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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
Selected cells are used too
rule out antibodies on panels that have several antibody possibilities
26
One you determine the antibodies on the antibody screen you must
type the patients cells for antigens (as long as they have not been recently transfused)
27
If a patient has multiple antibodies to high frequency antigens, you may need to
get blood from the American Rare Donor Program
28
Enhancement media is used to
strengthen the antibody-antigen reactions
29
What is the simplest form of enhancement>
increase the serum to cell ration | 3 drops serum to 1 drop of cells
30
What are the benefits and drawbacks of albumin as enhancement media?
Enhances Rh antibodies Brings in nuisance antibodies Requires 30 minute incubation Rarely Used
31
What are the benefits and drawbacks of PEG as enhancement media?
Enhance Kidd and Duffy antibodies | Brings in warm autoantibodies
32
Which antigens are destroyed by enzymes?
``` Duffy MaNuScript Duffy MNS(s) ```
33
What are the proteolytic enzymes?
Ficin Papain Trypsin Bromelin
34
What are the 2 sulfhydryl reagents and what is their purpose?
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
Ficin is used to
Remove Duffy MNS(s) antigens | Removes these antigens to find other "masked" antibodies present in backgrouns
36
DTT is used to
destroy Kell, LW, and Scianna antigens | Can be used as a selected cell
37
What kind of antibodies are insignificant. Examples
Some antibodies which are only cold reactive | Anti-Leb, Anti-P1, Anti-M, Anti-N, Anti-A1
38
Any antibody reacting at 37 degrees is
clinically significant
39
Antibodies not reactive at the AHG phase my be
clinially insignificant
40
This percent of hospital patients has a positive DAT
1-15% (much higher then the general population)
41
The DAT procedure refects the in ___ reactions of patients
in vivo (in the body)
42
What is the purpose of the DAT test
to check to see if red blood cells are coated with complement and /or antibodies in vivo (in the body)
43
DAT procedure
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
About 13% of poditive DAT tests are sue to
C3d
45
What is eveidence of decreased red cell survival?
``` Increased retics Elevated bilirubin Decreased Hct with no evidence of bleeding Positive DAT prescence is significant ```
46
A positive autocontrol my be a sign of
Delayed Hemolytic Transfusion Reaction | DAT is probably positive too
47
When a positive DAT is a mixed field it is because
The transfused cells are coated, but the patients cells are not
48
What is an elution test?
A test which strips antibodies from cells. An antibodie screen can be run on an eluate.
49
A Last Wash Control ensures
Antibodies came off of RBCs and were not from serum or plasma
50
What is a warm autoantibody?
Antibodies to antigens on a patients RBCs that react at body temperature
51
What is AIHI?
Autoimmune Hemolytic Anemia
52
This test will almost always be positive in patients with Autoimmune Hemolytic Anemia (AIHI)
DAT (90% of patients)
53
In 50-90% of patients with AIHI, this will be found in their serum
autoantibodies
54
_____ must be excluded by adsorption/elution procedures because they mask _______.
Alloantibodies must be excluded because they mask autoantibodies
55
When autoantibodies are adsorbed onto RBCs this must be used as enhancement
ZZAP
56
Low incidence atingens %
1%
57
High incidence antigen %
90%
58
Fy(a-b-) is nonexistant in this race, but exists in
Fy(a-b-) not in Caucasians | Present in African Americans
59
How do newborns get antibodies?
From mom throught the placenta
60
How do you test a baby for HDNF?
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
A patient can have passively aquired antibodies (such as anti-A and anti-B) if they were transfused
with non-ABO identical plasma

Blood Bank Test 3b (3 decks)

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