**Question:** Triple test includes:

A. Serum AFP (alpha-fetoprotein)
B. Serum β-hCG (beta-human chorionic gonadotropin)
C. Serum alpha-fetoprotein and β-hCG combined
D. Serum alpha-fetoprotein and beta-human chorionic gonadotropin combined

**Correct Answer:** D. Serum alpha-fetoprotein and beta-human chorionic gonadotropin combined

**Core Concept:** The triple test is a screening test used in obstetrics to evaluate the risk of Down syndrome in pregnant women. It consists of three components:

1. **Serum alpha-fetoprotein (AFP):** AFP is a protein produced by the developing fetus and placenta. In the presence of increased AFP levels in the maternal serum, it may indicate a high risk of certain congenital anomalies, including neural tube defects and Down syndrome. However, elevated AFP levels can also be seen in other conditions unrelated to fetal anomalies, such as liver disease and malrotation of the intestines.

2. **Serum beta-human chorionic gonadotropin (β-hCG):** β-hCG is a hormone produced by the placenta after fertilization of the egg. In the context of the triple test, elevated levels of β-hCG may indicate a higher risk of Down syndrome. However, like AFP, elevated β-hCG levels can also be found in conditions unrelated to fetal anomalies, such as thyroid disorders and certain cancers.

3. **Combined α-fetoprotein and β-hCG:** The combined measurement of AFP and β-hCG provides a more accurate estimation of the risk of Down syndrome compared to individual AFP or β-hCG measurements alone. The interaction between these two markers helps to discriminate between high-risk and low-risk pregnancies.

**Why the Correct Answer is D:**

The triple test combines the measurement of AFP and β-hCG, which allows for a more comprehensive evaluation of the risk of Down syndrome. This combination helps to differentiate between high-risk and low-risk pregnancies, as the risk increases when both AFP and β-hCG levels are elevated. This is because Down syndrome is associated with elevated levels of both AFP and β-hCG.

**Why Each Wrong Answer is Incorrect:**

A. Serum AFP (Option A) and β-hCG (Option B) individually are not sufficient to accurately assess the risk of Down syndrome. They may be elevated in various non-fetus-related conditions such as liver disease, thyroid disorders, and cancers, which can lead to incorrect risk assessments.

B. Combining AFP and β-hCG (Option C) is not the correct answer because the triple test requires the assessment of both markers together to differentiate between high-risk and low-risk pregnancies for Down syndrome.

**Why Correct Answer D is Correct:**

Combining AFP and β-hCG (Option D) allows for a more accurate assessment of the risk of Down syndrome. This combination provides a more comprehensive evaluation of the risk as the risk increases