Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1157 page)

   Direct testing assesses only particular targeted mutation(s) of interest

   Linkage analysis, testing of a nearby genetic marker used when the particular mutation is unknown, is limited by potential recombination between the tested marker and the causal mutation.

   Mitochondrial DNA testing may be problematic because the mutated mitochondrial mutation is likely to exist in combination with normal mitochondria (heteroplasmy).

PRETRANSFUSION COMPATIBILITY TESTING
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   Definition and Use

   Demonstration of RBC antigen–antibody reactions is the foundation for pretransfusion compatibility testing and the key to immunohematology. Agglutination is the end point for most of these tests (including performing the blood type, the antibody screen, and the crossmatch). Increased genetic knowledge has added a new approach to red cell antigen typing using DNA sequence determination, but these tests are currently not being used for routine blood bank testing, and the tests described in this Chapter are based on the classical agglutination methodology.

   Three major requirements must be satisfied for safe RBC transfusions:

   The RBCs to be transfused must be ABO compatible

   RhD-positive RBCs should not be given to RhD-negative patients

   Transfused RBCs should lack blood group antigens to which the patient has preexisting clinically significant antibodies

   To achieve these objectives, pretransfusion compatibility testing begins with the type and screen, where the recipient’s ABO group and Rh (D) typing is determined. Antibodies to the ABO antigens are naturally occurring and are used to determine a person’s ABO blood group. Next, the patient’s serum is screened for the presence of clinically significant (non-ABO) antibodies directed against other blood group antigens. If an antibody is detected by the antibody screen, an antibody identification panel must be performed to identify the antibody.

   Safe transfusion can be ensured for most recipients by the correct ABO and Rh typing of patients and donors.

   ABO Group Determination