Definition
Atypical antibodies can form when the patient’s immune system has been exposed to blood group antigens that they do not have themselves. This can happen following a blood transfusion or a pregnancy.
Consequences:
- Clinical significance varies from insignificant to harmful if a patient is subsequently transfused with red cells (or platelets) that have the corresponding antigen.
- Can lead to delays in providing suitable blood components.
- In people of childbearing potential, this can cause complications with future pregnancies potentially leading to haemolytic disease of the fetus and newborn (HDFN).
Frequency
Common (≥1/100 to <1/10).
Reducing the risk
- People of childbearing potential are routinely transfused D-negative and K-negative red cells if they lack these antigens (as anti-D and anti-K antibodies are most likely to cause HDFN).
- Additional testing is done for patients requiring long term transfusion programmes.
- Avoiding unnecessary transfusion is the best way to reduce the risk of antibody formation.
Further information/ resources
'Blood Groups and Red Cell Antibodies in Pregnancy' NHSBT information leaflet
BSH Use of Anti-D Ig for the Prevention of Haemolytic Disease of the Fetus and Newborn guideline (2014)