Rhesus Typing

Blood typing is a test that determines a person’s blood type. The test is essential if you need a blood transfusion or are planning to donate blood. Not all blood types are compatible, so it’s important to know your blood group.

Your blood type is determined by what kind of antigens your red blood cells have on the surface. Antigens are substances that help your body differentiate between its own cells and foreign, potentially dangerous ones. If your body thinks a cell is foreign, it will set out to destroy it.

•       O: Type O individuals can donate blood to anyone, because their blood has no antigens. However, they can only receive blood from other type O individuals (because blood with any antigens is seen as foreign).
•       A: Type A individuals can donate to other type A individuals and type AB individuals. Type A individuals can receive blood only from other type A individuals and type O individuals.
•       B: Type B individuals can donate blood to other B individuals and AB individuals. Type B individuals can receive blood only from type B individuals and type O individuals.
•        AB: Type AB individuals can give blood only to other AB individuals, but can receive blood of any type.

Blood typing is done prior to a blood transfusion or when classifying a person’s blood for donation. Blood typing is a fast and easy way to ensure that you receive the right kind of blood during surgery or after an injury. If you’re given incompatible blood, it can lead to blood clumping, or agglutination, which can be fatal. Blood typing is especially important for pregnant women. If the mother is Rh-negative and the father is Rh-positive, the child will likely be Rh-positive. In these cases, the mother needs to receive a drug called RhoGAM. This drug will keep her body from forming antibodies that may attack the baby’s blood cells if their blood becomes mixed, which often happens during pregnancy.

No special preparation is needed for blood typing. If you think you might feel faint during the test, you may want to have someone drive you home afterward.

You will need to have your blood drawn in order to have it typed. Having your blood drawn carries very minimal risks, including:

•       bleeding under the skin (hematoma)
•       fainting or feeling lightheaded
•       infection at the puncture site
•       excessive bleeding

In order to determine your blood type, a lab technician will mix your blood sample with antibodies that attack types A and B blood to see how it reacts. If your blood cells clump together when mixed with antibodies against type A blood, for example, you have type B blood. Your blood sample will then be mixed with an anti-Rh serum. If your blood cells clump together in response to the anti-Rh serum, it means that you have Rh-positive blood. Your blood type can be determined in a matter of minutes. Once you know your blood type, you can donate blood and receive transfusions from donors in the compatible blood groups.