Article written by Dr. Bui Thi Phuong Hoa – Genetic Consultant – Share99 High-Tech Center
A pre-birth diagnosis of chroma abnormalities has been made since mid-1960. Mainly in the last 60 years, fetal cellular testing has been carried out using the standard G-band dyeing karyotyping method. The effectiveness of diagnosis using ordinary cellular analysis by karyotype depends on the indication. For the most common indications such as high mive age and positive bio-screening, the diagnostic effect with a spike biopy and amniotic puncture is about 6% and 3%, respectively.
1. Advantages of the CMA in pre-birth diagnosis
The advent of newer molecular cellular technologies such as chroma microarray analysis (CMA) offers the prospect of making a diagnosis at a higher resolution. The CMA, which detects imbalances in the Kb range, easily demonstrates its superiority over culture cell analysis, limited to imbalances greater than 7-10Mb.
In post-birth studies in children with congenital abnormalities, developmental delays or intellectual disabilities, the CMA will have additional diagnosis of smaller clinically related chromic abnormalities of approximately 12 to 15%.
2. CMA Sensitivity
As with any clinical test, cma sensitivity depends on the quality of the sample and DNA. Each CMA platform is limited by the resolution of the probe coverage (the number of probes, their location as well as their distance).
Therefore, variations that fall into areas with low probe coverage or without probes may be ignored. In fact, most clinical laboratories that apply array techniques will optimize the coverage of probes for areas of chromosity of clinical significance that are associated with genetic disorders or known disease syndromes.
From a consultation perspective, patients should be informed that microarray analysis cannot detect all genetic changes, and normal CMA results do not reduce the risk of other genetic diseases or birth defects.
Types of genetic changes that cannot be detected pre-birth by CMA include paragraph transitions, paragraph reversals, balanced segment insertion, and point mutations. Additionally, triads cannot be detected by aCGH because additional copies of all chromochromos are masked by the standardization process run by software analysis.
3. Pre-test genetic counseling
Since this is a complex test, patients need genetic counseling before taking the test. Pre-testing counseling informs patients about the benefits and limitations of testing, thereby helping patients make informed decisions regarding the suitability of the test based on their beliefs and personal attitudes.
Customers can go directly to Share99 Times City for a visit or contact hotline 0243 9743 556 for assistance.
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