Provision of blood products for the highly immunized patient

Abstract

Introduction: Rarely, in the pre-transfusion compatibility testing of patients requiring blood transfusion, a complex serological picture involving alloimmunization presents. Often this is found in patients with exposure to blood through transfusion or pregnancy. Patients who have received many transfusions are more likely to have higher rates of alloimmunization. Patients with autoantibodies with complex serology often need testing to insure no underlying antibodies to common antigens are present. There are several ways to define highly immunized; one way is the relative frequency of the desired blood type in the population. Alloimmunization to a high prevalence antigen or if multiple antibodies to common antigens are present, the frequency of that type may be quite low. The serological red cell antibody detection methods vary in sensitivity. Once the antibody identification is complete, the determination of clinical significance is vital. If an antibody is clinically significant, then the search for the blood commences. Various sources may be explored; autologous, family siblings, or allogeneic. Provision of these products in the volume needed is critical to meet patient needs. The patient population exposed to blood products from various sources are commonly represented in the highly alloimmunized patient population. Diagnoses in this group often include Sickle Cell Anemia and Beta Thalessemia. Sometimes autoimmune hemolytic anemia may be represented if the autoantibody is to a rare antigen or there are many underlying alloantibodies. The definition of highly immunized and the specificity of the contributing antibody specificities varies in countries. Globally, some blood types considered rare in some countries are not rare in others (example Fy(a-b-) in Asian countries compared to USA). In addition, a patient with a combination of antibodies to common antigens (for example, anti-e anti-s, anti-Fyb and anti-Jka) may define a rare type. Antibody detection methods vary. It is obvious that a saline detection method will be less sensitive than a Gel method. Also, if the reagent red cells used in the detection phase not diverse enough, it may not detect all alloantibodies. Molecular methods are commonly employed in partial D and e cases. If products are not easily attainable, it may be helpful to determine the clinical significance. Many use the rule of requiring reactivity at 37C for clinical significance. Others may rely solely on the specificity and still others utilize the Monocyte Monolayer Assay. Finding the blood may be a challenge. Autologous blood may be considered, especially in times of future surgical need or in pregnancy. Family members may be valuable. Allogeneic donors are generally found in Blood Centers who make it a priority to collect and store rare donor units. When the blood is not available domestically, international requiest may be required to meet the blood needs of the patient.