1Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea.
2Division of Hematology, Department of Internal Medicine, Catholic Blood and Marrow Transplantation Center, Leukemia Research Institute, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
A 26-year-old Emirati woman diagnosed with sickle cell anemia (SCA) in the United Arab Emirates (UAE) was admitted for allogeneic HSCT. According to her medical records from the UAE, she had a history of frequent admissions owing to sickle cell crisis, and had undergone a single RCE procedure in her country (Table 1). Her physical examination and laboratory data on admission are shown in Table 1. Her blood type was B+. The HbS level estimated by Hb electrophoresis (EP) was 70.8% of total Hb.
A 33-year-old Emirati man diagnosed with SCA in the UAE was admitted for allogeneic HSCT. According to his medical records from the UAE, he experienced frequent sickling crisis rashes with acute chest syndrome (Table 1), was admitted with painful crises and had undergone regular RCEs (Table 1). His physical examination and laboratory data on admission are shown in Table 1. His blood type was B+. HbS level was 64.5% and
A 26-year-old Emirati woman diagnosed with SCD in the UAE was admitted for allogeneic HSCT. According to her medical records from the UAE, she had a history of SCD-related complications including recurrent pain crisis and avascular necrosis of the left hip (Table 1). Her physical examination and laboratory data on admission are shown in Table 1. Her blood type was O+. HbS level was 89.3% of total Hb. In
RBC transfusion and RCE are among the main therapeutic modalities for both acute and chronic complications related to SCD, although allogeneic HSCT is considered a potentially curative therapy for SCD patients . Although simple RBC transfusion is easy to perform, automated RCE is shown to be efficient in reducing sickle cells without complications such as increasing a patient's blood volume and viscosity, and causing iron overload . According to the American Society for Apheresis (ASFA) , general guidelines for RCE in patients with SCD are end Hct of 30±3% to avoid hyperviscosity and HbS of 30% (or HbS+HbC of 30%). In adult patients with SCD, in preparation for non-myeloablative allogeneic HSCT, it is recommended that RCE be performed to reduce HbS levels to 30% or less . In the present study, final HbS levels in all 3 patients were less than 10% after 2 or 3 RCE procedures, demonstrating successful achievement of the target goal.
Most patients with SCD require chronic RBC transfusion, and thus are at high risk of alloimmunization. In patients with SCD, alloantibodies to the Rhesus system and to the K antigen account for over two-thirds of the RBC antibodies encountered in all populations studied. Alloantibodies to antigens in the Kidd, Duffy, Lewis, and MNS systems are also frequently formed in these patients. Anti-Lewis antibodies are usually clinically insignificant; however, the remaining antibodies formed by patients with SCD can potentially lead to hemolytic transfusion reactions and delays in finding compatible RBC units . Therefore, ABO, full Rhesus (D, C/c, E/e), and Kell antigen-matched blood should be recommended to prevent RBC alloimmunization . The RBC unit, which is HbS negative, leukocyte-reduced, and antigen-matched (C, c, E, e, K), is presented because long-term blood donor exposure can potentially increase the risk of infectious transmission and RBC alloimmunization . We used ABO-identical and leukocyte-filtered RBC units for replacement in all 3 cases. RBC units with full Rhesus antigen matching (with the exception of the K antigen) were used in the second RCE in Case 2 and all RCEs in Case 3. The Rhesus phenotypes of RBC units were provided by blood centers. Because the prevalence of the K antigen is extremely low in the Korean population , selection of replacement red cells without K antigen matching is not important. Our patients showed no evidence of new-onset RBC alloantibodies, and all successfully underwent HSCT. In Korea, the medical benefits of phenotyping of Rhesus systems (C/c and E/e) and other blood groups including Kidd and Duffy have limited application. The Korean Health Insurance Review and Assessment Service provides medical care benefits only for phenotyping hemolytic anemia patients with already formed alloantibodies and for phenotyping RBC units to find compatible units for these patients. This narrow extent of medical care benefits cannot cover phenotyping for prevention of RBC alloimmunization. Although Rhesus phenotypes (C/c and E/e) of RBC components were provided by blood centers including the Korean Red Cross and Hanmaum Blood Center, they recommend that the Rhesus phenotypes be confirmed in clinical laboratories when RBC units are issued for Rhesus-compatible transfusions. It has been reported that exact matching of RBC antigens including ABO, Rh, Kell, Kidd, and Duffy for transfusions in patients with SCD reduces the extent and rate of alloimmunization, providing safer transfusions in a timely fashion, and should be considered whenever such patients are transfused . Therefore, expanding criteria for blood group phenotyping is necessary to prevent RBC alloimmunization in patients likely to receive chronic transfusions, including patients with SCD.
To our knowledge, there are no reported cases of SCD in the Korean population, and there is only one case report of HbSβ0 thalassemia patient from Tunisia receiving prophylactic RCE in Korea before traveling back . Unlike in the previous report, we used RBC components with full Rhesus antigen-matching, which was found to be helpful in preventing RBC alloimmunization. In addition, all RCEs were performed as part of a preparative protocol for non-myeloablative allogeneic HSCT in patients with SCD. Therefore, this report will be helpful as more foreign patients come to Korea to undergo HSCT for the same reasons. In 2016, more than 2 million foreign residents including foreign workers, students, and intermarriage immigrants were living in Korea, constituting about 3.96% of the total population . As the number of foreigners increase annually, the need for understanding and managing a variety of diseases including SCD also increases. In this study, we report the cases of three Emirati patients with SCD who received successful RCE using the Spectra Optia system (TerumoBCT) for reduction of HbS prior to nonmyeloablative allogeneic HSCT. Our experiences demonstrate that automated RCE is an effective and safe therapeutic modality for rapid reduction of pathologic HbS in SCD patients over a short period.
Change of hemoglobin S (green bars) and Hct (red lines) levels of 3 SCD cases according to red cell exchange (black arrows).
Abbereviations: HbS, hemoglobin S; Hct, hematocrit; SCD, sickle cell disease; RCE, red cell exchange.