Triple Marker Test: Detailed Information
The triple marker test is a key part of second-trimester screening to evaluate the health of a fetus and the risk of congenital abnormalities. Below are more comprehensive details:
Components of the Triple Marker Test :
1. Alpha-fetoprotein (AFP):
• Produced by: The fetal liver.
• Normal levels: Vary with gestational age.
• High levels:
• Neural tube defects (e.g., spina bifida, anencephaly).
• Abdominal wall defects (e.g., gastroschisis, omphalocele).
• Multiple pregnancies (twins, triplets).
• Incorrect gestational dating.
• Low levels:
• Chromosomal abnormalities (e.g., Down syndrome, Edwards syndrome).
2. Human Chorionic Gonadotropin (hCG):
• Produced by: The placenta.
• High levels: Suggestive of Down syndrome or molar pregnancy.
• Low levels: Indicative of Edwards syndrome or potential miscarriage.
3. Estriol (uE3):
• Produced by: The fetal adrenal glands and placenta.
• Low levels:
• Chromosomal abnormalities like Down syndrome and Edwards syndrome.
• Poor fetal development or placental dysfunction.
Test Procedure
• Timing: Between 15–20 weeks of pregnancy, with optimal results around 16–18 weeks.
• Sample type: A small blood sample is drawn from the mother’s arm.
• Preparation: No special preparation is required, but providing accurate gestational age is crucial for reliable results.
Dear patients, for triple marker testing, provide the following information:
1. Latest Sonography report 2 xerox copy
2. Height
3. Weight
4. LMP
5. Date of Birth
6. Previous pregnancy history, if any.
Test Interpretation
Results are presented as:
1. MoM (Multiple of the Median): A ratio comparing the patient’s results to the median value for their gestational age.
2. Risk Assessment: Based on a combination of biochemical markers and maternal factors (age, weight, ethnicity, gestational age).
Risk Profiles:
• Increased risk of Down syndrome:
• Low AFP, high hCG, and low estriol.
• Increased risk of Edwards syndrome:
• Low AFP, low hCG, and low estriol.
• Increased risk of neural tube defects:
• High AFP with normal hCG and estriol.
Advantages of the Triple Marker Test
1. Non-invasive: Only requires a maternal blood sample.
2. Screening for multiple conditions: Neural tube defects and chromosomal abnormalities.
3. Guides further testing: Identifies pregnancies that may benefit from amniocentesis or high-resolution ultrasound.
Limitations
1. Screening, not diagnostic: Abnormal results do not confirm a condition but indicate a need for further evaluation.
2. False positives/negatives: Results can be influenced by:
• Incorrect gestational dating.
• Maternal factors (e.g., obesity, diabetes).
3. Not a universal test: Offered mainly to women at higher risk (e.g., advanced maternal age, family history).
Follow-up Tests
1. Amniocentesis: Analysis of amniotic fluid to confirm chromosomal abnormalities.
2. Ultrasound: To detect structural anomalies like neural tube defects.
3. NIPT (Non-Invasive Prenatal Testing): A more sensitive blood test analyzing fetal DNA.
Clinical Relevance
The test is especially recommended for:
1. Women over the age of 35.
2. Family history of genetic disorders.
3. Previous pregnancies with chromosomal abnormalities.
4. Abnormal findings on earlier screening or ultrasounds.
References:
1. American College of Obstetricians and Gynecologists (ACOG).
Practice Bulletin No. 163: Screening for Fetal Aneuploidy.
American College of Obstetricians and Gynecologists, 2016.
• This practice bulletin discusses screening tests for aneuploidy, including the triple marker test, and provides guidelines on its use.
2. Mayo Clinic.
Triple screen test: MedlinePlus Medical Encyclopedia.
Mayo Clinic, 2023.
• A comprehensive source that covers the procedure, interpretation, and implications of the triple screen test.
3. Williams Obstetrics, 26th edition.
Cunningham, F.G., et al., McGraw-Hill, 2022.
• This textbook includes detailed discussions on prenatal screening, including the triple marker test and its components.
4. National Center for Biotechnology Information (NCBI).
Maternal Serum Triple Marker Screening Test.
PubMed Central (PMC), 2023.
• A peer-reviewed article available through NCBI that provides an overview of the triple marker test, including its clinical uses, limitations, and interpretation.
5. National Institute for Health and Care Excellence (NICE).
Antenatal care: Routine care for the healthy pregnant woman.
NICE Guidelines, 2019.
• Offers guidance on prenatal care, including screening for chromosomal abnormalities and neural tube defects, with references to the triple marker test.
6. Genetics Home Reference.
Screening Tests During Pregnancy: Triple Screen.
U.S. National Library of Medicine, 2020.
• An informative resource detailing the biochemical markers and the significance of the triple marker test in detecting genetic conditions.
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