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Blood Bank Test 3b > Chapter 6 > Flashcards

Chapter 6 Flashcards

1
Q

Hemagglutination ocurrs in 2 ways

A

Sensitization

Hemolysis

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2
Q

What is sensitization?

A

When antibodies attch to the antigens on RBCs and visibly agglutinates

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3
Q

What causes hemolysis?

A

Complement activation which results in the breakdown of the cell membrane

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4
Q

The antiglobulin test depends on 2 basic principles

A

Antibodies are globulins
The antihuman antibodies bind to the Fc portion of the sensitizing antibodies and form bridges between antibody-coated red cells, resulting in visible agglutination

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5
Q

The indirect antiglobulin test (IAT) was first used to

A

detect IgG anti-D

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6
Q

What factors affect the Indirect Antiglobulin Test?

A 
Incubation time and temperature
pH (6.8-7.2)
Ionic concentration (LISS)
Affinity constant of antibody
Proportion of antigen to antibody
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7
Q

What are the application of the indirect antiglobulin test?

A 
Unexpected antibody detection
Unexpected antibody identification
Antibody tiration
Red cell eluate testing
Cross match
Cell typing
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8
Q

The FDA requires screening be performed with group O cells with the following antigens

A

D, C, c, E, e, K, k, M, N, S, s, P1

Jka, Jkb, Fya, Fyb, Lea, Leb

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9
Q

Compatibility testing encompasses

A

ABO/Rh
Antibody Screen
Crossmatch

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10
Q

The antibody screen is used to

A

detect antibodies in the patient that are directed toward common or high prevelance antigens (will not detect low frequency antigens)

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11
Q

Autocontrol is

A

Mixing the paitents RBCs with the patients plasma to detect antibodies bound to the patients own RBCs

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12
Q

What are some issue that would cause a positive crossmatch but a negative antibody screen?

A

Incorrect ABO selected for crossmatch
Donor cells are subgroup of A or B ( which was incorrectly labeled as O)
Passive transfusion of ABO antibodies (A patient recieves O platelets)
Crossmatch contained low incidence antigens
Screening cells are single dose, crossmatch cells are double dose
Age of screen cells vs. fresh donor units

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13
Q

What percent of labs use gel technology?

A

45%

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14
Q

Why do most labs not perform IS or room temperature incubation?

A

To avoid cold reacting antibodies

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15
Q

Transfusion history is critical pre-analytical information. Between autoadsorption and alloadsorption, which one must be used for recently transfused patients?

A

Alloadsorption must be used for recently transfused patients.

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16
Q

What is an autoantibody?

A

An antibody produced by the immune system that is directed against one or more of the individuals own proteins.

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17
Q

What is an alloantibody?

A

An antibody formed in response to pregnancy or transfusion targeted against an antigen that is NOT present on the person’s RBCs (targeted against non-self red cell antigens)

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18
Q

To identify an antibody you must perfrom

A

DAT
Rh Phenotype (If Rh antibody suspected)
Initial Panel
Any follow-up selected cells

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19
Q

Antibody screening panel cells are always from this group

A

Group O

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20
Q

What is Direct Agglutination?

A

IgM

Binding to more than one red cell antigen at a time, bridging the cells together to form a clump

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21
Q

What is Indirect Agglutination

A

IgG
Sensitized RBCs are coated with antibody, but they can’t bridge the gap between cells. Add AHG reagent to detect coating of cells. (Coombs 1945)

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22
Q

A mix field specimen will conatin

A

2 cell populations (patients cells and donor’s transfused cells)

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23
Q

The sample used for pretransfusion testing must be under _____ old

A

3 days old

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24
Q

Many antibody panels will be positive for these high incidence antigens

A

Jsb, Kpb, Jra, Lub, Ata

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25
Q

Selected cells are used too

A

rule out antibodies on panels that have several antibody possibilities

26
Q

One you determine the antibodies on the antibody screen you must

A

type the patients cells for antigens (as long as they have not been recently transfused)

27
Q

If a patient has multiple antibodies to high frequency antigens, you may need to

A

get blood from the American Rare Donor Program

28
Q

Enhancement media is used to

A

strengthen the antibody-antigen reactions

29
Q

What is the simplest form of enhancement>

A

increase the serum to cell ration

3 drops serum to 1 drop of cells

30
Q

What are the benefits and drawbacks of albumin as enhancement media?

A

Enhances Rh antibodies
Brings in nuisance antibodies
Requires 30 minute incubation
Rarely Used

31
Q

What are the benefits and drawbacks of PEG as enhancement media?

A

Enhance Kidd and Duffy antibodies

Brings in warm autoantibodies

32
Q

Which antigens are destroyed by enzymes?

A 
Duffy MaNuScript
Duffy MNS(s)
33
Q

What are the proteolytic enzymes?

A

Ficin
Papain
Trypsin
Bromelin

34
Q

What are the 2 sulfhydryl reagents and what is their purpose?

A

STT and 2-ME
Cleaves disulfide bonds on IgM, making it unable to bind to antigens (used to rule out IgM)
Also affects k, Kpb, Jsb, LW, Yta

35
Q

Ficin is used to

A

Remove Duffy MNS(s) antigens

Removes these antigens to find other “masked” antibodies present in backgrouns

36
Q

DTT is used to

A

destroy Kell, LW, and Scianna antigens

Can be used as a selected cell

37
Q

What kind of antibodies are insignificant. Examples

A

Some antibodies which are only cold reactive

Anti-Leb, Anti-P1, Anti-M, Anti-N, Anti-A1

38
Q

Any antibody reacting at 37 degrees is

A

clinically significant

39
Q

Antibodies not reactive at the AHG phase my be

A

clinially insignificant

40
Q

This percent of hospital patients has a positive DAT

A

1-15% (much higher then the general population)

41
Q

The DAT procedure refects the in ___ reactions of patients

A

in vivo (in the body)

42
Q

What is the purpose of the DAT test

A

to check to see if red blood cells are coated with complement and /or antibodies in vivo (in the body)

43
Q

DAT procedure

A

Take a sample of RBCs, wash them to get rid of unbound antibody and complement, add AHG, centrifuge, look for agglutination.
Positive may mean: delayed HTR, autoantibodies, HDNF

44
Q

About 13% of poditive DAT tests are sue to

A

C3d

45
Q

What is eveidence of decreased red cell survival?

A 
Increased retics
Elevated bilirubin
Decreased Hct
with no evidence of bleeding
Positive DAT prescence is significant
46
Q

A positive autocontrol my be a sign of

A

Delayed Hemolytic Transfusion Reaction

DAT is probably positive too

47
Q

When a positive DAT is a mixed field it is because

A

The transfused cells are coated, but the patients cells are not

48
Q

What is an elution test?

A

A test which strips antibodies from cells. An antibodie screen can be run on an eluate.

49
Q

A Last Wash Control ensures

A

Antibodies came off of RBCs and were not from serum or plasma

50
Q

What is a warm autoantibody?

A

Antibodies to antigens on a patients RBCs that react at body temperature

51
Q

What is AIHI?

A

Autoimmune Hemolytic Anemia

52
Q

This test will almost always be positive in patients with Autoimmune Hemolytic Anemia (AIHI)

A

DAT (90% of patients)

53
Q

In 50-90% of patients with AIHI, this will be found in their serum

A

autoantibodies

54
Q

_____ must be excluded by adsorption/elution procedures because they mask _______.

A

Alloantibodies must be excluded because they mask autoantibodies

55
Q

When autoantibodies are adsorbed onto RBCs this must be used as enhancement

A

ZZAP

56
Q

Low incidence atingens %

A

1%

57
Q

High incidence antigen %

A

90%

58
Q

Fy(a-b-) is nonexistant in this race, but exists in

A

Fy(a-b-) not in Caucasians

Present in African Americans

59
Q

How do newborns get antibodies?

A

From mom throught the placenta

60
Q

How do you test a baby for HDNF?

A

Test for anti-ABO, Anti-D, or other antibodies
Run an eluate of positive DAT cells to determine what is coating baby’s cells
If it is an alloantibody, you can detect it in serum or plasma

61
Q

A patient can have passively aquired antibodies (such as anti-A and anti-B) if they were transfused

A

with non-ABO identical plasma

Blood Bank Test 3b (3 decks)

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