Coomb's Test and Compatibility Testing

Question 1

used primarily to detect globulins immunologically bound to red cells.

Answer 1

ANTIGLOBULIN TEST or COOMB’S TEST

Question 2

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

Answer 2

Polyspecific or multivalent or broad-spectrum reagent

Question 3

Polyspecific or multivalent or broad-spectrum reagent contains

Answer 3

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

Question 4

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

Answer 4

Polyspecific or multivalent or broad-spectrum reagent

Question 5

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

Answer 5

Monospecific or monovalent reagent

Question 6

can detect most clinically significant antibodies

Answer 6

Anti—lgG

Question 7

Monospecific reagent is useful in

Answer 7

differentiating agglutination produced by IgG antibodies

Question 8

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

Answer 8

C3d component

Question 9

Monospecific sera containing _____ or _____ are not routinely used

Answer 9

anti— IgM or anti—lgA

Question 10

used for the detection of in vivo red blood cell sensitization

Answer 10

DIRECT ANTIGLOBULIN TEST

Question 11

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

Answer 11

DIRECT ANTIGLOBULIN TEST

Question 12

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

Answer 12

Patients red cells to be tested

Question 13

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

Answer 13

INDIRECT ANTIGLOBULIN TEST

Question 14

antibody—containing serum is incubated with specified red blood cell

Answer 14

Indirect Antiglobulin Test

Question 15

______ is to be tested in indirect antiglobulin test

Answer 15

Patien’ts serum

Question 16

Method that uses ANTIGLOBULIN REAGENT and CENTRI 1 minute

Answer 16

DIRECT ANTIGLOBULIN TEST

Question 17

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

Answer 17

Indirect antiglobulin test

Question 18

Extreme reticulocytosis
Lead poisoning
Drug—induced hemolysis
Viral diseases

Results in: False ______

Answer 18

False positive DAT is seen in:

Question 19

Factors affecting the antiglobulin test in vitro:

Answer 19

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

Question 20

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

Answer 20

rapid and uninterrupted

Question 21

Factors affecting the antiglobulin test

Answer 21

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

Question 22

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

Answer 22

False negative

Question 23

Contamination with human serum will neutralize the reagent resulting in

Answer 23

False negative result

Question 24

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

result:

Answer 24

False negative

Question 25

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

Answer 25

False negative results

Question 26

Preferred percentage in cell suspension for Coomb's test

Answer 26

2% to 5% suspension of RBC

Question 27

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.

Answer 27

False negative result

Question 28

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

Answer 28

False negative result

Question 29

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

Answer 29

False negative

Question 30

Old serum will also have impaired complement activity resulting in

Answer 30

False negative

Question 31

Undercentrifugation or overcentrifugation causes

Answer 31

False negative reaction

Question 32

Failure to check negative reactions, microscopically

Answer 32

False negative reaction

Question 33

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

Answer 33

False positive results

Question 34

Bacterial contamination of test cells or septicemia causes

Answer 34

False positive

Question 35

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

Answer 35

False positive reaction

Question 36

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

Answer 36

False positive reaction

Question 37

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.

Answer 37

False positive reaction

Question 38

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.

Answer 38

False positive reaction

Question 39

Overcentrfugation

Answer 39

False positive reaction

Question 40

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

Answer 40

False positive reaction

Question 41

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

Answer 41

False positive

Question 42

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

Answer 42

crossmatch or compatibility test

Question 43

Purpose of cross matching

Answer 43

To prevent any possible transfusion reaction due to antibody. To ensure maximum benefit to the recipient.

Question 44

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.

Answer 44

Major

Question 45

uses patients red cells and donors serum (DS—PR). detects antibodies in the donor which may be capable of affecting the recipients' red cells

Answer 45

Minor

Question 46

crossmatch WILL DETECT the following

Answer 46

Most recipient antibodies directed against antigens on the donor red blood cells. Major errors in ABO grouping, labeling and identification of donors and recipients

Question 47

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

Answer 47

Crossmatch will not

Question 48

Specimen for crossmatch

Answer 48

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

Question 49

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.

Answer 49

Saline Technique

Question 50

The saline crossmatch at 37 deg C detects

Answer 50

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

Question 51

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

Answer 51

Bovine albumin

Question 52

albumin crossmatch at 37 deg C detects

Answer 52

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

Question 53

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

Answer 53

Antiglobulin technique

Question 54

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

Answer 54

Enzyme technique

Question 55

enzyme used in enzyme technique

Answer 55

Trypsin Papain Ficin Bromelin

Question 56

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

Answer 56

Broad spectrum Compatibility Testing

Question 57

Three phases of broad spectrum compatibility test

Answer 57

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

Question 58

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).

Answer 58

Roleaux formation

Question 59

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.

Answer 59

rouleaux

Question 60

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

Answer 60

Panagglutination

Question 61

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.

Answer 61

Bacteriogenic panagglutination / Huebner Thomsen—Friedenrich phenomenon

Question 62

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

Answer 62

Nonbacteriogenic panagglutjnation

Question 63

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.

Answer 63

Polyagglutination

Question 64

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

Answer 64

Cold grouping

Question 65

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

Answer 65

Wharton's jelly

Question 66

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).

Answer 66

Prozones

Question 67

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.

Answer 67

Antigen or antibody deterioration