ABO, Rh

Blood typing is a common test when blood transfusions and tissue transplants are required, as well as during pregnancy. A blood type lab test identifies certain inherited substances (antigens) that may be present on the surface of red blood cells and classifies them into four common groups: A, B, AB, or O, and is known as the ABO system.

In addition, a second system, the Rh system, determines if the red blood cells are Rh-positive or Rh-negative. You are Rh-positive when you have the Rh factor. It is important to know both the ABO and Rh types in that a mismatch is capable of inducing an intense immunogenic reaction that can be fatal.