Diagnostic tests for down syndrome are typically offered to pregnant women who have a higher chance of having a baby with the condition based on their age or other risk factors. This article summarises the types of tests to diagnose down syndrome and the reasons of performing these tests.
What are the diagnostic tests done for down syndrome?
There are two basic types of tests available to diagnose down syndrome in the foetus during pregnancy, screening tests and diagnostic tests. Other than these two tests, you can also get a genetic testing (chromosome analysis).
The screening tests include a combination of a blood test and an ultrasound scan to determine the risk of down syndrome. The blood tests are called Triple Screen or Quad screen, and they measure a number of substances in the mother’s blood like MS-AFP, human chorionic gonadotropin, estriol and inhibin A. The ultrasound scan displays a picture of the foetus. Extra fluid behind the neck of the foetus can indicate a genetic condition.
There are 3 types of diagnostic tests, i.e., Chorionic Villus Sampling (CVS), which examines material from the placenta; amniocentesis, which examines the amniotic fluid (the fluid from the sac surrounding the baby); and Percutaneous Umbilical Blood Sampling (PUBS), which examines the blood from the umbilical cord. These tests find out if there are any changes in the chromosomes indicating down syndrome.
Why are diagnostic tests performed for down syndrome?
Diagnostic tests for down syndrome are performed to confirm whether a developing fetus has the condition. According to the CDC (Center for Disease Control and Prevention), diagnostic tests are generally conducted after the screening tests have come back positive. These are typically offered to pregnant women who have a higher risk of having a baby with down syndrome based on factors such as maternal age, abnormal ultrasound findings, or a family history of the condition. According to the National Human Genome Research Institute, the diagnosis of down syndrome can be done in infancy on the basis of characteristic clinical findings. Whenever down syndrome is suspected, a genetic test called chromosome analysis is performed on a blood or skin sample to look for the inconsistency in the chromosomes.
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