Alloimmunization in transfused patients with constitutional anemias in Norway.

Objective: The status of red blood cell alloimmunization in patients with constitutional anemias including hemoglobinopathies is not known in Norway. The study objective was to investigate the impact of a strategy based on phenotype-matching for C, c, E, e, K, Jka, Jkb, Fya, Fyb, S and s on alloimmunization.

Methods: We reviewed transfusions of 40 patients retrospectively using the computerized blood bank management system and medical records; including diagnosis, age at start of transfusion therapy, gender, number and age of packed red blood cell units transfused, follow-up time, phenotypes of the donors and patients, antigen-negative patients exposed to antigen-positive packed red blood cell units, transfusion reactions and alloantibody specificities.

Results: Forty patients received 5402 packed red blood cell units. Alloimmunization frequency was 20 % for the whole group, being 7%, 25 % and 30 % in patients with sickle cell disease (n = 14), thalassemia (n = 16) and other conditions (n = 10), respectively. The alloantibodies detected were anti-E, -c, -C, -Cw, -K, -Jka and -Lua.

Conclusions: Good communication between the clinicians and the transfusion services is essential for successful management of patients with constitutional anemias. Providing full phenotype-matched units was not always possible. Extended pheno-/genotyping before the first transfusion and providing antigen-negative units for antigen-negative patients for at least C, c, E and K in every red cell transfusion would probably have reduced the alloimmunization rate. Non-phenotype-matched transfusions seem to be the main reason for alloimmunization. Finding markers for identifying responders prone to alloimmunization will ensure targeted transfusion strategies.