Low-incidence antigens are antigens that occur in less than 2% of the population.
Antibodies to low-incidence antigens
- Antibodies are rare due to the low chance of exposure to the corresponding antigen.
- 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: Cw, V, Kpa, Jsa.
- When going through the process of Ruling Out, antibodies like anti-V, anti-Cw, anti-Lua, anti-Kpa, and anti-Jsa usually fall into the "unable to rule out" category.
High-incidence antigens are antigens that occur in greater than 98% of the population.
Antibodies to high-incidence antigens
- Antibodies are rare due to the low number of antigen negative people in the population capable of producing the corresponding antibody.
- When present, rule out procedures will be difficult due to the lack of negative reacting panel cells (most if not all reagent cells will be positive for the high incidence antigen).
- 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-Kpb, anti-Jsb, and anti-Lub.
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.