The triple test for the diagnosis of Down syndrome includes all of the following, EXCEPT:

Appeared in: DSSSB 13 August 2024

Explanation

Serum prolactin level is not a component of the triple test used for Down syndrome screening.
The triple test specifically measures three markers in maternal serum: alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and unconjugated estriol (uE3).
Prolactin is a hormone primarily responsible for lactation (milk production) and has no established role in screening for fetal genetic abnormalities like Down syndrome.

Option A: Alpha-fetoprotein (AFP) is a key component of the triple test. Its levels are typically decreased in pregnancies affected by Down syndrome.
Option B: Unconjugated estriol (uE3) is a standard marker in the triple test. Its levels are usually low in pregnancies with Down syndrome.
Option C: Human chorionic gonadotropin (hCG) is a critical marker in the triple test. Its levels are characteristically elevated in pregnancies with Down syndrome.

Clinical Relevance

Nursing practice connection: Use the key finding related to Components of the maternal serum triple test for aneuploidy screening to guide bedside assessment, documentation, and the next nursing action.
Nurses must counsel patients that the triple test is a screening tool, not a diagnostic one. A high-risk result indicates an increased probability and necessitates offering further diagnostic testing, such as amniocentesis.
Understanding the components helps in interpreting results and explaining them to anxious parents. For example, low AFP can indicate Down syndrome risk, while high AFP can suggest neural tube defects.
What if? If the test was a 'quadruple test,' the correct answer would still be prolactin. The fourth marker added in the quad screen is Inhibin-A, which is also typically elevated in Down syndrome.

How to Approach the Question

First, identify the core of the question: it asks for the substance that is not part of the triple test.
Note the keyword 'EXCEPT', which signals that three options are correct components and one is the outlier.
Recall the three specific biomarkers measured in the maternal serum triple test: Alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and unconjugated estriol (uE3).
Systematically compare each option to the known components of the triple test.
Identify 'Serum prolactin level' as the option that is not part of this specific screening panel because its primary function relates to lactation.

Concept Tested & Keywords

Concept Tested: Components of the maternal serum triple test for aneuploidy screening.
Stem keywords: triple test, Down syndrome, diagnosis
Lead-in keywords: EXCEPT
Negative lead-in flag: Question asks for the exception.

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E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 1 (pp 26-370 of 370) p. 329-331

E6 Pathology-Vandana Puri & Kavita Gaur Textbook of Pathology and Genetics p. 537-539

E6 Obstetrics Williams p. 4-15

Practise the full DSSSB 13 August 2024

Attempt every question from this paper in a timed mock, then review the full solution for each one.