Quad Screen Test: Purpose, Procedure and Accuracy

Quad Screen Test: Purpose, Procedure and Accuracy

In the realm of prenatal care, there are various tests and screenings available to assess the health and development of the fetus. One such test that plays a crucial role in this process is the quad screen. The quad screen, short for quadruple marker screen, is a routine prenatal test that provides valuable information about the health of both the fetus and the mother. In this comprehensive guide, we will delve into the details of the quad screen, its purpose, the procedure involved, and its accuracy, among other important aspects.

Table of Content

  • What is a quad screen?
  • Why is it called a quad screen?
  • What does the quad screen test for?
  • When Should the Quad Screen Be Done?
  • Does everyone get a quad screen?
  • Quad Screen Test Cost
  • How is the quad marker screen done?
  • What does the quad screen check?
  • How the results are determined
  • How accurate is the quad screen test?

What is a Quad Screen?

The quad screen is a non-invasive prenatal test performed during the second trimester of pregnancy, typically between the 15th and 20th week. It is also known as the quadruple marker screen, multiple marker screening, or simply the quad marker test. This test evaluates specific substances in the mother's blood to assess the risk of certain genetic and chromosomal abnormalities in the developing fetus.

Why is it Called a Quad Screen?

The name "quad screen" is derived from the fact that it measures four specific markers or substances in the mother's blood. These markers are:

  • Alpha-fetoprotein (AFP)
  • Human chorionic gonadotropin (hCG)
  • Estriol (uE3)
  • Inhibin A

These four markers are collectively used to assess the risk of certain birth defects and genetic conditions in the fetus, hence the name "quad screen."

What Does the Quad Screen Test For?

The quad screen is primarily used to screen for the following conditions:

  • Neural Tube Defects (NTDs): The quad screen measures the level of alpha-fetoprotein (AFP) in the mother's blood. An elevated AFP level may indicate an increased risk of neural tube defects such as spina bifida and anencephaly.
  • Down Syndrome (Trisomy 21): Abnormal levels of hCG, estriol, and inhibin A can be associated with an increased risk of Down syndrome, a chromosomal abnormality.
  • Trisomy 18 (Edwards Syndrome) and Trisomy 13 (Patau Syndrome): The quad screen can also detect abnormal levels of these markers, which are associated with these rare but serious genetic conditions.

When Should the Quad Screen Be Done?

The quad screen is typically offered to pregnant women between the 15th and 20th week of pregnancy. This timing is crucial because it allows for the detection of certain abnormalities, such as neural tube defects and chromosomal disorders, while still providing ample time for informed decision-making regarding the pregnancy.

It's important to note that the quad screen is not mandatory, and the decision to undergo this test is ultimately up to the expectant mother. Some women may choose not to have the quad screen or may opt for other prenatal tests instead.

Does Everyone Get a Quad Screen?

The quad screen is typically offered to all pregnant women as a part of routine prenatal care. However, not everyone chooses to have the test, and some may have specific reasons for opting out. Additionally, women with certain risk factors, such as advanced maternal age or a family history of genetic conditions, may be more strongly encouraged to undergo the quad screen or other genetic testing options.

Quad Screen Test Cost

The quad screen test is a prenatal screening procedure widely used in India to assess the risk of certain genetic disorders in a developing fetus. The quad screen test cost in India can vary significantly depending on several factors. Generally, the test's price ranges from INR 2,000 to INR 4,000, but it may be higher in some metropolitan cities and renowned medical facilities.

The variability in cost is influenced by factors such as the location of the healthcare facility, the brand of the laboratory, and whether it is performed as part of a comprehensive prenatal screening package. Additionally, some healthcare providers offer subsidized or discounted rates for this test to make it more accessible to expectant parents. It is crucial for individuals to inquire about the specific cost at their chosen healthcare facility and consider the potential benefits of early detection when deciding whether to undergo the Quad Screen Test during pregnancy.

How is the Quad Marker Screen Done?

The quad screen is a straightforward and minimally invasive procedure. Here's a step-by-step overview of how the test is typically conducted:

  • Blood Sample Collection: The healthcare provider or a phlebotomist will draw a blood sample from a vein in your arm. The sample is subsequently delivered to a lab for evaluation.
  • Laboratory Analysis: In the laboratory, the levels of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), estriol (uE3), and inhibin A are measured in your blood.
  • Risk Assessment: The results of the quad screen are used to assess your risk for specific conditions, such as neural tube defects and chromosomal disorders. The results are usually reported as a probability or a risk score.

What Does the Quad Screen Check?

Each of the four markers measured in the quad screen serves a specific purpose in assessing fetal health:

  • Alpha-fetoprotein (AFP): Elevated levels of AFP can suggest the presence of neural tube defects, such as spina bifida or anencephaly. Low AFP levels may be associated with an increased risk of Down syndrome.
  • Human Chorionic Gonadotropin (hCG): Abnormal hCG levels may indicate an increased risk of Down syndrome or other chromosomal abnormalities.
  • Estriol (uE3): Estriol is a hormone produced by both the fetus and the placenta. Low estriol levels can be associated with Down syndrome, while elevated levels may indicate a healthy pregnancy.
  • Inhibin A: Elevated inhibin A levels are often linked to an increased risk of Down syndrome and other chromosomal abnormalities.

How the Results are Determined

Interpreting the results of the quad screen involves considering several factors, including the levels of the four markers, the mother's age, and the gestational age of the fetus. The results are usually reported as either "screen-positive" or "screen-negative."

  • Screen-Positive: A screen-positive result means that the risk for certain conditions, such as Down syndrome or neural tube defects, is higher than the average population risk. However, it's essential to understand that a screen-positive result does not provide a definitive diagnosis. Further diagnostic tests, such as amniocentesis or chorionic villus sampling (CVS), may be recommended to confirm the presence of a condition.
  • Screen-Negative: A screen-negative result indicates that the risk for the assessed conditions is within the expected range for the general population. It is a reassuring result, but it does not guarantee that the fetus is free of all abnormalities.

It's crucial to discuss the results with your healthcare provider to understand their implications fully and decide on any further steps if necessary.

How Accurate is the Quad Screen Test?

The accuracy of the quad screen test varies depending on the specific condition being assessed. Here's a breakdown of the test's accuracy for the most common conditions:

  • Neural Tube Defects (NTDs): The quad screen can detect about 80-85% of neural tube defects when performed between the 15th and 20th week of pregnancy. However, it is not as accurate as more invasive diagnostic tests like amniocentesis or CVS.
  • Down Syndrome (Trisomy 21): The quad screen can identify approximately 80-85% of pregnancies affected by Down syndrome. Again, it is not a definitive diagnostic test, and further testing may be required for confirmation.
  • Trisomy 18 (Edwards Syndrome) and Trisomy 13 (Patau Syndrome): The quad screen is less effective at detecting these conditions, with a lower accuracy rate than for Down syndrome.

It's important to remember that the quad screen is a screening test, not a diagnostic one. A screen-positive result may indicate an increased risk, but a diagnostic test, such as amniocentesis or CVS, is needed to confirm the presence of a condition with certainty.

In summary, the quad screen is a valuable tool in prenatal care, providing expectant parents with information about the health of their developing fetus. By measuring four specific markers in the mother's blood, it can assess the risk of conditions such as neural tube defects and chromosomal abnormalities. However, it's essential to understand that the quad screen is not a definitive diagnostic test, and its results are used to determine the need for further testing.

If you are pregnant or planning to become pregnant, discussing the quad screen with your healthcare provider can help you make informed decisions about your prenatal care. Understanding the purpose, procedure, and accuracy of this test is a crucial step in ensuring the health and well-being of both you and your baby during pregnancy.

Quad Screen FAQ

Q: What is the ideal time during pregnancy to have the quad screen test done?
A:
The quad screen is typically performed between the 15th and 20th week of pregnancy, which is the second trimester.

Q: Is the quad screen mandatory for all pregnant women?
A:
No, the quad screen is not mandatory. It is typically offered as part of routine prenatal care, but the decision to undergo the test is ultimately up to the expectant mother.

Q: Can the quad screen provide a definitive diagnosis of conditions like Down syndrome?
A:
No, the quad screen is a screening test, not a diagnostic one. A screen-positive result indicates an increased risk, but a diagnostic test like amniocentesis or chorionic villus sampling (CVS) is needed for confirmation.

Q: Are there any risks associated with the quad screen test?
A:
The quad screen is a low-risk blood test, and complications are rare. The most common risk is the possibility of receiving a false-positive result, which may lead to unnecessary anxiety and further testing.

Q: Can the quad screen determine the gender of the baby?
A:
No, the quad screen is not used to determine the gender of the baby. It focuses on assessing the risk of specific genetic and chromosomal conditions.

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About Author

Dr. Aayush Mittal

Studied at Govt. Sr. Sec. School, he has established himself into a renowned personality after becoming an experienced dentist and cosmetic implantologist. He received his bachelors in BDS from Dr Vasantrao Pawar Medical College, Nashik. After receiving the bachelors, he became the resident doctor at Sardar Patel Medical College and PBM Hospital, Bikaner Rajasthan, India. After that, he received his fellowship from the USA and specialty, i.e, MDS from Jaipur National University Institute For Medical Sciences & Research Centre, 302017

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