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CIRCULAR
List of All blood banks
Camp Permitted Blood Banks
Performance of GSCBT till Mar-2011
Performance of Blood Safety Programme
Posters
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Tests For Thalassaemia |
A
Simple blood test is the most effective test. Unlike many other genetic disorders
, which require complex and often expensive testing, b (Beta)Thalassaemia carriers
are the easiest gene disorder carriers to discover as their red blood will be microcytic
(smaller in size) and hypochromic (paler in colour). The test is called Haemoglobin
Electrophoresis.
TESTS DURING
PREGNANCY
1. The opportunity to test the foetus is first offered to
a couple when BOTH partners have been found to be Carriers and they then CHOOSE
to test the foetus and exercise an informed choice.
2. There are 3 tests available and they must be done at their
respective optimum time. These tests are different from the blood test used to determine
a Carrier. Chorionic Villus Sampling (CVS) Test is done at 10 weeks of pregnancy.
Fetal blood sampling is done between 18 - 20 weeks and the rarely done Amniocentesis
is between 14 - 18 weeks.
HOW DO THE TESTS DETERMINE
IF THE FOETUS IS AFFECTED?
The choice of which test to use is a very carefully considered
matter. However, if the mother has presented herself early in a pregnancy, Chorionic
Villus Sampling is the best test because of the ease of doing it and its acceptability
to the mother as it can be done earlier in the pregnancy.
1. Chorionic Villus Sampling (CVS) involves taking a small
sample of the developing placenta at 10 weeks of pregnancy. The placenta, which
is attached to the growing foetus by the umbilical cord, contains the DNA imprint
of the baby. The placenta and its position is first assessed by ultra sound. A sample
of the placenta is obtained either through the vagina or through the abdomen dependent
upon where the placenta is located. The sample of placenta has its DNA then tested
to see if the child's Haemoglobin making genes are affected and this determines
if the baby has the full blown condition Thalassaemia Major.
2. Fetal blood sampling involves the taking of a blood sample
from the umbilical cord of the foetus in the womb. Fetal blood sampling is used
when the foetus has developed more and the pregnancy has advanced to 18 - 20 weeks.
An affected baby will have little or no adult Haemoglobin HbA. This test is used
when the CVS test cannot get access to the placenta or when the DNA test cannot
determine the exact DNA profile of the baby.
3. Amniocentesis involves taking a small sample of the amniotic
fluid that surrounds the baby (between 14 -18 weeks). As there are very few cells
from the baby floating about in the amniotic fluid, the test requires culturing
and growing of the captured cells in the laboratory and then the DNA of these cells
is tested as per the placenta test. |
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