Risks of red blood cell alloimmunization in transfusion-dependent ß-thalassemia in Oman: a 25-year experience of a university tertiary care reference center and a literature review.

BACKGROUND: ß-Thalassemia is a common hemoglobinopathy in the Arabian Peninsula. Red blood cell (RBC) transfusion is a cornerstone for its management, but can create significant challenges including RBC alloimmunization. Herein, we examine alloimmunization risk factors in Omani patients with transfusion-dependent ß-thalassemia. Existing literature is summarized. STUDY DESIGN AND METHODS: A retrospective review of all patients attending our center over 25 years was performed. Clinical and transfusion records were examined. Chi-square test was used to assess the association between the categorical variables. Nonparametric Mann-Whitney test was used to assess the association between transfusion and risk of alloimmunization. RESULTS: A total of 268 patients were identified (168 adults and 100 pediatrics), of whom 226 are alive (84.3%). Males accounted for 53.4%. The cohort had a median age of 22 years (range, 2-43 years). The most common blood group was O+ (39%). The prevalence of alloimmunization was 9.3% with anti-E (24%) and anti-K (24%) being the commonest antibodies identified. There was a significant association between age and alloimmunization, with 68% of alloimmunized patients in the age group of 19 to 30 years (p < 0.01). Among adults, there was a significant association between alloimmunization and number of units transfused (p = 0.001). There was no association between alloimmunization and sex or history of splenectomy. CONCLUSION: Our study shows an association between alloimmunization and the age of the patients and number of units transfused. Transfusion support of this group of patients necessitates the availability of needed expertise and blood bank facilities.

Successful management of severe hemolytic disease of the fetus due to anti-Jsb using intrauterine transfusions with serial maternal blood donations: a case report and a review of the literature.

BACKGROUND: The management of pregnant women with anti-Jsb is challenging due to the paucity of antigen-negative blood for fetal and neonatal transfusion. CASE REPORT: A 29-year-old woman with anti-Jsb was referred for assessment of recurrent fetal losses. With the presence of the sister as a historically matched donor, she was planned for active surveillance for fetal anemia during pregnancy. STUDY DESIGN AND METHODS: The fetus remained well until 21 weeks of gestation when signs of fetal anemia and early hydrops fetalis were noted. Anti-Jsb titer was at 128. The sister's red blood cells (RBCs) were cross-match incompatible. Urgent intrauterine transfusion (IUT) was performed with washed irradiated maternal RBCs, donated after cessation of heparin. The mother was given intravenous iron (IV-Fe) and continued on weekly recombinant human erythropoietin (rHu-EPO). RESULTS: Repeated IUTs were needed every 1 to 3 weeks. Throughout a 7-week period, three maternal donations were performed with total donated whole blood volume of 1250 mL, supporting four IUTs. At 29 weeks of gestation, the procedure was complicated by umbilical cord hematoma necessitating urgent cesarean section. A male newborn was delivered, transfused at birth, and subsequently treated with phototherapy and five top-up transfusions. CONCLUSION: This case represents a successful example of managing hemolytic disease of the fetus due to a rare antibody using maternal blood. It also supports previous data on safety of maternal donations during pregnancy and the use of combination of rHu-EPO and IV-Fe as a supportive measure.

Transfusion therapy and alloimmunization in Thalassemia Intermedia: a 10 year experience at a tertiary care university hospital.

BACKGROUND: Thalassemia Intermedia (TI) has a wide clinical profile with many patients requiring only occasional transfusions. To prevent alloimmunization, we adopted a policy of issuing phenotype matched red blood cells in 2009. We examined transfusion indications and alloimmunization rate in TI patients. STUDY DESIGN AND METHODS: Clinical and blood bank records of 37 TI patients were reviewed. RESULTS: 23 Patients required transfusion for pregnancy (26), splenectomy (8) and anemia (11). Since 2009, total of 335 units were transfused with only one antibody developing after transfusing a non-phenotype matched unit. CONCLUSION: The commonest indication for blood transfusion was pregnancy. Providing phenotype matched blood has successfully reduced the rate of alloimmunization.

Prevalence of Red Blood Cell Major Blood Group Antigens and Phenotypes among Omani Blood Donors.

OBJECTIVES: Most literature on the frequencies of red blood cell (RBC) phenotypes are published in Europeans and Africans countries, with the frequencies in the Omani population unknown. We sought to determine the prevalence of RBC blood group phenotypes among Omani blood donors. METHODS: Blood group ABO, RhD type, and phenotyping were performed for 21 blood group antigens on enrolled blood donors. The following antigens were assessed serologically: Rh (C, c, E, e), Kell (K, k, Kpa, Kpb), Kidd (Jka, Jkb), Duffy (Fya, Fyb), Lewis (Lea, Leb), Lutheran (Lua, Lub), MNS (M, N, S, s), and P1. RESULTS: A total of 337 Omani blood donors were tested. The most common blood group was O+ (44.9%). Among the tested blood donors studied, 89.3% were RhD positive with R1r being the most common Rh phenotype. The k antigen was found at a frequency of 99.4%, while 4.5% of the blood donors studied were K+. The most common phenotype in the Duffy blood group system was Fy(a-b-), while the most common phenotypes in the Kidd and MNS blood group systems were Jk(a+b+) and M+N-S+s+ at 47.0% and 22.6%, respectively. The Le(a+) and Le(b+) antigens were found in 21.7% and 67.3% of the blood donors, respectively. One Jk(a-b-), one Le(a+b+), and two Lu(a-b-) individuals were identified. CONCLUSION: This is the first study to examine the frequencies of RBC phenotypes among the Omani blood donors. The study's results show Duffy blood group frequencies that resemble what has been reported in the African population, and higher frequencies of the rare null phenotypes compared to European populations.

Intrauterine Fetal Blood Transfusion: Descriptive study of the first four years' experience in Oman.

OBJECTIVES: Haemolytic disease of the fetus and newborn (HDFN) causes hydrops fetalis. The successful treatment of HDFN has been reported with intrauterine blood transfusion (IUT). This study aimed to describe the initial experience with IUT procedures in Oman. METHODS: This retrospective observational study took place at the Royal Hospital and Sultan Qaboos University Hospital Blood Bank, Muscat, Oman, and included all women who underwent IUT procedures in Oman between March 2012 and March 2016. Gestational and neonatal outcomes were assessed, including complications, morbidity, neurodevelopmental sequelae and mortality. RESULTS: A total of 28 IUT procedures for 13 fetuses carried by 11 women were performed. Gestational age at the time of referral ranged from 13-30 weeks, while the median gestational age at first IUT procedure was 26 weeks (range: 19-30 weeks). Indications for the procedure included HDFN caused by anti-D (n = 6), a combination of anti-D and anti-C (n = 4), anti-K (n = 1) and anti-Jsb (n = 1) antibodies and nonimmune hydrops fetalis due to a congenital parvovirus infection (n = 1). Median fetal haemoglobin levels at the beginning and end of the procedure were 4.6 g/dL and 12.8 g/dL, respectively. Most procedures were transplacental intravascular transfusions through the placental umbilical cord root (71.4%), followed by transamniotic intravascular transfusions (14.3%). The overall survival rate was 61.5%, with five deaths; of these, four were intrauterine and one was an early neonatal death due to non-resolved hydrops and severe cardiac dysfunction. CONCLUSION: As a relatively novel obstetric procedure in Oman, IUT seems to result in a favourable outcome for hydropic fetuses.