How Does Blood Typing Work?


Quick Answer

Blood typing, which is the process of determining an individual's blood type, works by identifying the antigens, or proteins, in the sample's red blood cells. The different blood types are A, B, AB and O in the ABO blood typing system.

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Full Answer

Blood typing requires taking a simple blood sample from a vein, as MedlinePlus explains. After drawing the blood, the lab technician combines the blood sample with certain antibodies, including type A and type B blood antibodies to see if the blood cells stick together. If they do, it indicates that the blood is reacting with the antibodies, which identifies what the blood type is.

After the first stage of the test, the technician combines the liquid substance from the blood sample that doesn't contain any cells with type A or type B blood in a process known as back typing to look for additional antibodies in the blood. Type O blood has both types of antibodies, as MedlinePlus details. Type A should have anti-B antibodies, while type B has anti-A antibodies.

In addition to checking the individual's blood type, this process also looks at the Rh factor in red blood cells, as noted by MedlinePlus. The presence of Rh factor in the blood means that the person is Rh positive, while if none is present, the person is Rh negative. In both cases, the information helps medical personnel identify what blood they can use if the person needs a blood transfusion, and it can also help with transplants.

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