Antibody formation

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 and potentially causing haemolytic disease of the foetus and newborn (HDFN).

Frequency

Common (≥1 in 100 to <1 in 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 and resources

• NHSBT Patient information leaflets – see 'Receiving a blood transfusion' and 'Receiving anti-D immunoglobulin in pregnancy' leaflets