Normal range for唐screening of trisomy 18
Sep 13, 2022
Source: Cainiu Health
Dr. Lv Aiming
Introduction
The normal value for trisomy 18 syndrome is generally below 1:1,000; borderline high risk is typically defined as 1:271 to 1:1,000; and high risk is considered above 1:271. Therefore, a risk value of 1:350 for trisomy 18 syndrome falls within the borderline range. Different hospitals may use varying testing methods; common screening for trisomy syndromes such as Down syndrome often involves measurements of troponin and human chorionic gonadotropin (hCG).
Trisomy 18 syndrome, also known as Edwards syndrome, refers to the presence of three copies of chromosome 18 in a human cell. So what is the normal reference range for Trisomy 18 screening in prenatal testing?
Normal Reference Range for Trisomy 18 Screening
The normal risk value for Trisomy 18 is generally below 1:900. Intermediate risk ranges from 1:271 to 1:900, while high risk is indicated by values above 1:271. Therefore, the borderline risk value for Trisomy 18 syndrome is typically considered to be 1:350. The normal reference values may vary slightly between hospitals, but usually, the pregnancy-associated plasma protein-A (PAPP-A) level should be greater than 2.6 MoM (multiples of median). Generally, the higher the level of human chorionic gonadotropin (hCG), the greater the risk of fetal chromosomal abnormalities such as Down syndrome. Factors including PAPP-A levels, hCG levels, maternal age, weight, and gestational age are input into a computer algorithm to calculate whether the risk is high, intermediate, or low.
If the initial screening results are abnormal, further diagnostic tests such as amniocentesis at the hospital or blood-based genetic testing can be performed. If the test results are normal and there is no cause for concern, it is recommended to undergo a detailed four-dimensional color ultrasound examination at 24–26 weeks of gestation, followed by a comprehensive anomaly scan.
This screening requires drawing venous blood from the pregnant woman and combining it with factors such as maternal weight, age, gestational week, and fetal size for comprehensive analysis. It is a crucial examination during pregnancy. Expectant mothers must not miss the appropriate testing window. We hope this answer has been helpful to you. Wishing you good health and happiness!
