Blood is made up of red blood cells, white blood cells, platelets, and plasma. Markers called antigens are found on the surface of red blood cells, and differences in these markers are used to classify the various types of blood. There are thirty-five different systems of blood group classification. Currently, blood is primarily categorized according to its ABO group and the presence or absence of Rh factor. Types, A, AB, O, and B make up the ABO group, and each of these can be either positive or negative for Rh factor. For example, an individual may have A positive blood or A negative blood, or they might have O positive or O negative blood. The blood type a child has is determined by genetics. To determine the type of blood an individual has, doctors mix a patient’s blood sample with different substances to see how the blood reacts. Knowing a patient’s blood type is critical in cases of blood transfusion, organ transplant, or surgery. Blood typing tests are normally performed at birth, and patients are also tested for their blood type as part of the blood donation procedure.
The outline below describes the major blood groups in detail.
Type O blood lacks both A and B antigens. However, antibodies to both types A and B are present in the plasma of patients with type O blood. O negative blood is often considered the ‘universal donor’ type because it can be given to patients with any blood type. The latest research suggests while this is the case for most situations, O negative blood may not always be the best type for blood transfusions for certain patients. O negative blood is one of the rarest blood types in the U.S., and only an estimated seven percent of Americans have this type. Individuals with O negative blood can only receive blood that is also O negative. However, they can give blood to patients who are A positive or A negative, B positive or B negative, and AB positive or AB negative.
O positive blood is the most common blood type in the United States; approximately thirty-eight percent of the population in the United States has this type. Individuals with O positive blood can receive blood transfusions of either O positive or O negative blood, and O positive blood donations can be given to individuals who have A positive, B positive, or AB positive blood.
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