Transfusion Medicine Flashcards

1
Q

What does it mean when you get a type and screen?

A
  • type: ABO blood, Rh type

- screen: IAT-indirect antiglobulin test for antibodies patient has against any blood group antigen

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2
Q

What is a crossmatch?

A
  • done on donor blood before transfusion

- serum or plasma from patient’s blood tested with donor’s RBCs for agglutination or hymolysis

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3
Q

What does a direct anti globulin test (DAT) test for?

A
  • detects IgG and/or complement that coats RBCs in vivo
  • autoantibodies against own RBCs
  • ordered to see if patient’s anemia is immune mediated
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4
Q

What does an indirect anti globulin test (IAT) test for?

A

-red cell antibodies that are unbound to red cells

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5
Q

What determines ABO blood type?

A

-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.

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6
Q

What is fetal maternal ABO incompatibility?

A

-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.

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7
Q

What determines rhesus antigens and what are the different types?

A
  • 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
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8
Q

How can Rh hemolytic disease of the newborn occur?

A
  • 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
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9
Q

What are the different types of platelet antigens?

A
  • 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
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10
Q

Antibodies against which platelet antigens are commonly responsible for a number of diseases including autoimmune thrombocytopenic pupura?

A

platelet glycoproteins

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11
Q

What are the different types of human neutrophil alloantigens?

A

HNA system:

most important is HNA-3a

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12
Q

What is the difference between expected and unexpected alloantibodies? Which are the commonly expected and unexpected alloantibodies?

A

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

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13
Q

What are the characteristics of ABO blood group alloantibodies? expected? unexpected? naturally occurring? Describe which blood groups can receive which ABO blood transfusions.

A

-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

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14
Q

What are the characteristics of Rh alloantibodies? expected? unexpected? naturally occurring? Describe which blood groups can receive which Rh blood transfusions.

A

unexpected, blood exposure stimulated

-do not bind complement, extravascular hemolysis

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15
Q

What are other important RBC antibodies besides ABO and Rh?

A
  • Kidd system: anti-Jka, anti-Jkb
  • Kell system: anti-K
  • Duffy system: anti-Fya, anti-Fyb
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16
Q

Describe platelet antibodies and alloantibodies.

A
  • 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
17
Q

What are important antibodies to consider when transfusing plasma?

A

-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

18
Q

What are the basic compatibility guidelines for matching donor blood products for RBCs?

A
  • 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
19
Q

What are the basic compatibility guidelines for matching donor blood products for platelets?

A
  • 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
20
Q

What are the basic compatibility guidelines for matching donor blood products for plasma?

A
  • identical ABO

- any Rh type, Rh doesn’t matter when transfusing thawed plasma products

21
Q

What are the basic compatibility guidelines for matching donor blood products for cryoprecipitate transfusion?

A
  • ABO identical

- but there’s small plasma volume, so any donor ABO group is acceptable. Rh doesn’t matter

22
Q

What are the most important antibodies affecting transfused leukocytes?

A
  • Anti HNA

- Anti HLA