Medical analysis

Quad Marker Study

By: Dr. Dipak Ladda M.D.

Introduction – quadruple marker test

The Quadruple Marker Test, also known as the Quad screen test, is a prenatal screening test used to assess the risk of certain genetic disorders and neural tube defects in a developing foetus.

This non-invasive test measures the levels of four substances in the mother’s blood: Alpha-Fetoprotein, Human Chorionic Gonadotropin, Unconjugated Estriol & Inhibin A.

This test is advised to all pregnant women, especially if they report a family history of genetic problems.

It carries 70% sensitivity and 5% false positivity rates.

Assay Substances Produced By

During interpretation of the results, age of the mother, weight & ethnicity must be considered. These markers help in assessing the risk of the fetus having chromosomal abnormalities eg. Down’s Syndrome, Neutral Tube Defect.

How the test is done?

It is performed between 15 – 20 weeks of pregnancy. Required items to interpret the report of Quad Screen include a sonography report of anomaly scan with age of gestation, height, Weight & Ethnicity, Date of Birth, and LMP.

How this test to be moved?

01: Get done this test between 15th and 20th weeks of pregnancy. It is advisable especially for those pregnant women; who are having family history of genetic issues, diabetic and age 35 years or above, to get this done.

02: Discuss in details with patient i.e. Purpose of the test, benefits and potential risk of results.

03: Ultrasound examination reports are must.

04: This test does not provide definite diagnosis but shows a risk in proportion for chromosomal abnormalities.

05: Your doctor may recommend further tests like amniocentesis to confirm suspected abnormalities.

06: Genetic counseling for implications of findings.

Role of Ultrasound in Quadruple Marker

Quad Screen points towards Down’s Syndrome or neural tube defects. However, for detecting physical anomalies like cardiac structural defects, brain anomalies or defects in various other organs, an anomaly scan always remains a choice; which also helps to correlate results.

Ultrasound helps to:

• To confirm gestational age: Accurate dating possible.
• To detect any other gross structural abnormality.
• Assesses in calculating combined risk for chromosomal abnormalities.
• Helps in comprehensive genetic counseling and explaining implications of the screening results.

Sample Collection & Transportation

Collect 3.0 ml blood in plain tube (Red capped). Separate serum as early as possible and send to lab. Include required information such as Patient’s date of birth, weight and LMP, and Ultrasound anomaly scan report along with fetus age.

Assay Methods & Reference Range

Refer ppts of hCG, AFP, uE3 (Unconjugated estriol) & Inhibin A.

Responsibility of Doctor to Provide Following Information

The doctor must provide: Weight (kgs) & Height (cms) of patient, history of previous pregnancy to help assess the risk, information on things which can cause changes in hormonal levels (eg. Diabetes, HCG injections or any other medications), and for IVF conception (risk assessment is related with Date of Birth of Donor).

Accurate Ultrasound report is must. Total sensitivity and accuracy of the test results vary with ultrasound report.

Purpose of Quadruple Marker Test

It is calculated by combining the biochemical results obtained (values of hCG, AFP, Ue3 & Inhibin A) with the patient’s information along with sonography anomaly scan report.

The Quad Screen primarily screens for major genetic issues in the fetus, such as:

Down’s syndrome: Caused by an extra copy of chromosome 21.

Neural tube defects: When the spinal cord or brain fails to develop properly.

Edwards syndrome (Trisomy 18): Extra chromosome 18.

Trisomy 13 (Patau syndrome): Extra chromosome 13 (Not that much reliable).

The test calculates, based on maternal blood markers, whether the fetus falls into a high or low-risk zone for these common chromosomal issues.

How Quadruple Marker Test Helps?

Software calculates the risk probabilities based on the hormone levels. Results indicate high or low chances of genetic issues. If high risk, further invasive testing is suggested to confirm diagnosis.

Uses of Quad Test Screen

May become vigilant for additional prenatal diagnostic testing. Warning signal passes to parents and get mentally prepared for high-risk pregnancy; including forthcoming genetic abnormalities. Doctor and parents both become ready for intervention during pregnancy.

MoM (Multiple of Median)

Multiple of Median: When multiple parameters show results deviating from their median value.

MoM: Patient’s Results / Median Value for Gestational Age.

Median Value for Gestational Age: It is calculated by taking mean from the reference population for the same gestational age.

Markers Reference Range (Multiple of Median)

Levels of Various Biochemical Assay Interpretation

Comments & Limitations

Parents must be informed about test platform, software used and disclaimers associated with screening test. Essential to know that this is a simple screening test and it does not offer any concrete diagnosis. It only suggests risk associated with pregnancy. It facilitates doctor to decide for additional tests for further evaluation or confirmation. Negative test result does not guarantee absolute healthy baby.

References:

• American College of Obstetricians and Gynecologists. Practice Bulletin No. 226: Screening for Fetal Chromosomal Abnormalities. Obstet Gynecol. 2020;136(4):e48-e69.
• Wald NJ, Cuckle HS, Densem JW, et al. Maternal serum screening for Down syndrome in early pregnancy. BMJ. 1988;297(6653):883-887.
• Haddow JE, Palomaki GE, Knight GJ, et al. Screening of maternal serum for fetal Down’s syndrome in the first trimester. N Engl J Med. 1998;338(14):955-961.
• Spencer K, Spencer CE, Power M, et al. Screening for chromosomal abnormalities in the first trimester using ultrasound and maternal serum biochemistry in a one-stop clinic: a review of three years prospective experience. BJOG. 2003;110(3):281-286.
• Malone FD, Canick JA, Ball RH, et al. First-trimester or second-trimester screening, or both, for Down’s syndrome. N Engl J Med. 2005;353(19):2001-2011.
• Wald NJ, Rodeck C, Hackshaw AK, et al. SURUSS in perspective. Semin Perinatol. 2005;29(4):225-235.
• Palomaki GE, Knight GJ, Kloza EM, et al. A comprehensive approach to first-trimester screening for trisomy 21. Am J Obstet Gynecol. 2006;194(4):1122-1130.
• Breathnach FM, Malone FD. Screening for aneuploidy in first and second trimesters: is there an optimal approach? Curr Opin Obstet Gynecol. 2007;19(2):176-182.
• Kagan KO, Wright D, Spencer K, et al. First-trimester screening for trisomy 21 by free beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A: impact of maternal and pregnancy characteristics. Ultrasound Obstet Gynecol. 2008;31(5):493-502.
• Wright D, Spencer K, Kagan KO, et al. First-trimester sonographic markers for trisomy 21: a study of 12 188 fetuses. Ultrasound Obstet Gynecol. 2008;32(7):874-880.
• Nicolaides KH. Screening for fetal aneuploidies at 11 to 13 weeks. Prenat Diagn. 2011;31(1):7-15.
• The Fetal Medicine Foundation. Screening for chromosomal abnormalities in the first trimester. [Online Resource].
• Wilson RD. Amended Canadian Guideline for prenatal diagnosis (2005) change to 2005—techniques for prenatal diagnosis. SOGC Clinical Practice Guidelines, No. 168. J Obstet Gynaecol Can. 2005;27:1048–1054.
• Jindal A, et al. Reference Centile Charts of PAPP-A and Free β-hCG in Indian Pregnant Women. Int J Sci Res. 2021.
• Journal of Nursing Reports in Clinical Practice. The first-trimester screening to detect chromosomal abnormalities in pregnant women: A retrospective study. 2023.

FAQ:

• What is a quad marker test? It is a prenatal screening test measuring four blood substances to assess fetal genetic and developmental risks.
• When is the test performed? The test is conducted between the 15th and 20th weeks of pregnancy.
• What four markers are measured? It measures Alpha-Fetoprotein, Human Chorionic Gonadotropin, Unconjugated Estriol, and Inhibin A levels.
• Is it a diagnostic test? No, it is a screening test showing risk proportions, not a final diagnosis of abnormalities.
• Who should undergo this test? It is advised for pregnant women, especially those with family genetic history, diabetes, or aged 35-plus.
• What conditions does it screen? It screens for Down’s syndrome, neural tube defects, Edwards syndrome, and Trisomy 13.
• Why is ultrasound report required? It confirms accurate gestational age and detects structural anomalies, which are vital for correct risk calculations.
• What does MoM represent? MoM (Multiple of Median) indicates how much a patient’s results deviate from the reference population median.
• What information must doctors provide? Doctors must provide patient height, weight, LMP, age, and an accurate ultrasound anomaly scan report.
• What if the result’s high-risk? If high-risk, further invasive testing like amniocentesis is recommended to confirm potential genetic abnormalities.

 For Non-Medicos:

Overview

The Quadruple Marker Study, also known as the Quad Screen, is a prenatal screening test used to estimate the risk of major chromosomal abnormalities and neural tube defects in a developing fetus. According to the document, this non-invasive blood test measures four essential biochemical markers in the mother’s serum: Alpha-Fetoprotein (AFP), Human Chorionic Gonadotropin (hCG), Unconjugated Estriol (uE3), and Inhibin A (page 2). Each marker originates from a specific fetal or placental source – AFP from the fetal liver, hCG from the placenta, uE3 from both fetal liver and placenta, and Inhibin A from placental trophoblasts (page 3).

The test is performed between 15–20 weeks of pregnancy (page 4) and provides a probability-based assessment, not a definitive diagnosis. It helps identify risks for Down’s syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), Patau syndrome (Trisomy 13), and Neural Tube Defects (page 10). It carries 70% sensitivity with a 5% false-positive rate (page 2), making it an important first-line screening tool in routine antenatal care.

Symptoms

Since the Quad Marker test is a screening procedure, the “symptoms” reflect maternal or fetal indicators that prompt clinicians to recommend the test.

1. High-risk pregnancy indicators

The document suggests screening is especially advised for women who:

1. 1. Have a family history of genetic disorders (page 2)

1. 1. Are 35 years or older (page 5)

1. 1. Have diabetes or are on fertility treatments such as HCG injections (page 9)

1. 1. Conceived through IVF, where donor age must be accounted for (page 9)

2. Abnormal ultrasound findings

The anomaly scan is necessary for interpreting the report (page 4), and clinicians may recommend the Quad Marker when ultrasound indicates:

1. 1. Abnormal fetal growth

1. 1. Structural concerns, such as cardiac or brain anomalies

1. 1. Suspected gestational age mismatch

3. Previous pregnancy complications

A history of miscarriage or chromosomal abnormality is listed as a factor influencing risk assessment (page 9).

Thus, symptoms prompting testing are related to risk elevation, not maternal illness.

Causes

The underlying “causes” relate to the biological and analytical factors measured through the Quad Marker study.

1. Variations in fetal and placental biochemistry

Abnormal levels of AFP, hCG, uE3, and Inhibin A drive the interpretation. The document outlines these patterns (page 15):

1. 1. High AFP → Neural tube defects (e.g., spina bifida, anencephaly)

1. 1. Low AFP + low uE3 + high hCG → Down’s syndrome

1. 1. Low AFP + low uE3 + low hCG → Edwards syndrome

1. 1. High hCG → Down’s, twins, or triploidy

1. 1. High Inhibin A → Down’s syndrome

2. Gestational age discrepancies

Accurate dating—verified via ultrasound—is critical because incorrect gestational age causes misinterpretation (page 6).

3. Maternal physiological factors

Maternal weight, ethnicity, medical history, and medications affect hormone levels (pages 3 & 9), influencing results.

4. Biochemical assay interpretation

Markers are evaluated using Multiples of Median (MoM) (page 13–14), comparing patient values against expected medians for the same gestational age.

Risk Factors

Risk factors fall into two categories: maternal/fetal risks and testing/interpretation-related risks.

Maternal & Fetal Risk Factors

1. 1. Advanced maternal age (page 5)

1. 1. Diabetes or hormonal treatment (e.g., HCG injections) (page 9)

1. 1. Genetic disorder history (page 2)

1. 1. IVF conception, requiring donor age consideration (page 9)

1. 1. Previous abnormal pregnancy outcomes

These factors may alter marker levels or increase the likelihood of chromosomal abnormalities.

Technical & Interpretation Risk Factors

The document lists essential considerations:

1. 1. Results depend on exact gestational age (page 6).

1. 1. Inaccurate ultrasound reduces the sensitivity of the test (page 9).

1. 1. Incomplete patient information—missing weight, LMP, ethnicity—can distort risk calculations (pages 7 & 9).

1. 1. The test offers risk probability, not a definitive diagnosis (pages 5 & 16).

1. 1. False-positive and false-negative outcomes are possible due to biological variation (page 16).

Prevention

Here, “prevention” refers to preventing misinterpretation, unnecessary anxiety, and ensuring reliable screening outcomes.

1. Accurate sample collection & documentation

Collect 3 ml of blood in a plain tube, separate serum quickly, and include essential details such as DOB, weight, LMP, and ultrasound report (page 7).

2. Mandatory anomaly scan correlation

Ultrasound is crucial for confirming gestational age and structural integrity (page 6).

3. Patient counseling

Discuss test purpose, limitations, and implications thoroughly (page 5). Patients must know this is a screening test, not a diagnostic tool (page 16).

4. Follow-up diagnostic tests

If high risk, clinicians may recommend amniocentesis or other invasive tests to confirm abnormalities (pages 5 & 11).

5. Genetic counseling

Essential for understanding the impact of results and preparing parents for potential high-risk pregnancy outcomes (page 6).

6. Clinical correlation

Negative results do not guarantee a completely healthy baby (page 16). Preventive accuracy comes from correlating biochemical markers, maternal factors, and ultrasound findings.