Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Transfusion Medicine Fellowship > Pre-Transfusion Testing > Flashcards

Pre-Transfusion Testing Flashcards

1
Q

Blood component ABO requirements:

Whole blood, red blood cells

A

Whole blood should ideally be identical to recipient. It must be compatible with patient’s plasma.
Red blood cells must be compatible with patient’s plasma.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Blood component ABO requirements:

Granulocytes, plasma

A

Granulocytes must be compatibel with patient’s plasma.

Plasma must be compatible with patient’s red cells (trials of group A plasma in effect)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Blood component ABO requirements:

Platelets, cryoprecipitated antihemophilic factor

A

Platelets: ABO identical is better than red-cell compatible than none.
Cryo: All ABO groups are acceptable.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the difference between a type and hold, type and screen, and type and cross?

A

Type and hold: No antibody testing.
Type and screen: Standard, includes Ab screen.
Type and cross: Includes crossmatch that allocates units to patient.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are some causes of false-positive results in antiglobulin testing?

A 
Cells may be agglutinating before washing
Contaminants (dust/dirt/fibrin)
Improper procedures (overcentrifugation)
DAT+ cells
Complement (mostly C4)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are some causes of false-negative results in antiglobulin testing

A

Neutralization of AHG reagent
Interruption in testing (dissociation of IgG)
Improper reagent storage (AHG or cells)
Improper procedures (undercentrifugation)
Complement
Saline (pH, temperature)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What can cause incompatible IS crossmatch with a negative antibody screen?

A 
ABO incompatibility
Polyagglutination
Anti-A1 in an A2/A2B patient
Room-temperature alloantibodies (eg Anti-M)
Rouleaux
Cold autoantibodies
Passive anti-A or anti-B
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What can cause incompatible AHG crossmatch with a negative antibody screen?

A

DAT+
Variable antigen strength
Antibody to low-incidence antigen
Passive anti-A or anti-B

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why may a crossmatch be compatible even if an antibody screen is positive?

A

Donor lacks the relevant antigen
Anti-H or Anti-LebH (with non-O donor unit)
Dependence on reagent red cell diluent
Dosage/variable antigen strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How many samples are affected by WBIT errors?

A

1:2000

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Why may a pre-transfusion specimen be rejected?

A

Inability to confirm identity
Hemolyzed or lipemic sample
Wrong tube type (plasma, not serum)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What factors influence the Coombs reaction?

A

Temperature, Ig class, and most importantly specific Ab-Ag interactions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What percentage of alloantibodies fade in 1 yr? In 10 yrs?

A

1yr: 30%
10yrs: 50%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How safe is it to give O-positive units to men and older women?

A

Safe; significant hemolysis to Rh or other antigens on group O RBCs are very rare. Some hemolysis is probably permissible in this context anyway.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How can red cell alloantibodies be detected in the presence of a warm autoantibody?

A

Perform autologous adsorption to remove the autoantibody. If the patient was recently transfused, will have to use alloadsorption instead.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the effect of ABO-matching (or mismatching) platelets?

A

ABO-identical platelets reduce refractoriness but have no effect on mortality or bleeding events.

Major mismatched platelets are less effective (knocked out), minor mismatched may cause hemolysis (carrier anti-A/B).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the risk of Rh alloimmunization with platelets?

A

Low; platelets do not express Rh, but beware contaminating red cells. Can reduce risk by using apheresis platelets, giving to immunosuppressed patients, or using RhoGAM.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the most common cause of platelet refractoriness?

A

Non-immune causes, including DIC< active bleeding, splenism and drug effects.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How do platelets cause HLA immunization?

A

Platelets do express HLA class I antigens, but reaction is usually due to passenger leukocytes.

20
Q

Rabbit erythrocyte stroma (RESt)

A

Commercial reagent used to remove cold agglutinins (usually Anti-Ii/HI), but can also adsorb clinically significant antibodies as well.

21
Q

How can IgMs be subtracted from plasma?

A

Adsorption
Pre-warming
0.01M DTT

22
Q

ABO discrepancies: What are some causes for weak/missing red cell reactivity?

A 
ABO subgroups
Leukemia/malignancy
Transfusion
Pregnancy
Intrauterine fetal transfusion
Transplantation
Excessive soluble blood group substance
23
Q

ABO discrepancies: What are some causes for extra red cell reactivity?

A

Autoagglutinins/excess coating
Unwashed red cells (plasma proteins, reagent antibody)
Transplantation
Acquired B or other polyagglutinable conditions
cisAB or B(A) phenomenon
Out-of-group transfusion

24
Q

ABO discrepancies: What are some causes for mixed-field red cell reactivity?

A 
ABO subgroup
Recent transfusion
Transplantation
Fetomaternal hemorrhage
Chimerism
25
Q

ABO discrepancies: What are some causes for missing serum reactivity?

A 
Age-related
ABO subgroup
Hypogammaglobulinemia
Transplant
Excessive anti-A/B (prozone)
Hemodilution
26
Q

ABO discrepancies: What are some causes for extra serum reactivity?

A 
Cold agglutinins
Excess serum protein
Reagent antibody
Transfusion of plasma products
Transplantation
IVIG
27
Q

What antigens degrade over time on reagent cells?

A

Duffy antigens, M, P1, Kn(a), McC(a), Bg)

28
Q

In what setting is plasma NOT interchangeable with serum for pre-transfusion testing?

A

Any testing involving complement (eg. Anti-C3 DAT). You must use SERUM in this context.

29
Q

What should all reagent red cells be typed for?

A

D, C/c, E/e, K, Fya/b, Jka/b, MNS, P1, Le

30
Q

Give 3 examples of enhancement media?

A

LISS, PEG, 6-22% albumin

31
Q

What antigens are more strongly expressed on cord red cells?

A

i, LW(a), LW(b)

32
Q

When would a polyspecific AHG be preferred to a monospecific AHG?

A

To detect complement binding/activation, such as with JK antibodies.

33
Q

What medical conditions should be considered in interpreting antibody results?

A

Cold agglutinin disease, Reynaud, mycoplasma pnuemonia, PCH, SLE, CLL, MM, LPL/WM

34
Q

What is the difference between an autocontrol and DAT?

A

Autocontrols reflect in vitro conditions with contributions from reagents and artificial incubation settings.

35
Q

Why can’t PEG tests be read directly after centrifugation?

A

PEG will cause nonspecific aggregation, it must be washed out after incubation.

36
Q

What number of cells must be used to perform rule-ins?

A

Three positive reactive cells and three non-reactive negative cells.

37
Q

How do cold autoantibodies present on testing? How can they be subtracted?

A

Gels often look mixed field; correct by warming, using RESt, or cold adsorption.

38
Q

What antibodies to high-frequency antigens should be considered in white, black, and asian populations?

A

White: -k, -Kp(b)
Black: -U, -Js(b), -Hy, -Jo(a), -Cr(a)
Asian: -Di(b)

39
Q

How do rouleaux cause problems in testing? How are they managed?

A

Can cause ABO discrepancies and DAT false positives. Treated by washing (never a problem on IAT).

40
Q

What trick can you use to isolate sickle cells from donor transfused red cells?

A

Use hypotonic saline; sickle cells resist lysis.

41
Q

When obtaining cells for phenotyping, a positive DAT will preclude accurate phenotyping. What should you do to remove IgGs/IgMs?

A

Wash/elute off IgGs, use 0.01M DTT to remove coated IgMs (or, pre-warm)

42
Q

What antigens are enhanced by ficin/papain?

A

Rh, Kidd

ABO, I, P, Le

43
Q

Give some examples of antibody inhibitors

A

Mostly just soluble antigens, useful for subtracting antibodies or confirming identity. Lewis, P1, Sda, Ch/Rg

44
Q

What methods are usable for elution?

A

Heat/freeze-thaw only for ABO reactions.

Acid/solvent for all others.

45
Q

What significant antibodies may not be reactive on IAT/37C?

A
  • Vel
  • P
  • PP1Pk (-Tj(a))
  • H

Transfusion Medicine Fellowship (34 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions