Red Blood Cell - IMProving trAnsfusions for Chronically Transfused Recipients

Inclusion Criteria (Aim #1): * Well-characterized transfusion-dependent form of SCD or thalassemia (including Hemoglobin E-thalassemia and sickle-beta thalassemia) on chronic simple transfusion therapy or partial manual exchange * On a regular simple RBC transfusion schedule, including partial manual exchange (i.e., 1-3 units scheduled every 2-6 weeks and on a minimum 6-month chronic transfusion trial; for partial manual exchange, the phlebotomy must be completed before the transfusion is started without a back and forth between rounds of phlebotomy and transfusion) * Seen at any participating domestic hub hospital (i.e., Columbia University Irving Medical Center/Morgan Stanley Children's Hospital of New York, Weill Cornell Medical Center/Komansky Children's Hospital, Boston Children's Hospital, Froedtert \& Medical College of Wisconsin/Children's Wisconsin, University of California San Francisco, Benioff Children's Hospital Oakland) or enrolled in the Brazil REDS-IV-P sickle cell disease cohort and seen at any participating Brazil hemocenter (i.e., Childrens Institute and Adult Clinics at Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo - HCFMUSP, HEMOAM - Amazonas, HEMOMINAS - Minas Gerais, HEMOPE -Pernambuco, and HEMORIO - Rio de Janeiro) Exclusion Criteria (Aim #1): * Institutionalization or imprisonment * Foster care * Weight \<11 kg Inclusion criteria (Aim #2): * Either included in Aim #1 (consented patient with SCD or thalassemia) or patient with pediatric oncologic diagnosis under care in a pediatric hematology/oncology service with anemia due to chemotherapy or primary/secondary hypo-proliferative bone marrow requiring a RBC transfusion (including HSCT) * \[In domestic study only\] Age ≤21 years old (many pediatric services include care of patients up to age 21, therefore the protocol will not limit by age but instead on whether they are seen in a pediatric service) * Planned transfusion of RBC from an aliquot or unit from a single donor * Seen at any participating domestic hub hospital (i.e., Columbia University Irving Medical Center/Morgan Stanley Children's Hospital of New York, Weill Cornell Medical Center/Komansky Children's Hospital, Boston Children's Hospital, Froedtert \& Medical College of Wisconsin/Children's Wisconsin, University of California San Francisco, Benioff Children's Hospital Oakland) or at any REDS-IV-P participating Brazil hemocenter (i.e., Childrens Institute and Adult Clinics at Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo - HCFMUSP, HEMOAM - Amazonas, HEMOMINAS - Minas Gerais, HEMOPE -Pernambuco, and HEMORIO - Rio de Janeiro). Exclusion criteria (Aim #2): * Institutionalization or imprisonment * Foster care * Current active auto-immune hemolytic anemia based on positive direct antiglobulin test (DAT) with laboratory evidence of hemolysis and increased transfusion requirement * \[In domestic study only\] Microangiopathic hemolytic anemia * Weight \<18 kg