Patients who develop antibodies directed towards reagent red blood cell antigens of high and low prevalence are frequently addressed together due to their complex nature, necessitating advanced knowledge, additional resources, and heightened attention. To facilitate a more efficient evaluation of suspected high- or low-prevalence antigens, the following points offer guidance for the investigation.
Antibodies to low-prevalence antigens
- Low-prevalence antigens are antigens that occur in less than 2% of the population.
- Antibodies are rare due to the low chance of exposure to the corresponding antigen.
- Low-prevalence antigens are not usually found on the screen cell and antibody panels.
- 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-prevalence antigens include Cw, V, Kpa, and 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.
Antibodies to high-prevalence antigens
- High-prevalence antigens are antigens that occur in greater than 98% of the population.
- 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-prevalence antigen).
- Reactions with screen and panel cells will all be positive (same strength and same phase).
- Autocontrol will be negative.
- Difficult to find antigen-negative compatible blood.
- Examples of antibodies to high-prevalence antigens are anti-k, anti-Kpb, anti-Jsb, and anti-Lub.
If an antibody to either a high- or low-prevalence antigen is present, it may be difficult to identify and may require further testing in a reference blood bank.
