Transfusion medicine handbook

7. Adverse Effects of Transfusion

7.8 Delayed Haemolytic Transfusion Reaction

A delayed haemolytic transfusion reaction (DHTR) is one in which evidence of increased red cell destruction develops following a transfusion, usually after 1 - 28 days. The symptoms and clinical or laboratory signs are similar to AHTR but are usually less severe, often manifesting as an inadequate rise or unexplained fall in the post-transfusion haemoglobin. Whilst clinically significant DHTRs are rare and seldom fatal, they can cause additional problems for a patient who is already seriously ill.

DHTR occurs in a patient who has been immunised to a red cell antigen by an earlier transfusion or pregnancy. The level of antibody may be so low that it cannot be detected in the pretransfusion sample. After transfusion of red cells bearing the target antigen, a rapid secondary immune response boosts the antibody level so that, after a few days, transfused red cells bearing the relevant antigen may be rapidly destroyed. Antibodies of the Kidd and Rh systems are the most frequent cause of DHTR.