The Laboratory of Immunohematology & Genomics screens blood samples to identify donors whose
RBCs lack a high prevalence antigen. Once identified, the donor is assigned the
rare donor group identifier, which is known as Code 99.
Pertinent information is entered in the computer and a hard copy of the record
is forwarded to Special Donor Services Department who maintains and monitors the
future contact of these rare donors. Future RBC donations of these donors are
sent directly to a patient in need or to the Frozen Laboratory for preservation
until needed by a patient.
These rare types can be unique to each specific ethnic background. Donor samples
are tested for special antigens based on their ethnicity. A unit of blood is considered
rare when more than 200 donors have to be screened to find 1 suitable donor.
Completely typed antigen-negative units (referred as Code 96) are provided by
the Testing Laboratory to the Laboratory of Immunohematology to be issued for
patients with red cell antibodies. These donors are referred as precise-matches
to patients who have developed red cell antibodies. These donor units are not
only typed for ABO but also typed for the antigens of the following blood group
systems: RH, K, FY, JK, Ss. They are categorized according to their Rh phenotype
(R1R1, R2R2, RoRo and rr.) and lack different combinations of blood group antigens.