Immunohematology Blood Tests Quiz

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Questions and Answers

What is the primary purpose of the direct Coombs test?

To measure the level of red blood cells in plasma

To detect antibodies against foreign red blood cells

To diagnose autoimmune hemolytic anemia (correct)

To identify blood types prior to transfusions

What does a positive result in the direct Coombs test indicate?

Diminished hemoglobin levels in blood

Agglutination of foreign red blood cells

Presence of antibodies on red blood cell surfaces (correct)

Increased bilirubin production in the liver

What is detected by the indirect Coombs test?

Complement proteins in blood serum

Antibodies that are bound to the red blood cell surface

Antibodies floating freely in the blood (correct)

Red blood cell antigens in the plasma

In which scenario is the indirect Coombs test commonly performed?

In prenatal testing of pregnant women Signup and view all the answers

What step follows the incubation of serum with foreign red blood cells during the indirect Coombs test?

Addition of anti-human globulin Signup and view all the answers

What is the main consequence of antibodies detected by the direct Coombs test?

They can lead to the destruction of red blood cells. Signup and view all the answers

What kind of antibodies do the Coombs tests primarily detect?

IgG and IgM Signup and view all the answers

How are the anti-human antibodies used in the Coombs tests obtained?

By immunizing non-human animals with human plasma Signup and view all the answers

What does a positive Coombs test indicate regarding red blood cells?

An immune mechanism is attacking them. Signup and view all the answers

In which situation is the indirect Coombs test primarily used?

To prepare blood for transfusion. Signup and view all the answers

What is the main purpose of the direct Coombs test?

To detect antibodies on the surface of RBCs. Signup and view all the answers

Which of the following conditions can a positive Coombs test suggest?

Autoimmune hemolytic anemia. Signup and view all the answers

What role does the antihuman globulin reagent play in the direct Coombs test?

It agglutinates RBCs if bound antibodies are present. Signup and view all the answers

How are the results of the Coombs test typically assessed?

By the physician who requested the test. Signup and view all the answers

Which statement accurately describes the indirect Coombs test?

It screens for antibodies in a patient's serum. Signup and view all the answers

What is the primary clinical use of the direct Coombs test in infants?

To assess the risk of Rh disease. Signup and view all the answers

Which of the following is a common application of the Coombs test during antenatal care?

Identifying atypical antibodies in pregnant women. Signup and view all the answers

What is typically done to the patient’s RBCs before performing the direct Coombs test?

They are washed to remove serum. Signup and view all the answers

Study Notes

Coombs Tests Overview

Direct and indirect Coombs tests, or antiglobulin tests (AGT), are essential blood tests in immunohematology.
Direct Coombs test identifies antibodies attached to the surface of red blood cells (RBCs), essential for diagnosing autoimmune hemolytic anemia.
Indirect Coombs test detects free-floating antibodies in blood, indicating potential adverse reactions to blood transfusions.

Direct Coombs Test (DAT)

Used specifically to identify autoimmune hemolytic anemia, where the immune system damages RBCs leading to anemia.
Involves washing a blood sample's RBCs to remove plasma and unbound antibodies, followed by incubation with anti-human globulin.
Agglutination of RBCs indicates a positive test, signifying antibodies or complement proteins are bound to RBC surfaces.
Common clinical applications include blood transfusion preparation and detection of hemolytic disease in newborns.

Indirect Coombs Test (IAT)

Primarily employed in prenatal testing and compatibility testing before blood transfusions.
Serum is extracted from a blood sample and incubated with known antigenic foreign RBCs.
A positive reaction occurs when agglutination is observed after adding anti-human globulin, indicating the presence of antibodies against foreign RBCs.
Used for compatibility testing, antibody identification, and screening in antenatal care to prevent hemolytic disease of the newborn.

Mechanism of Coombs Tests

Both tests rely on anti-human antibodies binding to human IgG or IgM antibodies.
These anti-human antibodies are derived from non-human animals immunized with human plasma.
The binding leads to agglutination of RBCs under appropriate conditions, used as an indicator of a positive test result.

Clinical Significance

Positive Coombs tests indicate immune mechanisms (autoimmunity, alloimmunity, or drug-induced) are potentially attacking RBCs.
Coombs tests facilitate cross-matching during transfusions and assess atypical antibodies in pregnant women.
Conducted on samples from venipuncture, results are analyzed by trained laboratory staff and evaluated by physicians.

Key Terms

Agglutination: Clumping of RBCs indicating a positive reaction in Coombs tests.
Hemolytic Disease of the Newborn: Condition potentially screened using Coombs tests; caused by maternal antibodies attacking fetal RBCs.
Anti-human Globulin (Coombs Reagent): Key reagent in Coombs tests used to detect bound antibodies on RBC surfaces.

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Description

Test your knowledge on the direct and indirect Coombs tests, essential blood tests in immunohematology. Learn about the applications of these tests in detecting antibodies and clarifying anemia. This quiz will help reinforce your understanding of their roles and implications in blood banking.