Blood Banking Coombs Tests Overview

Questions and Answers

Who first described the Coombs test?

Dr. Albert Coombs

Dr. Futoon Al-Rawashde

Dr. James Watson

Dr. Robin Coombs (correct)

What does the Direct Antiglobulin Test (DAT) detect?

Presence of hemoglobin in plasma

In vitro sensitization of RBC

Scavenging of free antibodies in serum

In vivo sensitization of RBC with IgG or complement (correct)

What role do Coombs Control Cells (CCC) serve in antiglobulin testing?

They provide a quality control measure for antiglobulin tests. (correct)

They act as a neutralizing agent for unbound globulins.

They increase the concentration of AHG reagents.

They facilitate the washing of red cells.

Which molecule does the Antiglobulin Test (AHG) primarily react with?

Human antibodies Signup and view all the answers

What can cause a false-negative result in the antiglobulin test?

Presence of free globulins Signup and view all the answers

What is required for antibody detection in antiglobulin tests?

Coombs Control Cells Signup and view all the answers

How can IgG-sensitized cells affect antiglobulin tests?

They demonstrate that AHG was added and functional. Signup and view all the answers

What is the significance of removing unbound proteins before adding AHG serum?

To prevent neutralization of AHG and false-negative results. Signup and view all the answers

What does a positive DAT result indicate?

Agglutination is observed after centrifugation. Signup and view all the answers

Which condition is NOT investigated using the DAT test?

Symptomatic anemia Signup and view all the answers

What is the main purpose of the Indirect Antiglobulin Test (IAT)?

To detect in-vitro reactions between red cells and antibodies. Signup and view all the answers

What should be done first in the DAT procedure?

Wash the patient's RBCs 3 times. Signup and view all the answers

Which antibody type is primarily associated with hemolytic disease of fetus and newborn (HDFN)?

Alloantibody Signup and view all the answers

Which option describes an indirect effect of transfusion on DAT?

Alloantibodies in a recipient's circulation reacting with transfused antigens. Signup and view all the answers

What condition is linked to drug-induced hemolysis?

Autoantibodies against certain drugs binding to RBC membranes. Signup and view all the answers

What happens to the RBCs if no agglutination is observed in the DAT?

They will exhibit a negative DAT result. Signup and view all the answers

What does the Indirect Coombs Test (IAT) primarily detect?

Antibodies that have coated the red cells Signup and view all the answers

What is the first step in the indirect Coombs procedure?

Mix patient's serum with target RBCs Signup and view all the answers

What does agglutination indicate in the Indirect Coombs Test?

A positive test result Signup and view all the answers

What should be done if no agglutination occurs after the saline phase?

Add LISS and incubate for 15 minutes Signup and view all the answers

What action is performed after adding AHG in the final step?

Spin and observe for agglutination Signup and view all the answers

What does a negative result mean in the Indirect Coombs Test?

No agglutination, but CCC agglutinated Signup and view all the answers

Under what circumstance is a negative result considered invalid?

If CCC are not agglutinated after addition Signup and view all the answers

During the saline phase of the indirect Coombs test, what is the centrifuge speed?

3000 rpm Signup and view all the answers

Study Notes

Coombs (Antiglobulin) Tests Overview

Developed by Robin Coombs in 1945.
Consists of two main tests: Direct Coomb’s Test (DAT) and Indirect Coomb’s Test (IAT).

Principles of the Antiglobulin Test

Antibody molecules are globulins; animals produce antibodies against injected human globulins.
Adsorbed animal serum reacts specifically with human globulins, termed AHG serum.
AHG interacts with bound human antibodies and complement on red blood cells, enhancing antigen-antibody reactions.
Unbound globulins can neutralize AHG, potentially causing false-negative results.

Coombs Control Cells (CCC)

CCCs, or IgG-coated cells, serve as a quality control measure in antiglobulin tests.
Reactivity with CCC confirms that AHG was added and functional.
Lack of reactivity indicates the need to repeat the test due to potential neutralization of AHG.

Direct Antiglobulin Test (DAT)

Detects in vivo sensitization of red blood cells by IgG or complement antibodies.
Involves washing patient’s red cells, mixing with AHG, then centrifuging to observe agglutination.
Report results as:
- Positive: Agglutination observed.
- Negative: No agglutination observed.

Indications for DAT

Used for diagnosing:
- Hemolytic disease of the fetus and newborn (HDFN) due to alloantibodies.
- Hemolytic transfusion reactions.
- Autoimmune Hemolytic Anemia (AIHA) caused by autoantibodies.
- Drug-induced hemolysis related to autoantibodies.

Indirect Antiglobulin Test (IAT) / Group-Screen and Hold (GSH)

Identifies in-vitro reactions between red cells and antibodies that sensitize.
Agglutination after AHG addition confirms binding to specific red cell antigens.
Applications include antibody detection, identification, crossmatching, and weak D identification.

Indirect Coombs Procedure

Consists of several phases:
- Saline phase (Immediate Spin, IS).
- Incubation phase (37°C).
- AHG phase.
Involves mixing patient serum with screening cells, incubating, and observing for agglutination.

Interpretation of Antiglobulin Tests

IAT results:
- Positive test indicated by agglutination after incubation or upon AHG addition.
- Negative results seen when no agglutination is noted, and CCCs are agglutinated.
- If CCCs are not agglutinated, the negative result is invalid and requires re-testing.

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Description

Explore the fundamental concepts of Coombs tests including Direct Antiglobulin Test (DAT) and Indirect Antiglobulin Test (IAT). This quiz delves into the principles behind these essential procedures in blood banking and transfusion science as first described by Robin Coombs in 1945.