Question 1

Most clinically significant blood group antibodies are of which IgG subclasses?

Accepted Answer

B

Question 2

What is the incubation time for the IAT when saline is used instead of LISS?

Accepted Answer

The incubation time for the Indirect Antiglobulin Test (IAT) when saline is used instead of Low Ionic Strength Solution (LISS) is 30 minutes.

Question 3

What effect does a low pH have on a saline AHG test?

Accepted Answer

A low pH (acidic conditions) enhances antibody elution, making it easier for antibodies to dissociate from red blood cells and bind to the antiglobulin reagent. This can result in a false-positive test or weaker reactivity than expected. Additionally, lower pH levels can also increase bacterial growth, leading to increased contamination.

Question 4

Why was anticomplement introduced into AHG sera?

Accepted Answer

Anticomplement is introduced into AHG sera because certain clinically significant antibodies demonstrate complement activity, complement components can enhance the action of some antibodies such as those in the Kell system, and it provides additional information for transfusion reaction workups, making all the given options correct.

Question 5

How is a 40:1 ratio of serum to cells prepared for the AHG test?

Accepted Answer

A 40:1 serum to cell ratio means there are 40 parts serum to 1 part cells. To prepare this ratio, we need to add 2 parts serum to 1 part cells. Therefore, option C which is 2 drops of serum and 1 drop of a 5% v/v RBC suspension is the correct answer.

Question 6

What do "check cells" contain?

Accepted Answer

The answer of What do "check cells" contain?
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Question 7

The indirect antiglobulin test detects which antigen-antibody reactions?

Accepted Answer

The indirect antiglobulin test is performed in vitro to detect antibodies against red blood cells that are not naturally bound to the cells. This test is used, for example, in blood typing and crossmatching before transfusions.

Question 8

The antihuman globulin (AHG) test was discovered in 1945 by whom?

Accepted Answer

The antihuman globulin (AHG) test, also known as the Coombs test, was discovered by Robin Coombs in 1945. Landsteiner discovered the ABO blood groups and won the Nobel Prize for his work in 1930. Mollison contributed to the study of blood groups and transfusions, but did not discover the AHG test. Sanger won the Nobel Prize for his work in determining the structure of DNA.

Question 9

At what temperature is the incubation phase of the AHG test?

Accepted Answer

The incubation phase of the AHG test is typically performed at 37°C. This temperature is optimal for the binding of antibodies to complement and red blood cells, which allows for detection of antigen-antibody reactions. Choice A (22°C) is too low and would likely result in incomplete or delayed reactions. Choice C (4°C) is too cold and would not allow for proper binding of antibodies and complement. Choice D (56°C) is too high and would likely cause denaturation of the antibodies and complement, rendering the test ineffective.

Question 10

What is the action of PEG?

Accepted Answer

PEG (Polyethylene Glycol) acts by removing water molecules, which results in the concentration of antibodies. This process enhances the agglutination reaction in serological testing by bringing the antigens and antibodies closer together.

Question 11

If not labeled "gamma heavy chain-specific," monospecific anti-IgG may contain antibodies to:

Accepted Answer

Monospecific anti-IgG antibodies will bind to IgG molecules, but if they are not labeled as "gamma heavy chain-specific," they may also bind to the light chains of other immunoglobulin isotypes (such as IgM or IgA) that contain the same light chains as IgG. Therefore, choice A is the best answer. Choices B and C are incorrect because they refer to heavy chains of different isotypes, and monospecific anti-IgG antibodies should not bind to them. Choice D is also incorrect because it refers to a complement protein, not an immunoglobulin molecule.

Question 12

Why is incubation omitted in the direct AHG test?

Accepted Answer

In the direct AHG test, in vivo antigen antibody complexes are already formed, so there is no need for incubation to promote agglutination.

Question 13

"Complete" agglutinins that agglutinate red blood cells in saline are of which immunoglobulin class?

Accepted Answer

IgM antibodies are the largest immunoglobulin and exist as pentamers held together by disulfide bonds. They are the first antibodies to be produced in response to a new antigen and are highly effective at agglutinating microbes or foreign blood cells. In saline solution, complete IgM agglutinins can agglutinate red blood cells, making them useful in blood typing and cross-matching.

Question 14

A patient came in for a routine type and screen prior to surgery. The antibody screen was negative at 37°C and at the AHG phase. Check cells did not produce agglutination often. What is a possible explanation for this result?

Accepted Answer

Inadequate washing can lead to the presence of residual plasma components or other substances that interfere with the test system and can lead to false negative results.

Question 15

Which of the following is consistent with hemolytic disease of the newborn (HDN)?

Accepted Answer

HDN occurs when maternal antibodies, typically anti-RhD, cross the placenta and attack fetal red blood cells that possess the RhD antigen. This results in hemolysis of the fetal red blood cells and can lead to severe anemia and other complications in the newborn.

Question 16

In preparing anti-IgG, how is excess antibody removed for titer adjustment?

Accepted Answer

The answer of In preparing anti-IgG, how is excess antibody...

Question 17

All of the following are important in evaluating a positive DAT except:

Accepted Answer

Donation history is not relevant in evaluating a positive Direct Antiglobulin Test (DAT), which is used to determine if there are antibodies attached to the red blood cells. The patient's diagnosis, drug therapy, and transfusion history are all relevant factors that can influence the result of a DAT.

Question 18

Polyspecific AHG contains:

Accepted Answer

Polyspecific AHG contains both anti-IgG and anti-C3d antibodies, allowing detection of both complement and antibody-mediated reactions.

Question 19

An advantage of polyclonal anti-IgG over monoclonal anti-IgG is:

Accepted Answer

Polyclonal anti-IgG will recognize multiple epitopes on the IgG molecule, including variants, which increases its versatility compared to monoclonal anti-IgG that typically recognize only one epitope.

Question 20

What is a possible consequence of incubating tubes too long with LISS when performing the IAT?

Accepted Answer

The answer of What is a possible consequence of incubating...

Quiz 5: The Antiglobulin Test