What are blood types, and why are they important?
The most important blood type classification systems are the ABO system and the
Rh system. A, B, AB, and O are the
blood types in the ABO system. Each type of blood in
the ABO system also has a positive or negative
Rh factor. For example, if you have "A+ blood," it
means your blood is type A in the ABO system and your Rh factor is
If you get blood in a transfusion that isn't the right
type, you may have a transfusion reaction. A mild transfusion reaction rarely
is dangerous, but you must get treatment quickly. A severe transfusion reaction
can be deadly.
How is blood collected?
Blood banks collect blood
from volunteer donors. Before they donate, volunteers must answer questions
about their current health, health history, and any diseases they may have been
exposed to through travel to foreign countries, sexual behavior, drug use, or needle sticks (such as from tattoos).
Only people who pass this survey are allowed to donate blood.
Donated blood is then carefully tested for certain diseases and to find
out the blood type. If there is any chance that the blood may not be safe to
use, it is thrown away.
Most blood that passes the tests is then
split into its components and sent out for use.
Blood and its
components can be stored or used for only a short time before they must be
thrown away. This is why blood banks are always looking for donors.