الفهرس 
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Abstract
Thalassemia syndromes are the most prevalent inherited single gene disorder in the world, it refers to a set of inherited autosomal recessive blood diseases accompanied by defective synthesis of α or β globin subunits of hemoglobin A (α2; β2).
Beta thalassemia is the result of decreased or absent formation of beta globin chains, leading to excess alpha chains. The main mark of the disease is the α-globin or β-globin chain imbalance causing ineffective erythropoiesis.
β-thalassemia is the most frequent genetically inherited hemoglobinopathy in Egypt, It had been estimated that 1000 children with thalassemia are born yearly out of 1.5 million live births and the carrier rate had been detected to be in the range of 6%-10%.
Beta thalassemia patients are classically classified to thalassemia major, intermedia or minor on the base of their α-globin or β-globin chain imbalance, clinical presentation and intensity of anemia.
Allogenic bone marrow or stem cell transplantation is the solely curative treatment for β-thalassemia major (severe form) which is out of reach for most of them. In the absence of transplantation, lifelong RBC transfusion is the mainstay of management for β thalassemia major patients which alleviate anemia and suppress compensatory mechanisms responsible for clinical disease.
Regular transfusion is usually given every 2-4 weeks to ensure normal growth and development during childhood and good quality of life in adults.
The formation of anti-red cell antibodies (allo and auto) stays a main problem in thalassemia patients. Red cell alloimmunization decreases survival time of transfused red cells, causes laboratory difficulties during RBC cross matching, delays safe transfusions provision, and might speed up iron overloading.
The aim of the present study was to determine the frequency of red cell alloimmunization among Egyptian transfusion dependent β-thalassemia children attending the Hematology Clinic of Alexandria University Children’s Hospital (at El-Shatby)
The current study was carried out on a total of 100 children aged 3-16 years. All patients were subjected to full history taking and clinical examination.
Transfusion and clinical records of all patients were reviewed for age at first presentation, age at initiation of transfusion therapy, transfusion interval, total number of red cell units transfused and diagnosis of β-thalassemia (hemoglobin electrophoresis and/or PCR if available).
Thorough clinical examination with emphasis on state of spleen was carried out.
The following laboratory investigations were carried out.
• Routine (CBC, Serum ferritin and liver functions)
• Alloantibody screening using panel of cells of antibody screening (DiaMed-ID Diluent 2) and DiaMed ID Gel system.
• Antibody identification using (DiaMed-Dia Panel) and DiaMed Gel cards.
The results of the present study revealed that eleven (11%) out of total 100 studied patients were alloimmunized. The total number of alloantibodies identified in these patients was 25. Two patients (18%) had only one alloantibody, six patients (54.5%) had 2 alloantibodies, one patient (9%) had 3 alloantibodies and two patients (18%) had more than 3 alloantibodies. The most prevalent antibodies belonged to Kell and Rh blood group systems (7 out of 25 each)
The present study showed a statistically significant increase in the mean age of the alloimmunized patients at the time of study. Alloimmunization rate was highest among age group 12-16 years (54.5%) followed by age group 6-<12 years (45.5%). There was no antibody formation in the age group 3-<6 years (0%).
In comparison between alloimmunized and non-alloimmunized patients, there was no statistical significant difference between the two groups regarding sex and the age at initiation of transfusion therapy, however the difference is significant regarding the duration of transfusion (years) and the number of packed red cell units received.
There was a significant (positive) correlation between frequency of alloantibody formation and duration of transfusion in years and number of packed red cell units received (r= 0.225, 0.247 respectively, P value <0.05).
No significant difference between alloimmunized and non-alloimmunized groups regarding splenectomy