Question

The quadruple test doesn't include which of the following?

• A. AFP
• B. Beta hCG
• C. Inhibin
• D. Unconjugated estradiol

Hint:

Prenatal Screening Analytes Breakdown:
- Triple Screen: MSAFP + $\beta$-hCG + unconjugated Estriol (uE3).
- Quadruple Screen: Triple screen analytes + Dimeric Inhibin A.
- Pay attention to Estriol ($E_3$) vs. Estradiol ($E_2$): Quad screen uses ESTRIOL ($E_3$), NOT Estradiol ($E_2$)!

Answer 1

The Correct Option is D

Concept:
The Second-Trimester Quadruple Screen (Quad Screen) is a validated maternal serum biochemical screening test performed between 15 and 22 weeks of gestation (optimally at 16--18 weeks) to evaluate the risk of fetal aneuploidies (Down syndrome, Edwards syndrome) and open neural tube defects (NTDs).
Explanation:
• The Quadruple test evaluates four specific maternal serum analytes:
1. Maternal Serum Alpha-Fetoprotein (MSAFP)
2. Total or Free Beta-Human Chorionic Gonadotropin ($\beta$-hCG)
3. Unconjugated Estriol (uE3)
4. Dimeric Inhibin A (DIA)

• Notice that the quadruple screen specifically measures unconjugated estriol ($E_3$), an estrogen produced exclusively by the coordinated functional interaction of the fetal adrenal glands, fetal liver, and placenta.

• Unconjugated estradiol ($E_2$) is the primary ovary-derived estrogen in non-pregnant females and is NOT an analyte included in the prenatal quadruple screening panel.

• In Down syndrome (Trisomy 21), the classic Quad screen pattern is:
- $\uparrow$ hCG
- $\uparrow$ Inhibin A
- $\downarrow$ MSAFP
- $\downarrow$ uE3 (Remember the mnemonic: HI is High).

• In Edwards syndrome (Trisomy 18), all maternal serum markers ($\text{MSAFP}$, $\text{hCG}$, and $\text{uE3}$) are characteristically decreased ($\downarrow$).
Final Answer:
The quadruple screening panel includes unconjugated estriol ($E_3$) and dimeric Inhibin A; it does not include unconjugated estradiol ($E_2$).