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, can cause complications with future pregnancies (potentially causing 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 on patients who need to go on to long term transfusion programmes.
Avoiding unnecessary transfusion is the best way to reduce chances of antibody formation.
Further information/ resources
'Blood Groups and Red Cell Antibodies in Pregnancy' NHSBT information leaflet
Handbook of Transfusion Medicine: Prevention of haemolytic disease of the fetus and newborn (HDFN)