Q.,1:-,, What
is the quad marker screening test?
The quad marker screening test (quad screen) is a blood test done in pregnancy, between the 15th and 20th weeks
of gestation. Similar to the triple screen, the quad marker screen provides information
about whether there is an increased risk for certain birth defects in the foetus like risk
for neural tube defects and certain
chromosomal abnormalities, like Down syndrome
The
quad marker test is a screening test
like NT Scan & Double marker (serum tets). His is not a diagnostic test,. ,
The quad marker screening test (quad screen) is a blood test administered
in pregnancy, typically between
the 15th and 20th weeks of gestation. Similar to the triple screen, the
quad marker screen provides information about whether there is an increased
risk for certain birth
defects in the baby.
Q.2:
Why is quad marker screening important during pregnancy?
Ans:-The test is noninvasive (a kind
of blood test) and involves taking a blood sample as for any other routine
blood test. The quad marker
test is a screening test, meaning that it gives information about risk,
but it does not allow the definitive diagnosis of any conditions. It can only
signal that further testing should be done to confirm a diagnosis.
Q. 3: The quad screen estimates four
substances. In addition to earlier test as
used to be measured in the triple screen
(alpha-fetoprotein, human chorionic gonadotropin, and estriol) Quad serum marker also includes one additional
substance, inhibin A.Of note that
·
2) Human chorionic gonadotropin
(hCG) is a hormone made by the placenta
·
4) Inhibin-A is another hormone made
by the placenta
Looking at levels of these four
substances in the mother's SERUM A STAISTICAL ANLYIS IS POSSIBLE BY SPECAL
SOFTWARE and allows an estimation of
risk for neural
tube defects and certain chromosomal
abnormalities, like Down
syndrome.
It all depends on dating USG for
week wise statistical risk calculations.. As mentioned earlier this test is a
screening test only, and is not 100% accurate. It can predict about 85% of open neural tube defects, problems with the development
of the baby's brain and spinal cord. It predicts about 80% of fetuses with Down
syndrome in women over age 35 and about 75% in younger women.
The fact that it is not 100% accurate means that not all
women who have a positive high risk result on the quad screen will have a fetus
with a birth defect and reverse vis also
true. That is the test may also be
normal even in the presence of birth defects.
For example, about 50 women out of
every 1,000 will have a result on the quad screen that indicates an increased
risk of a birth defect, but only one to two of those women will actually have a
baby with an open neural tube defect. About 40 women out of 1,000 will have a
result indicating an increased risk of Down syndrome, but only one to two of
these women will have a baby with Down syndrome.
As with any screening test, an abnormal result
does not mean that the fetus definitely has a birth defect or genetic
condition. It only means that the blood levels of these four substances suggest
that a woman's risk is increased of having a baby with certain conditions. Women
who have a result suggesting increased risk are typically offered further
testing. This can include repeating the quad screen and/or having a high
definition ultrasound examination to look for signs of birth defects
or abnormalities in the developing baby. If this testing is abnormal, the
mother may be offered the choice to undergo amniocentesis. Amniocentesis involves withdrawing a sample
of amniotic fluid for genetic and chromosome testing, and it
can definitively establish the diagnosis of genetic and chromosomal problems in
most fetuses. Amniocentesis carries a small risk of miscarriage (fewer than 1% of fetuses tested
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