Alloimmunization in Thalassemia Patients
Azita Azarkeivan, MD
Department of Thalassemia Clinic, Blood Transfusion Research Center, High Institute for
Research and Education in Transfusion Medicine, Tehran, Iran;
Thalassemia is the most frequent hereditary hemolytic anemia; these patients need
frequent blood transfusions . This treatment has some side effects: iron overload
and infections are the most frequent. Transfusion reactions also may occur as a
consequence of treatment. Acute and delayed hemolytic, allergic, and febrile
transfusion reactions are the immunologic basis reactions in part of blood
transfusion medicine .
Acute hemolytic reactions is due to ABO incompability between donor and
reciepient which may develop severe hemolytic reaction in few drops of
transfusion start time. Delay hemolytic reaction is because of minor blood group
incompatibilities (RBC Alloimmunization) and uasally hemolysis develop few
days after transfusion. Allergic transfusion is because of reaction to plasma
protiens by urticaria or rash after transfusion . Febrile blood reactions (temperature
elevation of 10C from body base line at the time of start transfusion ) usually are
caused by cytokines production during storage . Among these reactions ; delayed
hemolytic transfusion reaction is more important in chronic transfusion patients .
It is developed by producing antibodies against red blood cell (RBC) antigens that
the patient doesn’t have and these antigens may enter with repeated blood
transfusion( Alloantibody Formation) .
Genesis of alloantibodies is a fairly common condition in 0.2% to 38% of
population that differ based on studied groups and sensitivity of applied method .
Alloantibodies are mostly formed in response to incompatible blood transfusion,
fetomaternal transfusion, and rarely in transplantation or allogenic transfusion .
Thalassemia patients are one of the high-risk groups for alloantibody formation;
because of frequent blood transfusion , any incompatibility in transfused blood
units can cause formation of alloantibodies in this patient population and
subsequent complications .
The patient with delayed hemolytic transfusion reaction may present with jaundice
and fatigue, and decrease hemoglobin after transfusion . Sometimes these
antibodies may cause severe hemolytic anemia, which may need to use of
immunosuppressive treatment. Because blood transfusion in these patients is
necessary for life, early diagnosis and detection of these alloantibodies are very
important. Screening antibodies and identification can help detection of antigens
.There are some studies about use of gel method for better diagnosis of
alloantibody formation . Patients with defined alloantibody should be transfused by
antigen negative blood units.
In the most studies in transfusion reactions and RBC alloantibodies in thalassemic
patients ; alloimmunization were against Kell and Rh subgroups. . It means AntiRh(Anti- C ,c, E, e,D) and Anti-Kell antibodies are the most frequent antibodies in
thalassemia patients with chronic blood transfusions. So , RBC phenotyping
(specially Rh / Kell subgroups) and performing a careful cross match with
evaluating the blood group of a donated unit (especially for Rh subgroups and Kell
antigens) before
transfusion may be a useful tool in decreasing of
alloimmunization rate.
Keywords : alloantibody, alloimmunization, antibody screening, gel method
thalassemia, transfusion reaction