information, to allow for secondary analysis or consultation if needed.
• Mandatory prenatal diagnosis after transfer: Regardless of the PGT result, amniocentesis or chorionic villus sampling should be performed after pregnancy, as this is the only gold standard for confirming fetal chromosomal status.

Embryo genetic testing technology in Thailand is generally at an upper-intermediate international level, with reliable accuracy, but inter-laboratory variability and inherent limitations of the testing technology exist. As a clinician, my role is to help patients understand the meaning behind these numbers and make truly informed choices — rather than blindly pursuing a specific test indicator.