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Summary of This Article
NIPT (Non-Invasive Prenatal Testing) is a safe and effective method for accurately detecting chromosomal abnormalities in the fetus. However, there are cases where the test results become inconclusive. At Hiro Clinic as well, a certain number of inconclusive cases have been reported. In the following, we explain in detail the proportion, causes, and countermeasures of such inconclusive cases.
Proportion of Inconclusive Cases
Hiro Clinic has not publicly released specific data regarding the percentage of inconclusive results (also known as “no-call” results) in their NIPT (Non-Invasive Prenatal Testing). However, on a broader scale, inconclusive results generally occur in about 1% to 5% of all tests. This percentage can vary depending on the testing method, the technology used, and the testing laboratory. It is assumed that the proportion at Hiro Clinic falls within this range as well.
Main Causes of Inconclusive Results
1. Maternal Mosaicism
Maternal mosaicism refers to a condition in which different genetic cell lines coexist in the mother’s blood. This mixture of maternal DNA and fetal DNA can blur the genetic signals analyzed during testing, making it difficult to generate a clear result. This is considered one of the primary causes of inconclusive outcomes.
2. Maternal Physiological Variations
Certain physiological or hematological conditions in the mother, such as elevated white blood cell counts or coagulation abnormalities, may interfere with the sequencing process. These irregularities can complicate the interpretation of the DNA fragments and increase the chance of receiving an inconclusive result.
3. Sample Quality Issues
If the blood sample collected is of poor quality — for example, if the volume is insufficient or the sample degrades during storage or transport — the DNA may not be suitable for accurate analysis, leading to a no-call result.
Retesting and Alternative Approaches
Many patients, upon receiving an inconclusive result, opt for a second blood draw. However, if the underlying cause is maternal mosaicism or a physiological condition, repeating the blood test often yields the same inconclusive result. Hiro Clinic recommends the following strategies in such situations:
1. Amniocentesis
When the NIPT result is inconclusive, amniocentesis is considered the most reliable follow-up test. This procedure analyzes cells that come directly from the fetus, eliminating interference from maternal DNA and providing a highly accurate result.
That said, amniocentesis is an invasive procedure and carries certain risks, so it requires careful explanation, patient understanding, and informed consent before proceeding.
2. Detailed Explanation and Genetic Counseling
Hiro Clinic offers thorough explanations to patients about the reasons for the inconclusive result. Genetic counseling is emphasized to help patients understand that retesting is not always the best solution. During counseling, the potential influence of maternal mosaicism or physiological variations is clarified, and suitable testing options are discussed.
3. Collaboration with Testing Laboratories
Hiro Clinic works closely with partner laboratories to investigate the specific causes of inconclusive results. This collaboration helps refine testing processes and is expected to reduce the frequency of inconclusive cases over time.
Explanation and Response Strategy
At Hiro Clinic, a small proportion of NIPT tests result in inconclusive findings. This is most often due to maternal mosaicism or physiological factors that interfere with the analysis. When this happens, simply repeating the blood draw typically does not solve the problem. Instead, amniocentesis is recommended because it directly evaluates fetal cells, ensuring higher accuracy.
The clinic provides clear and detailed explanations about the testing process, the associated risks, and the benefits of each option. In parallel, Hiro Clinic continues to strengthen its collaboration with testing facilities, analyzing the underlying factors in each case to minimize future occurrences.
Research and Evidence
Current research shows that inconclusive NIPT results are primarily caused by mixed maternal-fetal DNA signals during sequencing. Advances in laboratory techniques and analytical processes are expected to enhance detection accuracy. Hiro Clinic is actively working to integrate these advancements to make testing more reliable and efficient.
Summary
At Hiro Clinic, inconclusive NIPT results occur in approximately 1% to 5% of cases, mainly due to maternal mosaicism, maternal physiological conditions, or issues with sample quality. Retesting with a second blood draw is not always effective in resolving these issues. In such situations, amniocentesis is often recommended for more accurate results.
By providing comprehensive explanations, offering genetic counseling, and strengthening collaboration with laboratories, Hiro Clinic aims to both improve patient understanding and reduce the occurrence of inconclusive results. For patients, being well-informed and maintaining open communication with their healthcare providers helps ensure that they choose the most appropriate and reliable testing approach.
