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IMH laboratory > Coomb's Test and Compatibility Testing > Flashcards

Coomb's Test and Compatibility Testing Flashcards

1
Q

used primarily to detect globulins immunologically bound to red cells.

A

ANTIGLOBULIN TEST or COOMB’S TEST

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2
Q

basic type of reagent used in routine blood banking procedures, such as compatibility testing and antibody screening

A

Polyspecific or multivalent or broad-spectrum reagent

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3
Q

Polyspecific or multivalent or broad-spectrum reagent contains

A

anti—lgG and anti—C3d (anti-complement component)

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4
Q

________ reagent may contain antibodies of other specificities, such as anti—lgM, anti—lgA anti—c3b or anti—C4

A

Polyspecific or multivalent or broad-spectrum reagent

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5
Q

Example of this is the anti—lgG and the anticomplement C3b + C3d (previously called anti—non—gamma)

A

Monospecific or monovalent reagent

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6
Q

can detect most clinically significant antibodies

A

Anti—lgG

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7
Q

Monospecific reagent is useful in

A

differentiating agglutination produced by IgG antibodies

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8
Q

It isassociated with immune hemolysis; therefore, it is important that this component be included in anti—complement reagents to facilitate investigation of immune hemolytic anemias

A

C3d component

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9
Q

Monospecific sera containing _____ or _____ are not routinely used

A

anti— IgM or anti—lgA

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10
Q

used for the detection of in vivo red blood cell sensitization

A

DIRECT ANTIGLOBULIN TEST

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11
Q

Washed red blood cells from the patient are directly tested with antiglobulin serum

A

DIRECT ANTIGLOBULIN TEST

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12
Q

2 drops of _________ are to be tested in direct antiglobulin test

A

Patients red cells to be tested

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13
Q

used for the detection of antibodies that may cause red blood cell sensitization in vitro-

A

INDIRECT ANTIGLOBULIN TEST

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14
Q

antibody—containing serum is incubated with specified red blood cell

A

Indirect Antiglobulin Test

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15
Q

______ is to be tested in indirect antiglobulin test

A

Patien’ts serum

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16
Q

Method that uses ANTIGLOBULIN REAGENT and CENTRI 1 minute

A

DIRECT ANTIGLOBULIN TEST

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17
Q

This test uses 2 drops of cell suspension, incubation in water bath for 37 deg C for 15-30 mins

A

Indirect antiglobulin test

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18
Q

Extreme reticulocytosis
Lead poisoning
Drug—induced hemolysis
Viral diseases

Results in: False ______

A

False positive DAT is seen in:

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19
Q

Factors affecting the antiglobulin test in vitro:

A

Sensitization:
a)Temperature
b)Medium (saline, albumin, serum or enzyme)
c)Time of incubation
d)Proportion of serum to cells

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20
Q

Washing phase in antiglobulin should be ———– to minimize loss of cell bound antibody by elution

A

rapid and uninterrupted

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21
Q

Factors affecting the antiglobulin test

A
  1. Sensitization phase (in vitro only)
    a)Temperature
    b)Medium (saline, albumin, serum or enzyme)
    c)Time of incubation
    d)Proportion of serum to cells
  2. Washing phase — it should be rapid and uninterrupted to minimize loss of cell-bound antibody by elution
  3. Effects of centrifugation
  4. Methods of reading result
  5. Controls used
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22
Q

Inadequate washing of red cells result in neutralization of the antiglobulin serum by trace amounts of residual globulin will result ______

A

False negative

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23
Q

Contamination with human serum will neutralize the reagent resulting in

A

False negative result

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24
Q

Elution of antibody from the red cells may take place if the test is interrupted or delayed, particularly during the washing phase

result:

A

False negative

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25
Q

The optimum temperature for reactivity of the antibody must be maintained during incubation to achieve maximal coating of the cells resulting in _______

A

False negative results

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26
Q

Preferred percentage in cell suspension for Coomb’s test

A

2% to 5% suspension of RBC

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27
Q

A cell suspension that is too heavy will not permit optimum coating with the antibody; if too weak, reading agglutination may be difficult. A 2% to 5% suspension of RBC is preferred.

A

False negative result

28
Q

Test cells, test serum and antiglobulin serum lose reactivity if improperly stored resulting in

A

False negative result

29
Q

Some antibodies may be detected only in the presence of active complement Anticoagulants such as EDTA will chelate calcium, preventing activation of complement Thus, the use of plasma rather than serum may lead to a ________ reaction

A

False negative

30
Q

Old serum will also have impaired complement activity resulting in

A

False negative

31
Q

Undercentrifugation or overcentrifugation causes

A

False negative reaction

32
Q

Failure to check negative reactions, microscopically

A

False negative reaction

33
Q

Cells have a positive direct antiglobulin test cannot be used with reagent antiserum that require an antiglobulin phase, because all such cells have agglutinated the antiglobulin serum

A

False positive results

34
Q

Bacterial contamination of test cells or septicemia causes

A

False positive

35
Q

Extreme reticulocytosis because of transfusion bound to reticulocytes reacting with antitransferrin in the globulin reagent

A

False positive reaction

36
Q

Saline stored in glass bottle may contain colloidal silica leached from the container

A

False positive reaction

37
Q

Saline stored in metal containers or used in equipment with metal parts, may contain metallic ions which may bring about nonspecific protein—coating of the red cells.

A

False positive reaction

38
Q

Improperly prepared antiglobulin serum may contain traces of species specific antibodies.

When all the antiglobulin tests are weakly positive, the cause may be improperly cleaned glasswares or other forms of contamination.

A

False positive reaction

39
Q

Overcentrfugation

A

False positive reaction

40
Q

Patients or donor’s serum contain a naturally occurring cold autoantibody that can sensitize their own or other complement

A

False positive reaction

41
Q

Red blood cells may be autoagglutinated before they are washed, and this agglutination may persist through veshing leading to a ______ reaction when antiglobulin serum is added

A

False positive

42
Q

test between a patient or recipient of a blood transfusion and his prospective or donors.

A

crossmatch or compatibility test

43
Q

Purpose of cross matching

A

To prevent any possible transfusion reaction due to antibody.

To ensure maximum benefit to the recipient.

44
Q

crossmatch that uses patient’s serum and donor’s red cells (PS—DR)

prevent a transfusion reaction by detecting antibodies in the patient’s serum which would reduce the survival of the donors cells and to ensure maximum benefit to the recipient.

A

Major

45
Q

uses patients red cells and donors serum (DS—PR).

detects antibodies in the donor which may be capable of affecting the recipients’ red cells

A

Minor

46
Q

crossmatch WILL DETECT the following

A

Most recipient antibodies directed against antigens on the donor red blood cells.

Major errors in ABO grouping, labeling and identification of donors and recipients

47
Q

1.Guarantee normal donor cell survival
2.Prevent recipient immunization
3.Detect errors of Rh and ABO typing
4.Detect all antibodies unless antibody is specific to the donor antigen being crossmatched
5.Detect antibodies to white blood cells or platelets
Detect errors of labeling and collection of sample

A

Crossmatch will not

48
Q

Specimen for crossmatch

A

Fresh, not inactivated serum, less than 48 hours old must be used for the crossmatch

Hemolyzed patient samples should be avoided, because they may ask for hemolysis of donor red blood cells

washed red blood cell suspension may be prepared

49
Q

are designed to detect IgM antibodies react optimally at room temperature (22 deg C) or lower.

Agglutination or hemolysis in this procedure at 22 deg C will detect

ABO incompatibility, often due to incorrect typing.
Cold agglutinin or autoagglutinins.
acting antibodies such as anti—M, anti—N, anti—S, anti—Lu, anti—F and anti— Le.

A

Saline Technique

50
Q

The saline crossmatch at 37 deg C detects

A

Saline acting anti—Rh antibodies.
Some anti—M, anti—N and anti—S antibodies.
Some anti—K and anti—Le antibodies

51
Q

act to increase the dielectric constant of the medium, thus allowing IgG antibodies to be demonstrated, Most IgG antibodies are detected

A

Bovine albumin

52
Q

albumin crossmatch at 37 deg C detects

A

a.Most anti—Rh antibodies
b.Some anti—M, anti—N and anti—S antibodies
c.Some anti—Le antibodies

53
Q

most important and most widely used serologic procedure in modem blood banking. Compatibility testing should be considered incomplete unless the technique is included as part of the test

A

Antiglobulin technique

54
Q

serve as an irnportant “back up” test for the indirect antiglobulin test and detect many clinically significant IgG and saline—inactive IgM antibodies

A

Enzyme technique

55
Q

enzyme used in enzyme technique

A

Trypsin
Papain
Ficin
Bromelin

56
Q

developed to be an all-inclusive test, one which would detect clinically significant antibodies without sacrificing speed — so essential in an emergency, or simplicity so important in prevailing errors

A

Broad spectrum Compatibility Testing

57
Q

Three phases of broad spectrum compatibility test

A

a.Protein or room phase
b.Thermo or incubation period
c.Antiglobulin phase

58
Q

Cells appear to be agglutinated, yet they have the appearance of a “stocks of coins’ The formation can be dispersed or diminished by the addition of a drop of saline to the slide (diluting the serum-cell mixture with saline).

A

Roleaux formation

59
Q

often encountered in certain disease states — notably myelomatosis and macroglobulinemia. It is also caused by a raised serum giobulin concentration and is often seen in patients with serum protein abnormalities. Certain synthetic plasma expanders, such as dextran can also cause —— formation.

A

rouleaux

60
Q

simply the spontaneous clumping of all cells against a given serum. There are two main types of this reaction

A

Panagglutination

61
Q

due to a bacterial contaminant, which exposes a latent receptor known as T. All human red cells contain this antigenic receptor but are usually non—reactive with ant—T. Since all human adult sera contain anti—T in varying amounts, agglutination would occur with all such cells.

A

Bacteriogenic panagglutination / Huebner Thomsen—Friedenrich phenomenon

62
Q

may be used by acquired hemolytic anemia or by rare specific antibodies. The reaction takes place at 37 deg C and occasionally in the cold. The direct antiglobulin test is often positive

A

Nonbacteriogenic panagglutjnation

63
Q

reaction of red cells with varying proportions of fresh normal allogeneic or intert AB sera. The reaction takes place at 20deg C and becomes weak or inactive at 37 deg C.

A

Polyagglutination

64
Q

are relatively common problems in the laboratory, They are simple antibodies reacting at temperatures between 4 deg C and 20 deg C and they may be specific or nonspecific

A

Cold grouping

65
Q

Usually present in cord samples that have been collected by cutting the umbilical cord and allowing the blood to drain into a collection tube

A

Wharton’s jelly

66
Q

phenomenon occasionally occurs in the antiglobulin technique and is thought to be caused by partial neutralization of the antiglobulin reagent (i — the antibody is loosely bound or does not remain on the cells).

A

Prozones

67
Q

undergo a diminishing of reactivity on storage. The deterioration of antibodies is dependent on the specificity of the antibody and the length and method Of storage.

A

Antigen or antibody deterioration

IMH laboratory (1 decks)

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