Blood Transfusion Matching Criteria

Selection of Appropriate Units

• The ABO group of the recipient is the most important consideration for selecting donor units for transfusion.
• Donor units should be the same ABO group as the recipient, but if not possible, they must be compatible with the recipient's serum and must be given as packed RBC.
• Rh-positive recipients may receive either Rh-positive or Rh-negative blood units.
• Rh-negative recipients should only receive Rh-negative RBC, to avoid being sensitized to the D antigen.
• Group O negative RBC is the component of choice for neonatal transfusion.
• In emergency cases, if uncrossmatched blood is to be released, a Group O Rh-negative blood can be given, but compatibility testing should be performed as soon as possible.

Crossmatching

• A crossmatch is an antibody test on the serum of the patient using red cells of the donor as the test cell.
• Antibodies in the serum of the patient have different specificities, which are detected under a variety of different conditions.

ABO Blood Group System

• The ABO blood group system has four main groups: A, B, AB, and O.
• The antigen is present on the RBC surface and determines the blood group/type.
• The corresponding antibody is never found in the individual's serum.
• Naturally occurring antibodies are always present in the individual's serum.
• The percentage of naturally occurring antibodies in the American population is:
  • Anti-A: 40%
  • Anti-B: 10%
  • Anti-A and Anti-B: 45%
  • None: 5%

Forward and Reverse Grouping/Typing

• Forward blood typing uses known sources of commercial anti-sera (anti-A, anti-B) to detect antigens on a patient's RBC.
• Reverse blood typing detects ABO antibodies in the patient's serum by using known reagent RBC's (A and B cells).

Inheritance of the ABO Blood Group System

• The theory for the inheritance of the ABO blood groups was first described by Bernstein in 1924.
• The genes that code for the ABO blood type are located in the terminal portion of Chromosome 9.
• Each gene occupies a specific location on the chromosome called a locus.
• Each locus may have several different forms of genes, known as alleles.
• The genotype refers to the actual notation of the actual genes inherited from the parents.

Detection of RBC-Antigen Antibody Reactions

• Agglutination is the process by which particulate antigens such as cells aggregate to form large complexes when a specific antibody is present.
• Agglutination has two phases: sensitization and lattice-formation.
• Other types of agglutination reactions include:
  • Direct agglutination
  • Passive agglutination
  • Reverse passive agglutination
  • Coagglutination
  • Agglutination inhibition
  • Hemagglutination inhibition
  • Antiglobulin-mediated agglutination