Extra Antigen Typings and Selection of RBC Units

Revision Date:  15/7/20 (replaces 9/6/20 post on Linked In and now recommends full extended Rh phenotype matching for sickle cell patients).

Principle:

Extended/extra antigen typing may mitigate alloimmunization in selected populations (chronically transfused such as sickle cell anemia, thalassemia, leukemias, lymphomas, etc.) and those patients already making RBC antibodies.  It can also help in discerning antibody specificities in patient workups where the antibody identification is unclear.  This policy is in addition to the current selection of antigen-negative RBCs when clinically significant antibodies are present (e.g. Kell-negative RBCs for patients with anti-Kell).

Policy:

  1. Perform extended Rh/Kell typing (CcEeK) in the following cases:
    1. Patient has a positive antibody screen during routine testing (unless typing has been previously performed and is showing in Medinfo Hematos IIG)
    2. All patients with hematopoietic neoplasia or related conditions: leukemias, lymphomas, myelodysplastic states, myeloproliferative states (polycythemia rubra vera, primary thrombocythemia, agnogenic myeloid metaplasia/myelofibrosis), aplastic anemia
    3. All patients with sickle cell anemia, thalassemia, sickle-thalassemia
  2. Selection of Donor Units in these situations:
    1. Match R1R1 when possible
    2. Match K-negative for K-negative patients
    3. Match rr for females <50 and children < 18 years
    4. There is no need to routinely match R1r, R2r, Ror, R1R2, or R2R2 genotypes with theses corresponding donor types except for sickle cell patients (item #5)
    5. Match exactly extended Rh phenotype and Kell for sickle cell patients (CcEeK): e.g. evenR2R2 for R2R2
  3. Hemolytic Disease of the Fetus/Newborn:
    1. If the neonatal eluate or mother at term shows a clinically significant antibody, phenotype the baby for the corresponding antigen (e.g anti-Fya  present, type baby for Fya)
  4. Extended antigen typing beyond Rh/Kell (e.g. k (cellano), Kpa, Kpb, Fya, Fyb, Jka, Jkb, MNSs, etc.) should be performed in the following cases:
    1. Sickle anemia, thalassemias, sickle-thalassemia
    2. Any antibody workup where the pattern is nonspecific
    3. Verify any antibody specificities by phenotyping the patient (e.g., if anti-M identified, do M typing)
    4. Cw phenotyping is not required unless anti-Cw is suspected.
  5. Genotyping may be considered if:
    1. Recently transfused patient and the extended typing is needed for antibody identification
    2. Ambiguous or unusual typing results (e.g. M-neg N-neg, lacking CcEe antigens by serologic typing)
  6. When NOT to phenotype:
    1. RBC transfusions within 3 months
    2. Previous phenotype in Medinfo Hematos IIG (unless the patient subsequently has had a stem cell transplant)
  7. Any other cases in which the Head, Transfusion Medicine or the other transfusion medicine physician requests additional typing.

Prepared By:

Zeyd Merenkov, MD, FCAP, FASCP

Senior Consultant/Division Head, Transfusion Medicine