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Biology and Genetics - Risk of Blood Transfusion

Blood transfusions are often a medical necessity.  The risks associated with transfused blood need careful consideration.

What exactly is blood?
Blood is made up of red and white blood cells, platelets, and plasma. Plasma is the fluid portion of the blood, the part you see, and contains proteins necessary for clotting as well as antibodies (immunoglobulins) that attack invaders (pathogens). Blood differs from person to person but we all fall into four categories (A, B, AB, O; divided into Rh Positive and Rh Negative types). Blood type is classified based on the presence or absence of antigens on the surface of red blood cells. Receiving the wrong type of blood is an obvious risk from a transfusion. However, donors’ blood may also present severe risks to the health of the recipients as blood can carry infectious diseases such as, and more insidious viruses like HIV and hepatitis C. 

Risks: Today the risks are minimal. Blood is routinely screened so that well-meaning donors are certified healthy. Blood is then tested before it is sent out for use. Blood needs to be processed and stored properly. It does have shelf-life.  Advances in blood storage are delivering better blood. And hospitals are practicing better tracking and delivering systems for blood products. These changes all point to a much better chance that the blood you receive will be helpful.*

Basic strategies designed to minimize the possibility that donated blood will turn out to be harmful to the recipient include: 

  • Screening of donors for risk factors prior to accepting a donation;
  • Testing all donated blood prior to use;
  • Good manufacturing processes;
  • Good administrative practices to reduce the risk of transfusing the wrong type of blood.


Thus, although the risks from a blood transfusion can never be reduced to zero, through the use of an interconnected series of risk control strategies, the risk from a blood transfusion today are very small.

*The agencies which administer the blood system in Canada, Canadian Blood Services and Héma-Québec, together annually collect over 1.2 million units of whole blood.  Individuals who suffer traumatic injuries or who are afflicted with diseases such as cancer, and those with inherited conditions such as thalassemia, an autosomal recessive blood disease, require either episodic or ongoing administration of units of blood as a matter of medical necessity.

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Contributor: William Leiss

Last reviewed: June 2, 2010

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