Overview
Red blood cells have different antigens on them. The main antigens of concern are the ABO and rhesus antigens.
ABO blood types
- Type A blood:
- A-antigens are present
- Anti-B antibodies are present due to no B-antigens being present
- Type B blood:
- B-antigens are present
- Anti-A antibodies are present due to no A-antigens being present
- Type AB blood:
- Both A- and B-antigens are present
- No anti-A or anti-B antibodies are present due to both antigens being present
- Type O blood:
- Neither of A- antigens or B-antigens are present
- Both anti-A and anti-B antibodies are present due to no A- or B-antigens being present
Rhesus types
Blood group is always done on pregnant people. If the pregnant person is rhesus negative and the neonate is rhesus positive, anti-rhesus antibodies may be made which can cross the placenta leading to haemolysis in the newborn.
- Rhesus positive – rhesus antigen present
- Rhesus negative – rhesus antigen not present
Reporting
Blood grouping is reporting based on ABO and rhesus status. A person with type A blood with rhesus antigens present has “A positive blood” – the ‘positive’ part refers to the presence of the rhesus antigens.
