Transfusion Biology Flashcards
Define blood group antigen
carb/protein present on surface of an RBC
Define RBC phenotype
combo of antigens on RBC surface
Define RBC genotype
genetic sequences at the loci for blood group antigens
Who is a universal recipient of blood
AB+
Who is a universal donor of blood
O-
Describe the presence or absence of Rh D antigen
- Rh+ if it is present (Can receive Rh+ OR Rh- blood)
- Rh- if it is not present (Can ONLY receive Rh- blood)
When is an anti-D alloantibody produced
When an Rh- person is exposed to small amounts of Rh+ cells (transfusion, pregnancy)
Describe the Bombay blood group
Can’t receive blood from A, AB, B, or O and ONLY from Bombay group
(can still donate blood)
Describe pre-transfusion testing
- ABO/Rh(D) typing: determines presence/absence of A, B, and Rh antigens on the patients RBCs
- Antibody screen: screens antibodies in plasma, done on everyone
- Compatibility testing/crossmatch: done when there is a high probability that the pt will need a transfusion & makes sure donor blood is compatible
Describe forward typing in ABO/Rh typing
test the patients RBCs for presence of A, B, and D antigens using antisera
Describe reverse typing in ABO/Rh typing
testing patients serum for presence of Anti-A, Anti-B, and Anti-D antibodies
Describe antibody screening by IAT (indirect antiglobulin test)
test for antibodies to common clinically significant RBC antigens
NOT a compatibility test, other Abs aside from ABO & Rh
What does a direct antiglobulin test screen for (DAT, Coombs)
used to detect Abs and/or complement on the surfaces of RBCs
- used in hemolytic anemia to detect auto/alloantibodies
What does an indirect antiglobulin test screen for (IAT, Coombs)
used to detect allo/autoantibodies in plasma or serum
- used in antibody screening for every pregnancy & compatibility testing before transfusion
If a crossmatch is negative, does that mean the blood product is compatible or incompatible with the patient?
compatible
Describe the 3 steps of pre-transfusion testing
- type (forward & reverse blood typing)
- screen (for antibodies)
- cross (identifying compatible blood product)
When is a type and screen done vs a type and cross
Type and screen
- just in case surgery is needed (minor surgery)
- doesn’t involve finding a compatible product
Type and cross
- transfusion likely needed or is needed (major surgery, trauma)
- does identify a compatible blood product
What special populations may be at greater risk when it comes to transfusion reactions
- infants <4 mos
- pregnancy
- sickle cell disease (w/ frequent transfusion hx)
- stem cell or organ transplant recipients
What non-antibody screening is done on blood products
Infectious agents
- HBV, HBC
- HIV
- Treponema pallidum
- Covid-19 Abs
- etc.
What are the major indications for packed RBCs (PRBCs)
- symptomatic anemia including acute blood loss (Hgb <8)
- asymptomatic w/ Hgb <7
- exchange transfusion in sickle cell pain crisis or hemolytic disease of a newborn
What do PRBCs do for us
- provide RBC mass and increase oxygen carrying capacity in the blood