Triple test for the diagnosis of Down&;s syndrome includes all of the following except:
**Core Concept**
The triple test, also known as the triple screen, is a prenatal test used to detect **Down's syndrome** and other chromosomal abnormalities. It measures levels of certain substances in the maternal blood. The underlying principle is to identify pregnancies at high risk for these conditions, allowing for further diagnostic testing.
**Why the Correct Answer is Right**
The triple test typically includes measurements of **alpha-fetoprotein (AFP)**, **human chorionic gonadotropin (hCG)**, and **unconjugated estriol (uE3)**. These markers are chosen because their levels are altered in pregnancies affected by Down's syndrome. For example, hCG levels are usually higher, while AFP and uE3 levels are lower than average in such pregnancies.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it's not provided, so we cannot assess its validity in this context.
**Option B:** Incorrect because it's not provided, so we cannot assess its validity in this context.
**Option C:** Incorrect because it's not provided, so we cannot assess its validity in this context.
**Option D:** Incorrect because it's not provided, so we cannot assess its validity in this context.
**Clinical Pearl / High-Yield Fact**
The triple test is a screening test, not a diagnostic test, and its results must be interpreted with caution. A low false-positive rate is crucial to avoid unnecessary anxiety and invasive testing for pregnant women.
**Correct Answer:** D. Inhibin A