Triple Screen or Quad Screen : labtest

Why Get Tested?
To assess the risk of carrying a fetus with abnormalities, such as Down syndrome, Edwards syndrome (trisomy 18), and open neural tube defects during the second trimester of pregnancy
When to Get Tested?
Women in the 15th to 21st week of pregnancy
Sample Required?
A blood sample drawn from a vein in the arm

How is it used?

The triple or quad screen is used as a screening test in the second trimester of pregnancy. It is ordered to help evaluate the risk that a fetus has certain abnormalities, including Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and neural tube defects such as spina bifida or a condition called anencephaly.
These tests have been established as a triple or quad screen because their power lies in their use together. A mathematical calculation involving the levels of these 3 or 4 substances (AFP, hCG, unconjugated estriol, and, sometimes, inhibin A) and considerations of maternal age, family history, weight, race, and diabetic status are used to determine a numeric risk for Down syndrome and for a few other chromosomal abnormalities such as Edwards syndrome (trisomy 18) in the fetus. This risk is compared with an established cut-off. If the risk is higher than the cut-off value, then it is considered a positive screening test or increased risk exists for carrying a fetus with one of the discussed abnormalities.

An AFP test may be performed by itself and not as part of a triple or quad screen, especially when First Trimester Screening has already been used to assess the risk for chromosomal abnormalities. The AFP is used to help determine the risk of neural tube defects.

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