Prenatal diagnosis technology for older pregnant women, large PK
Release date: 2016-12-23 The laboratory technique for prenatal diagnosis consists of two parts: screening and diagnosis. Screening is an assessment of the risk of fetal abnormality. Diagnosis usually requires invasive techniques. It is a means of diagnosis of fetal abnormalities. Doctors can make clinical treatment based on the prenatal diagnosis results or suggest fetal treatment for pregnant women, but there are certain risks. There are limitations of the application object, restrictions on the acceptance of pregnant women, and restrictions on medical resources. The advantages and limitations of each technology should be fully considered. First, commonly used prenatal diagnostic techniques 1. Fetal cell karyotype analysis: It is the gold standard for the diagnosis of chromosomal diseases. Within the resolution of the visible band, the number and structural abnormalities of all chromosomes can be found and diagnosed, and the information obtained by analyzing the chromosomes is "holographic". The technology requires cell culture, chromosome preparation, karyotyping and other steps, all relying on the manual operation of experienced doctors and technicians, the degree of automation is low, and the inspection and diagnosis cycle is long. 2. Molecular diagnostic techniques: Rapid prenatal diagnostic techniques including fluorescence in situ hybridization, gene amplification-related techniques (such as fluorescence quantitative PCR-related techniques, multiple-link probe amplification techniques), bacterial artificial chromosome markers-magnetic bead separation techniques, etc.; The resolution, the inspection time is shortened, and the detection efficiency is high, but only the target disease set by the kit can be detected, and the abnormality of the genome cannot be analyzed globally. 3. Chromosomal microarray analysis (CMA) technology: Also known as "molecular karyotyping", it can scan at the genome-wide level and detect chromosome copy number variants (CNV), especially for detecting abnormalities such as micro-deletions and duplications. Most of the single parent diploid (UPD) can also be detected, and a certain level of chimera can be detected. The detected pathogenic chromosomal variation is about 10% higher than the traditional G-banding karyotype analysis. Difficulties in clinical application are: insufficient prenatal counseling ability before and after CMA testing, insufficient interpretation ability for clinical significance of test results, and lack of standardized verification of CNV test results. Second, domestic and foreign prenatal screening strategies In the elderly pregnant women, the current prenatal diagnosis strategy in China is to not screen, and the elderly pregnancy is the only indication for the implementation of prenatal diagnosis. The ages defined for the proposed prenatal diagnosis are not the same in the prenatal screening programmes used by countries. European countries such as Canada and the United Kingdom have raised the minimum age of direct amniocentesis in singleton pregnancies to 40 years. In 2007, the American College of Obstetricians and Gynecologists (ACOG) proposed prenatal screening regardless of the age of the pregnant woman. 1. Mother serum prenatal screening: The mother's peripheral blood is collected in early pregnancy and middle pregnancy, and biochemical markers (alpha-fetoprotein, chorionic gonadotropin, pregnancy-specific glycoprotein A, etc.) are measured, and the fetal suffering is calculated in combination with the age, gestational age, and body weight of the pregnant woman. Body, 18–three body risk. The detection rate of prenatal screening for target diseases is only 60%~70%, and there is a high false negative; the screening accuracy is not high, and about 30% of high-risk abnormalities have nothing to do with the target disease. In screening high-risk cases, karyotype analysis of amniotic fluid exfoliated cells can reveal chromosomal abnormalities other than the target disease. Therefore, prenatal screening with Down's syndrome as the main target disease can actually find many different chromosomes. disease. Older pregnant women can stratify fetal abnormalities through prenatal screening, which can greatly reduce unnecessary invasive prenatal diagnosis. 2. Maternal peripheral blood free fetal DNA screening: Noninvasive prenatal testing (NIPT), a high-throughput sequencing, gene chip and other technologies for detecting cfDNA screening for fetal chromosomal abnormalities, is a rapidly developing prenatal screening technique in recent years [14]. Compared with maternal serological screening, the target disease of NIPT screening is accurate, the detection rate of fetal 21-trisomy is over 99%, and the detection rate of 18-trisomy is over 90%-95%, but no target disease can be found. The anomaly is the advantage and the limitation. How does NIPT integrate or change the existing prenatal diagnosis system? It is also a current concern for older pregnant women to use NIPT instead of invasive prenatal diagnosis. Source: Chinese Journal of Laboratory Medicine Frozen Squid Products,Frozen Squid,Frozen Calamari Rings,Frozen Squid Woolworths Zhoushan Fudan Tourism CO., LTD , https://www.fudanfood.com