Immunohematology Quiz 2

• 85% of the US population is RH+. 15% are RH-
• Weak D or Partial D variations:

  • Weak D: Quantitative decrease in the amount of normal D
  • Weak D due to C: Occurs when Ce is on the other allele
  • Partial D: Lack of portions of the D antigen. Patients will make anti-D antibody when transfused with RH+ blood
  • Del: Near complete absence of normal D
• Weak D is tested for:

  • Infants to determine the need for RhoGam in an RH negative mother
  • Mothers before giving birth
  • Women of child-bearing age who appear Rh negative depending on your lab
  • All donor blood that is D negative on the immediate spin. If weak-D positive, must be labeled Rh positive
• C and c:

  • Codominant inheritance: If you have genes for both, you will express both
  • Less immunogenic than D
  • C is about 68% in whites; higher in Eastern Asians; lower in African blacks
  • c is about 80% in whites
• E and e:

  • Codominant
  • e is more frequent than E in all populations
  • E is more antigenic than e
• Antigenicity of Rh antigens:

  • One of the most antigenic blood group systems second only to ABO
  • Antigenicity from highest to least: D>c>E>C>e
• Rh immune globulin (RhoGam):

  • Administered to Rh negative moms carrying Rh positive babies
  • IgG anti - D
  • Administered at week 28 and after delivery or at the time of spontaneous/induced abortion
  • Binds the D cells so that the mother does not begin to produce her own IgG against the baby’s D cells
• Discuss how to collect blood for Immunohematology testing:

  • Provider generates requisition
  • Paperwork must have 2 independent identifiers
  • Tube must have at least 2 different identifiers, phlebotomist’s initials, date and time of the draw
• Acceptable specimen:

  • Plasma from Lavender top EDTA tube is preferred
  • Red tops can be used but are not preferred
  • Specimen should not be lipemic or hemolyzed
  • No contamination with IV fluid

  Do not relabel if you think there is an issue. Always redraw.

  WBIT (Wrong blood in tube) is the most common reason for ABO-incompatible transfusions
• Crossmatch and considerations for patients with antibodies:

  • IS crossmatch: mixing of donor cells with patient plasma
  • IAT crossmatch: tests patient plasma against antibody screening cells at multiple phases. Antibody ID is performed when the screen is positive
• Blood selection guidelines and blood administered in urgent situations:

  • If Rh testing cannot be performed, Rh negative blood is given
  • In emergency/urgent situations, the doctor weighs the risks of administering uncrossmatched blood
  • Group O blood is used if the ABO group is unknown
  • Rh negative blood is preferable for women of childbearing age if the Rh is unknown
• Fisher and Race: Rh system consists of three closely linked genes/alleles.

  Positive: DCe, DcE, Dce, DCE. Negative: dce (f), dCe, dcE, dCE
• • Weiner terminology: R = D, r = Absent D.
  • Positive: Dce = R0, DCe = R1, DcE = R2, DCE = Rz.
  • Negative: dCe = r’, dcE = r”, dCE = ry, dce = r
• • Rosenfeld 1962 nomenclature: D = Rh1, C = Rh2, E = Rh3, c = Rh4, e = Rh5
• In cases where there is either no sample, unacceptable sample, or non-agreement with patient’s history, type O must be issued.

  If Rh testing cannot be performed Rh negative blood is given.

  Selection: 

  -       1st: autologous unit, if available

  -       2nd: ABO/Rh compatible directed donor blood, if available

  -       3rd: allogenic units
• When patients are positive for a clinically significant antibody, transfusion units are tested against commercially prepared antisera and are antigen negative for the offending antibody
• Immunohematlogy tests can be:

  o   Stat: Emergency

  o   ASAP: Prioritize

  o   Routine: Like if a patient is coming for surgery in the coming month.
• The G antigen

  • It is a product of 2 RHD genes or the product of 2 RHCE-Ce genes
  • Therefore, red cells that are D or C positive are also G positive
  • Antibodies to G appear as anti-D and anti-C that cannot be separated
  • Biochemically, the expression of the G antigen depends on the presence of a common amino acid (serine) present on the surface of both D and C antigens