Triple Screening In Pregnancy – Essential Elements, Process And Accuracy
One of the biggest fears for a pregnant woman is the risk of her baby having abnormalities such as Down Syndrome, Edwards Syndrome or nueral tube defects. The fear is understandable, as the anamolies can have a dibilitating effect on the child. With technology advancing at a pace like never before, it is now possible to find out the defects in the baby in the womb itself through the triple screening test.
What Is The Triple Screen Test?
A triple screen test, also called the kettering test or triple screen or the Bart’s test, is a blood screening test that checks alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), (1) and estriol.
- AFP: Fetus produces the AFP protein.
- HCG: The hormone is produced in the placenta.
- Estriol: Both the placenta and the fetus produce estrogen called estriol.
All the three leave their traces in the mother’s bloodstream. The test helps doctors analyze the possibility of birth defects in the baby.
Need For A Triple Screening Test In Pregnancy:
Going for a triple screening test in the second trimester of pregnancy would help you get a clue of possible abnormality in the fetus. The test is highly recommended for women who:
- Have a family history of birth defects.
- Are aged 35 years or more.
- Consumed harmful drugs or medications during pregnancy.
- Are exposed to high radiation levels.
- Are diabetic and using insulin.
- Are affected with viral infection during pregnancy.
When And How Is Triple Test Performed?
The triple screen test is performed between 15th and 20th week. The simple test involves drawing blood samples from you and testing them in a laboratory. The results are usually out within a few days.
What Are Analyzed In The Triple Screen Test In Pregnancy?
Triple screening test in pregnancy analyzes AFP levels, besides abnormal levels of hCG and estriol.
- High AFP (also known as Maternal Serum AFP, or MSAFP) levels indicate spina bifida or anencephaly, a neural tube defect in growing baby.
- Low AFP levels and abnormal hCG and estriol levels indicate Down Syndrome (Trisomy 21) (2), Edwards Syndrome (Trisomy 18) (3) or other chromosomal abnormalities.
- The test also helps in identifying multiple pregnancy as well as the advancement of pregnancy.
While analyzing the results, the risk is calculated after considering the following:
- The Age of the expectant mother.
- If the mother is carrying More than one fetus. Multiple fetuses increase the levels of MSAFP because each fetus secretes its own AFP.
- If she is Diabetic because those dependent on insulin have 20% lower levels of MSAFP than normal women.
- Gestational age of the baby. Incorrect calculation of gestation is a common cause for showing abnormal MSAFP levels.
- Weight of the mother, as the MSAFP level decreases with the increase in the maternal weight.
- Ethinicity is also considered before concluding on the triple screen test results. For example: African-American women have 10-15% higher MSAFP than Caucasian women.
How Accurate Is Triple Test In Pregnancy?
- Triple test is considered to be most accurate when performed between the 16th and 18th week of pregnancy. It has a 70% sensitivity and 5% false-positive rate.
- The accuracy of a screening test is based on the number of times it correctly identified birth defects.
- In 80 out of 100 fetuses, the triple and quad tests rightly found tube defects like spina bifida.
- The tests correctly found anencephaly in 90 out of 100 fetuses.
- In 69 out of 100 fetuses, the triple tests successfully detected down syndrome.
- In 81 out of 100 fetuses, the quad tests successfully found down syndrome. (4)
What Do Results Of Triple Screen Test Indicate?
Screening tests do not diagnose a problem but signal the requirement for further tests. Same is the case with triple screen test, which is not diagnostic. The test only indicates the probability of a mother carrying a baby with a genetic disorder.
The results of the triple screening are usually available in one or two weeks. A positive result means that there is an increased risk of chromosomal and neural tube defects. In such cases, the expectant mother is made to undergo diagnostic tests.
Further Testing To Diagnose Abnormalities:
Additional testing is required when triple screen results show something abnormal. As a conservative method, a second triple screen is usually performed, followed by a high definition ultrasound. The ultrasound test can check the age of the baby, its spinal cord, kidneys, heart, and brain for any defects.
An invasive procedure called amniocentesis (5) may be performed if the abnormal results repeat. It helps in checking the baby’s chromosomes and tracking the problems, if any. Performing further tests could diagnose the issue and help consider an option that is good for both the unborn baby and mother.
Are There Any Risks Associated With Triple Test?
The non-invasive blood test procedure has little risk to both mother and the fetus. There could be some discomfort while drawing blood but no side effects are linked to triple screening test in pregnancy.
Variations Of Screen Tests:
Sometimes, the term ‘multiple-marker screening test’ is used instead of triple screening test. This includes double test and quadruple test.
1. Double Test:
Double marker test is a blood test where free beta hCG and PAPP-A (pregnancy associated plasma protein) markers are checked in the blood.
High level of Free Beta hCG indicates risk of Down Syndrome and low level Trisomy 18 and 21.
Low level of PAPP-A indicates risk of Down Syndrome and Trisomy 18 and 21.
Double marker test is done between 10-13 weeks of pregnancy. A double test is considered obsolete in the UK.
2. Quadruple Test:
It is also called quad test or quad screen or tetra screen. While the triple screen measures the levels of AFP, hCG and estriol in your blood, quad screen additionally tests for a hormone called ‘Inhibin A’, Which is made by placenta. The quad screen is performed between 14 and 22 weeks.
When taken between 15 and 18 weeks of gestational age, the quad screen has 81% sensitivity and 5% false-positive rate for detecting Down syndrome.
Quad Screen Test
The quad screen test is a maternal blood screening test that looks for four specific substances: AFP, hCG, Estriol, and Inhibin-A.
Estriol : estriol is an estrogen produced by both the fetus and the placenta
Inhibin-A : inhibin-A is a protein produced by the placenta and ovaries
The quad screen is a maternal blood screening test which is similar to the Triple Screen Test (also know as AFP Plus and the Multiple Marker Screening). However, the quad screen looks for not only the three specific substances evaluated in those tests (AFP, hCG, and Estriol) but also a fourth substance known as Inhibin-A.
The screen is essentially the same as the screening tests that look for only three substances, except the likelihood of identifying pregnancies at risk for Down Syndrome is higher through the evaluation of Inhibin-A levels. The false positive rate of the test is also lower.
What is a screening test?
It is very important to remember what a screening test is before getting one performed. This will help alleviate some of the anxiety that can accompany test results. Screening tests do not look only at results from the blood test. They compare a number of different factors (including age, ethnicity, results from blood tests, etc…) and then estimate what a person’s chances are of having an abnormality.
These tests DO NOT diagnose a problem; they only signal that further testing should be done.
How is the quad screen test performed?
The quad screen test involves drawing blood from the mother, which takes about 5 to 10 minutes. The blood sample is then sent to the laboratory for testing. The results usually take a few days to receive.
What are the risks and side effects to the mother or baby?
Except for the discomfort of drawing blood, there are no known risks or side effects associated with the quad screen test.
When is the quad screen test performed?
The quad screen test is performed between the 16th and 18th week of pregnancy.
All pregnant women should be offered the quad screen, but it is recommended for women who:
- Have a family history of birth defects
- Are 35 years or older
- Used possible harmful medications or drugs during pregnancy
- Have diabetes and use insulin
- Had a viral infection during pregnancy
- Have been exposed to high levels of radiation
What does the quad screen test look for?
The quad screen measures high and low levels of AFP, abnormal levels of hCG and estriol, and high levels of Inhibin-A. The results are combined with the mother’s age and ethnicity in order to assess probabilities of potential genetic disorders. High levels of AFP may suggest that the developing baby has a neural tube defect such as spina bifida or anencephaly.
However, the most common reason for elevated AFP levels is inaccurate dating of the pregnancy.
Low levels of AFP and abnormal levels of hCG and estriol may indicate that the developing baby has Trisomy 21(Down syndrome), Trisomy 18 (Edwards Syndrome) or another type of chromosome abnormality.
What do the quad screen results mean?
It is important to remember that the quad screen is a screening test and not a diagnostic test. This test only notes that a mother is at risk of carrying a baby with a genetic disorder. Many women who experience an abnormal test result go on to deliver healthy babies. Abnormal test results warrant additional testing in order to make a diagnosis.
A more conservative approach involves performing a second quad screen followed by a high definition ultrasound. If the testing still maintains abnormal results, a more invasive procedure such as amniocentesis may be performed.
Any invasive procedure should be discussed thoroughly with your healthcare provider and between you and your partner. Additional counseling and discussions with a counselor, social worker or minister may prove helpful.
What are the reasons for further testing?
The quad screen is a routine screening that poses no known risks to the mother or baby. The quad screen results may warrant additional testing. The reasons to pursue further testing or not vary from person to person and couple to couple.
Performing further testing allows you to confirm a diagnosis and then provides you with certain opportunities:
- Pursue potential interventions that may exist (i. e. fetal surgery for spina bifida)
- Begin planning for a child with special needs
- Start addressing anticipated lifestyle changes
- Identify support groups and resources
- Make a decision about carrying the child to term
Some individuals or couples may elect not to pursue testing or additional testing for various reasons:
- They are comfortable with the results no matter what the outcome is
- Because of personal, moral, or religious reasons, making a decision about carrying the child to term is not an option
- Some parents choose not to allow any testing that poses any risk of harming the developing baby
It is important to discuss the risks and benefits of testing thoroughly with your healthcare provider. Your healthcare provider will help you evaluate if the benefits from the results could outweigh any risks from the procedure.
Last updated: September 2, 2016 at 15:45 pm
Compiled using information from the following sources:
2. March of Dimes
3. Second trimester maternal serum screening for fetal open neural tube defects and aneuploidy”, American College of Medical Genetics Policy Statement (2004).
Pregnancy and the Quad Marker Screen
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The quad marker screen, similar to the triple marker screen, is a blood test that provides a woman and her health care provider with useful information about her pregnancy. The test predicts the Likelihood of a certain problem occurring. It does not diagnose the problem. For example, cholesterol screening determines a person’s risk for heart disease based on the amount of cholesterol in the blood, but it does not necessarily mean that the person has heart disease. The quad marker screen determines if a woman is at higher or lower risk of carrying a baby with a birth defect. This means that some women with healthy babies will have screening results indicating a possible problem (and will be offered appropriate follow-up testing), while some women whose babies have birth defects will go undetected.
Because of the uncertainties surrounding the test result, you can opt to not have it. Talk to your doctor about the pros and cons of taking this test before you make a final decision.
What Happens During the Quad Marker Screen?
During the quad marker screen, a sample of blood is taken from your vein. Substances in the blood sample are measured to screen for:
- Problems in the development of the fetus’s brain and spinal cord, called open neural tube defects; the quad marker screen can predict approximately 75%-80% of open neural tube defects.
- Genetic disorders such as Down syndrome, a chromosomal abnormality; the quad marker screen can predict approximately 75% of Down syndrome cases in women under age 35 and over 80% of Down syndrome cases in women age 35 years and older.
When Should I Get a Quad Marker Screen?
Between 15 and 20 weeks of pregnancy, your health care provider may offer you a quad marker screen. The test can only be performed during the 15 th and 20 th week of pregnancy.
What Substances Are Measured During a Quad Marker Screen?
The blood sample is sent to a laboratory and tested for the presence of the following four substances, which are normally found in the baby’s blood, brain, spinal fluid, and amniotic fluid:
- Alpha-fetoprotein (AFP): A protein produced by the baby’s liver and other organs
- Unconjugated Estriol (UE): A protein produced in the placenta and in the baby’s liver
- Human Chorionic Gonadotropin (hCG): A hormone produced by the placenta
- Inhibin-A: A hormone produced by the placenta
The expected amount of these substances normally found in the mother’s bloodstream changes weekly during pregnancy, so it is important to tell your health care providers how far along you are in your pregnancy. High AFP levels may indicate that the baby has an open neural tube defect. High AFP levels may also indicate that the fetus is older than was thought or that the woman is expecting twins. Lower than normal AFP levels could indicate that a woman is at higher risk for having a baby with Down syndrome.
Levels of hCG and Inhibin-A are higher than normal when a woman has an increased risk of having a baby with Down syndrome. Lower than normal levels of estriol (a hormone) may also indicate that a woman is at high risk for having a baby with Down syndrome.
Is the Quad Marker Screen Safe?
Yes. The quad marker screen is a safe and useful screening test for families concerned about birth defects or genetic diseases. It is a test that carries no risk to the baby, since a blood sample is taken only from the mother.
What Does It Mean if the Quad Marker Screen Results Are Normal?
Normal levels of AFP, estriol, hCG, and Inhibin-A strongly indicate that you have a healthy pregnancy and a healthy baby. In over 98% of pregnancies, normal quad marker screen results predict healthy babies and births without major complications. However, there are no prenatal tests that can guarantee your baby and pregnancy will be completely healthy or without complications.
What Does It Mean if the Quad Marker Screen Results Are Abnormal?
Quad marker screen results that are not in the normal range do not necessarily mean there is a problem in your pregnancy.
The quad marker screen is used as a screening tool only, which means it can only assess your risk of having a baby with a certain birth defects (it is not used to diagnose the particular problem that may be present). If the quad marker screen results are not in the normal range, further tests such as an ultrasound or amniocentesis may be necessary.
Out of 1,000 pregnant women, approximately 50 will have quad marker screen results that indicate an increased risk for having a baby with a birth defect. Of those 50 women, only one or two will actually have a baby with an open neural tube defect. About 40 women will have quad marker screen results that show an increased risk for having a baby with Down syndrome and one or two will actually have a baby with Down syndrome.
Should I Have the Quad Marker Screen?
It is recommended that all pregnant women have a quad marker screen, but it is your decision whether or not to have the test. However, if you have any of the following risk factors, you may strongly want to consider having the test:
- You are age 35 or older when the baby is due
- Your family has a history of birth defects
- You’ve had a child with a previous birth defect
- You were diagnosed with type 1 diabetes prior to your pregnancy
If you have any concerns about the test, talk to your doctor or health care provider.
The March of Dimes.
Deborah A. Driscoll, MD, “Second trimester maternal serum screening for fetal open neural tube defects
And aneuploidy.” American College of Medical Genetics, 2004.
Quad Screen Test To Determine The Risk Of Carrying Genetic Disorders
One of the most important “maternal blood screening tests” is the quad screen test.
Four specific substances will be tested under this test.
They include: hCG (Human chorionic gonadotrophin), AFP (Alpha fetoprotein), inhibin-A and Estriol.
- HCG is a hormone that is created within the placenta.
- AFP is produced by the fetus.
- Inhibin-A is a protein which is produced by the ovaries and placenta.
- Estriol is an estrogen produced by the placenta and also the fetus.
This test is very similar to the triple screen test. The only difference is, in the quad screen test, the possibility of recognizing the risk of Down syndrome is higher with the evaluation of inhibin-A levels.
How is the quad screen test performed?
This test includes collecting a blood sample from the mother, which lasts for 5-10 minutes. This sample of blood is then tested in the laboratory and the results will be displayed within a few days.
During the test process, you will experience slight discomfort. Instead of this, there are no known dangerous consequences or risks associated with Quad screen test.
Usually, you will need to undergo this test procedure between the 16th-18th weeks of pregnancy. Most pregnant women are eligible for this test procedure, but women who should undergo this test procedure particularly include:
- Pregnancy after 35 years of age
- Suffering with diabetes and receiving regular dosage of insulin
- Exposed to high levels of radiation
- Having a family record of common birth defects
- Suffering from any form of Viral infection during pregnancy
- Taken harmful drugs or medications during the pregnancy period
Benefits of quad screen test:
This test is useful to measure high or low AFP levels, high levels of inhibin-A, and Abnormal levels of estriol and hCG. These results are included with your age and background to identify the possibilities for dangerous genetic disorders.
If the test confirms high AFP levels, then your baby is at a risk of neural tube defects like anencephaly or spina bifida. The most common cause for high AFP levels is incorrect dating of pregnancy.
Abnormal hCG and estriol levels and low AFP levels indicate that your baby has the possibility to develop Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18) or various other chromosomal abnormalities.
Remember that the quad screen test is a type of screening method, but not a diagnostic method. This method only shows whether you are carrying at a risk of genetic disorders.
If the test shows abnormal results, then your practitioner recommends for high definition ultrasound. However, if the test gives abnormal outcomes, then a more invasive method called amniocentesis test is recommended. However, before undergoing the test procedure once, discuss it with your doctor.
Http://www. momjunction. com/articles/triple-screening-in-pregnancy_00395779/
Http://www. webmd. com/baby/quad-marker-screen
Http://www. thepregnancyzone. com/tests-and-procedures/quad-screen-test-to-determine-the-risk-of-carrying-genetic-disorders/