GTB in a blood test refers to Blood Group B Transferase, an enzyme involved in determining your ABO blood type. More specifically, it's the enzyme responsible for adding a galactose sugar molecule to the H antigen on red blood cells, thereby creating the B antigen and defining the Blood Group B.
Here's a breakdown:
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ABO Blood Group System: This system classifies blood based on the presence or absence of specific carbohydrate antigens (A and B) on the surface of red blood cells.
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H Antigen: A precursor molecule that both A and B antigens are built upon.
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Blood Group B Transferase (GTB): This is an enzyme, coded by a specific gene. Its function is to transfer a specific sugar, galactose, to the H antigen. If this enzyme is functional, then the individual expresses the B antigen. If an individual has GTB, they will either have Blood Group B, or Blood Group AB.
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The Blood Test's Role: When blood typing is performed, tests are conducted to determine the presence of the A and B antigens. The presence of the B antigen indicates the presence and functionality of GTB (in the absence of specific rare genetic variations).
In summary, the presence of GTB (indicated by the presence of the B antigen) is determined during a blood test to classify a person's ABO blood type as either B or AB. This is crucial for safe blood transfusions and organ transplants, as incompatible blood types can cause severe immune reactions.
