Transfusion Medicine Flashcards
What does it mean when you get a type and screen?
- type: ABO blood, Rh type
- screen: IAT-indirect antiglobulin test for antibodies patient has against any blood group antigen
What is a crossmatch?
- done on donor blood before transfusion
- serum or plasma from patient’s blood tested with donor’s RBCs for agglutination or hymolysis
What does a direct anti globulin test (DAT) test for?
- detects IgG and/or complement that coats RBCs in vivo
- autoantibodies against own RBCs
- ordered to see if patient’s anemia is immune mediated
What does an indirect anti globulin test (IAT) test for?
-red cell antibodies that are unbound to red cells
What determines ABO blood type?
-ABO genes code for enzymes that modify H antigen on red cell surface to become A, B, or AB antigens. If H is unmodified, you are group O type.
What is fetal maternal ABO incompatibility?
-When mother is one blood group and fetus is a type that mother has circulating antibodies against. Anti A can be IgG and cross the placenta. But fetal RBCs only weakly express ABO antigens so not dire.
What determines rhesus antigens and what are the different types?
- encoded by RhD and RhCE multi pass proteins inserted into membrane by RHAG (rh associated glycoprotein)
- D antigen = Rh positive
- absence of D = d = Rh negative
- Also C,E, c, e antigens
- Weak D = single point mutation in RhD that encode intracellular regions, results in reduced # of D antigen sites. Don’t make anti-D
- D variants = point mutations in RhD on extracellular surface, alter and create new epitomes. D+ but can make anti-D
- Rh null = mutation in RHAG, cause RBCs devoid of Rh antigens, stomatocytosis, shortened RBC survival, can only receive transfusions from other Rh nulls bc of antibodies
- false D+ =crawford antigen, truly Rh- but tests +, common in African Americans
How can Rh hemolytic disease of the newborn occur?
- When mother is Rh negative and fetus if Rh positive
- And mother has anti-D through previous exposure to Rh+ (previous pregnancy, transfusion, IV drugs)
- mother must be treated with anti-D antibody to protect fetus from anti-D attacking its D antigen
What are the different types of platelet antigens?
- only on platelets: glycoprotein molecules HPA 1, 2, etc.
- on platelets and mononuclear cells: HLA class I antigens
- only platelets and RBCs: A, B, H, P, I and lewis antigens
Antibodies against which platelet antigens are commonly responsible for a number of diseases including autoimmune thrombocytopenic pupura?
platelet glycoproteins
What are the different types of human neutrophil alloantigens?
HNA system:
most important is HNA-3a
What is the difference between expected and unexpected alloantibodies? Which are the commonly expected and unexpected alloantibodies?
expected: are always found in an individual who lacks corresponding antigen.
- ABO antibodies
unexpected: typically found in small percentage of individuals, even though they lack corresponding antigen.
- rhesus, kidd, kell, duffy, Ii, Lewis, MNSs, P
What are the characteristics of ABO blood group alloantibodies? expected? unexpected? naturally occurring? Describe which blood groups can receive which ABO blood transfusions.
-expected, naturally occurring.
-O is universal donor (lacks A and B antigens), can only receive O blood
-A and B can receive from its own type and from O
-AB can receive from A, B, and O
anti A found in B indivs
anti B found in A indivs
anti A, B, and anti AB in group O
AB don’t express ABO antibodies
-antibodies formed can bind complement and cause intravascular hemolysis
What are the characteristics of Rh alloantibodies? expected? unexpected? naturally occurring? Describe which blood groups can receive which Rh blood transfusions.
unexpected, blood exposure stimulated
-do not bind complement, extravascular hemolysis
What are other important RBC antibodies besides ABO and Rh?
- Kidd system: anti-Jka, anti-Jkb
- Kell system: anti-K
- Duffy system: anti-Fya, anti-Fyb
Describe platelet antibodies and alloantibodies.
- anti-glycoprotein antibodies: unexpected and mostly autoantibodies
- anti-HLA antibodies: allo, unexpected, blood exposure stimulated. can be found with pregnancy, transfusion.
- ABO antibodies: allo, expected, naturally occurring. ABO incompatible platelets can still function, but best to transfuse identical platelets
What are important antibodies to consider when transfusing plasma?
-plasma given to patient who needs coagulation factors, e.g. trauma patients
-ABO antibodies: transfuse opposite of RBC
O group: will have antibodies to A and B antigen, can receive all groups, but can’t donate
AB group plasma has no antibodies so can be given to any type
What are the basic compatibility guidelines for matching donor blood products for RBCs?
- Identical ABO
- if patient Rh negative, need Rh negative donor
- if Rh positive, can receive both
- if has antibodies such as anti-C, E, K, select donor RBCs without antigen
- cross match compatible
What are the basic compatibility guidelines for matching donor blood products for platelets?
- identical ABO
- if Rh- select Rh- donor….if unavailable, can give Rh+ with anti D if patient is female with child bearing potential
- if patient Rh+ can have Rh+ or Rh-
- crossmatched, HLA A or BU matched, HLA phenotype compatible, if patient has anti-HLA antibodies
- crossmatched platelets if patient has anti-HPA antibody
What are the basic compatibility guidelines for matching donor blood products for plasma?
- identical ABO
- any Rh type, Rh doesn’t matter when transfusing thawed plasma products
What are the basic compatibility guidelines for matching donor blood products for cryoprecipitate transfusion?
- ABO identical
- but there’s small plasma volume, so any donor ABO group is acceptable. Rh doesn’t matter
What are the most important antibodies affecting transfused leukocytes?
- Anti HNA
- Anti HLA
