ABO Typing


ABO typing, serum or plasma and red cells (ABO)

Red or lavender/pink


Properly identified and labeled blood specimen is critical. A second “check” specimen is required.

Physiologic Basis

The ABO antigen and antibodies remain the most significant for transfusion practice.

The 4 blood groups A, B, O, and AB are determined by the presence of antigens A and B or their absence (O) on a patient’s red blood cells.

Individuals possess antibodies directed toward the A or B antigen absent from their own red cells.

In the US white population, 45% are type O, 40% A, 11% B, 4% AB. In the US Hispanic population, 57% are type O, 30% A, 10% B, 3% AB. In the African American population, 49% are type O, 27% A, 20% B, 4% AB. In the US Asian population, 40% are type O, 28% A, 27% B, 5% AB. In the Native American population, 55% are type O, 35% A, 8% B, 2% AB.


Type O patients can receive only type O red cells, and type A, B, O, or AB plasma. Type A patients can receive type A or O red cells and type A or AB plasma. Type B patients can receive type B or O red cells and type B or AB plasma. Type AB patients can receive type AB, A, B, or O red cells but only type AB plasma.

In an emergency situation, type O red cells and type AB plasma may be given to patients with any ABO blood type.


For both blood donors and recipients, routine ABO typing includes both red cell and serum testing, as checks on each other.

Tube testing is as follows: patient’s red cells are tested with anti-A and anti-B for the presence or absence of agglutination (forward or cell type), and patient’s serum or plasma is tested against known A and B cells (reverse or serum/plasma type).

Technical Manual of the American Association of Blood Banks, 18th ed. American Association of Blood Banks, 2014.