ABO Blood Type Test in Arizona

What this test measures

Blood type is determined by antigens, which are proteins and sugars on the surface of red blood cells. The ABO system has four main groups based on which A and B antigens are present. Type A has the A antigen, type B has the B antigen, type AB has both, and type O has neither. These antigens matter because the immune system can react against blood cells that carry unfamiliar markers.

The Rh system is a separate group of antigens, and the most important is the D antigen. People who have it are described as Rh positive, and those who lack it are Rh negative. The test uses a blood sample, often collected in a tube with an anticoagulant, and the laboratory mixes the red cells with known reagents to see which antigens are present. Results are reported as a combined type, such as A positive or O negative.

Blood typing is commonly performed before a transfusion, during pregnancy, and before some surgical procedures so that compatible blood can be prepared if needed. Many people also order it simply to know their own type. The test is a laboratory determination and not a diagnosis, and a qualified healthcare provider can explain how your blood type relates to your care.