Blood typing and isoimmunization Flashcards
Alleles encode specific cell membrane Carbohydrates or proteins on RBCs called _____
antigens
Antigens/Agglutinogens are
_____ on the surface of the
RBCs and can cause agglutination
(clumping) of RBCs during transfusions
carbohydrates
_____ – gamma globulins produced in the lymph and bone
marrow, IgG “antibodies”
Agglutinins
At birth, the quantity of agglutinins in the
plasma is essentially _____
zero
____ months after birth, infants will begin
to produce agglutinins
2-8
Peak titer of agglutinins is at ____ yo
8-10
From birth, we are exposed to “A-like” and “B-like” carbohydrate
antigens from a variety of sources – _____. What occurs from this?
Food, bacteria, other substances
As a result, we develop antigen-specific “natural” IgG and IgM immunoglobulins even in the absence of blood transfusions
Relative Frequency of Different Blood Types
● O – 47%
● A – 41%
● B – 9%
● AB – 3%
A and B show ____
co-dominance
There are ____ different types of Rh antigens (called Rh Factors)
six
The ___ antigen is widely prevalent and considerably more antigenic than the other Rh Antigens
D Antigen
“____” if the D antigen is absent
Rh-
“____” if the D antigen is present
Rh+
______ (or alloimmunization) is when our bodies have an immune response to nonself antigens from members of the same species
Isoimmunization
Universal recipient
AB
Universal Donor
O
During subsequent pregnancies, the mother’s anti-Rh agglutinins cross the
placenta to an Rh-positive fetus resulting in various forms of ______ (Hemolytic Disease of the Newborn)
Erythroblastosis Fetalis
Erythroblastosis Fetalis (hemolytic disease of the newborn) causes _____
○Anemia:Results in over production of erythroblasts from the bone marrow
○Jaundice: With significant buildup of bilirubin may result in Kernicterus – neurologic syndrome when unconjugated
bilirubin is deposited in the basal ganglia
○ Hydrops fetalis: Hepatosplenomegaly, ascites, edema, pleural/cardial effusion
○ Death
______ – neurologic syndrome when unconjugated bilirubin is deposited in the basal ganglia
Kernicterus
Prevention for Erythroblastosis Fetalis
RhoGAM - Rh(D) Immunoglobulin Globin
(Anti-D Antibody)
○ Given to the mother IM at 28 to 30
weeks gestation and 72 hours
postpartum
RhoGAM MOA
In an RhD-negative individual
RhoGAM suppresses the immune
response and antibody formation
of RhD-positive red blood cell
RhoGAM Indication
D-negative mother with a fetus that is, or may be, D-positive
■ An RhD-incompatible pregnancy is assumed
● If the fetus/baby is either RhD-positive or RhD unknown or if the father is either RhD-positive or RhD
unknown.
● Use is not needed if the father or baby is conclusively RhD-negative.
RhoGAM contraindications
○ History of anaphylaxis or severe hypersensitivity reaction to human
immune globulin
○ Autoimmune hemolytic anemia
○ Hemolysis, pre-existing or at high risk
○ IgA deficiency with antibodies against IgA; potential for severe
hypersensitivity & anaphylactic reactions
RhoGAM Side effects
○ Injection site pain (0.5% )
○ Nausea (0.7% )
○ Extravascular hemolysis (Mild) (21% ) → low hemoglobin
○ Dizziness (0.5% )
○ Headache (0.5% to 14.3% )
○ Malaise (0.5% )
● Pregnancy: Category C
● Breast Feeding: Minimal risk
RhoGAM adverse effects
○ Hematologic: Intravascular hemolysis
○ Immunologic: Anaphylaxis (rare)
○ Renal: Renal failure, acute
RhoGAM monitoring
○ Suppression of Rh isoimmunization; Rh-positive red cell clearance is indicative of
efficacy
○ If used for pregnancy - observed for about 20 minutes following administration
○ If used for ITP - observed for 8 hours following administration, UA, CBC baseline
and following administration
_____ – Testing for antibodies in the serum
Indirect Coombs Test
Type and Cross (Crossmatch)
● Testing to determine if the donor’s and recipients blood are compatible
● ABO and Rh first confirmed, then blood from the donor and recipient
are mixed in a test tube
○ Detects antibodies to other blood group systems
○ Detects antibodies in low titers/those that do not agglutinate easily
Type and Screen
● ABO and Rh antibody screen – determination of blood type
● Indirect Coombs Test – Testing for antibodies in the serum
Final step prior to transfusion
Type and Cross (Crossmatch)
When to Order type & screen vs crossmatch
● Type & Screen
○ Type – ABO and Rh status
○ Screen – Screens patient’s blood for antibodies to other antigens
○ Order if there is any chance that the patient may require blood
● Crossmatch
○ Mixing donor and recipient blood to ensure compatibility
○ Detects antibodies in low titers/those that do not agglutinate easily
○ Order if there is higher risk of transfusion (ask the lab to put the
donation blood on hold)
○ More costly and takes longer (~45 min)
When to Order Uncrossmatched Blood
Order if you need stat blood. Call the lab and communicate that you need unmatched O- or O+ blood “stat”
