Low-incidence antigens are antigens that occur in less than 1% of the population.

Antibodies to low-incidence antigens

• Low-incidence antigens are not usually found on screen cell and antibody panels.

• Antibodies are hard to test for, but it is usually not difficult to find compatible blood.

• Suspect this antibody if an AHG crossmatch is incompatible and other causes have been ruled out, such as a positive donor DAT or ABO incompatibility.

• Examples of low-incidence antigens include: C^w, V, Kp^a, Js^a.

• When going through the process of Ruling Out, antibodies like anti-V, anti-C^w, anti-Lu^a, anti-Kp^a, and anti-Js^a usually fall into the "unable to rule out" category.

High-incidence antigens are antigens that occur in greater than 99% of the population.

Antibodies to high-incidence antigens

• Antibodies are rare and may be difficult to identify due to lack of negative panel cells for other high-incidence antigens (difficult to rule out).
• Reactions with screen and panel cells will all be positive (same strength and same phase).
• Auto control will be negative.
• Difficult to find antigen-negative compatible blood.
• Examples of antibodies to high-incidence antigens are: anti-k, anti-Kp^b, anti-Js^b, and anti-Lu^b.

If an antibody to either a high- or low-incidence antigen is present, it may be difficult to identify and may require further testing in a reference blood bank.