Tens of thousands of cases reveal high sensitivity and specificity of noninvasive prenatal genetic testing technology

A non-invasive prenatal gene detection technology (NIFTY) based on massive parallel sequencing (MPS) for fetal chromosomal aneuploidy was evaluated on November 9, 2012 in "Clinical Diagnosis" ) Magazine publication. The scale of this clinical study is as high as 11,105 cases, which lasted for two years. The research was conducted by Shenzhen Huada Gene Research Institute, Shenzhen Huada Clinical Laboratory Center, Capital Medical University, Chinese People's Liberation Army General Hospital, and more than 20 other domestic Home hospital cooperation is completed. Clinical results show that NIFTY has high specificity and sensitivity in the detection of trisomy 21 and trisomy 18. In addition, the researchers also proposed the idea of ​​integrating the NIFTY detection technology based on MPS and establishing a new screening diagnosis model in China.

Abnormal fetal chromosome number is an incidental disease, so far there is no effective treatment, only to a certain degree of prevention through prenatal screening, diagnosis and other means. However, at present, traditional antenatal diagnosis mostly uses invasive sampling methods such as amniocentesis, which may lead to infection and have a certain probability of abortion and other risks. Studies have found that fetal free DNA fragments exist in the peripheral blood of pregnant women. According to this theory, by taking 5 mL of venous blood of pregnant women, the free DNA derived from plasma is extracted therefrom, and MPS technology is used in conjunction with bioinformatics analysis to detect the fetus Risk of chromosomal aneuploidy diseases (such as 21-trisomy also known as Down syndrome, 18-trisomy syndrome, 13-trisomy syndrome). This NIFTY detection technology based on MPS has become a new safety detection method.

In the same type of clinical study, the number of participants varied from 387 to 4664. In this large-scale clinical study, the coverage includes 49 medical centers in 15 provinces and 4 municipalities in China. These medical centers are approved by the Ministry of Health and can be used for prenatal testing and diagnosis. The 11105 participants recruited in this clinical evaluation are at different levels of clinical risk, and all meet the following conditions: pregnant women over 18 years of age, singletons, and within 9-28 weeks of gestation.

After testing tens of thousands of participants for fetal trisomy 21 and trisomy 18 syndrome, a total of 190 patients with abnormal chromosome numbers were detected, including 143 patients with trisomy 21 and 47 trisomy 18 Sign patients. Through karyotype analysis of the positive results and follow-up of the fetus after birth, the researchers found that one of the detected cases of trisomy 21 and trisomy 18 had a false positive; No false negatives were found during follow-up. Therefore, this clinical result shows that the sensitivity of NIFTY technology reaches 100% and the accuracy reaches 99.96%. In addition, there are only 190 (1.17%) patients with abnormal chromosome numbers among the more than 10,000 participants this time, which shows that for 98% of the population, invasive diagnosis can be avoided.

In theory, MPS-based NIFTY detection technology can detect all types of fetal chromosomal aneuploidy abnormalities and microdeletions / microduplications. However, other chromosome abnormalities are relatively rare after 12 weeks of gestation, so clinical trisomy 18 and trisomy 21 are mainly tested. In addition, there are still difficulties in detecting chimeras or chromosomal structural abnormalities. In the two cases of false positives that occurred in this study, the researchers speculated that it might be due to abnormalities in the chromosomal structure of the fetus with micro-repeats and chimeras. Regarding the detection of these special cases, further research is needed.

An ethical problem brought about by MPS-based NIFTY detection technology is that this new method can detect sex chromosomes, which contains fetal gender information. However, according to the current situation in China, it is prohibited for non-medical purposes to disclose gender information before the birth of the fetus. Therefore, for the condition of fetal sex chromosome abnormalities, it is necessary to establish a comprehensive and comprehensive informed consent procedure, so that pregnant women can make the best decision about whether these additional information is needed.

There is no doubt that MPS-based NIFTY detection technology is more efficient in the detection of trisomy 21 and trisomy 18. Although the large-scale promotion of the technology is still limited by its price and reporting time, this situation will soon improve. With the continuous development of high-throughput sequencing, in the near future, this detection technology may be cheaper than traditional invasive methods, and the reporting period will be shortened to 3 days or even shorter. In addition, the increased depth of sequencing will also enable the technology to detect chromosomal structural abnormalities and even single-gene diseases. This new technology will fundamentally change traditional prenatal testing and diagnosis. Of course, in the process of clinical application, it is necessary to establish a comprehensive specification and process, and in this process, pregnant women have sufficient rights to know and choose.

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