ABO Grouping and Discrepancies

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Questions and Answers

What is the purpose of forward grouping in ABO testing?

To check for blood compatibility

To detect antibodies in plasma

To determine the blood type from historical data

To identify antigens on red blood cells (correct)

What indicates a positive test result in ABO grouping?

Agglutination of the red blood cells (correct)

Absence of any reaction

Clear plasma sample

Presence of unusual colors in the plasma

Which testing method can reveal the presence of antibodies in the patient's plasma?

Antibody screening

Forward grouping

Cross-matching

Reverse grouping (correct)

What can missing or weak reactions in the forward group suggest?

A possible sub-group of A or B Signup and view all the answers

What does agglutination with an Anti-A,B reagent confirm?

That both A and B antigens are present Signup and view all the answers

In the context of discrepancies, which type of reactions is considered more reliable?

Stronger reactions Signup and view all the answers

How should the results of forward and reverse ABO grouping relate to each other?

They should correlate to confirm ABO typing Signup and view all the answers

What is an example of an ABO discrepancy?

Mixed field agglutination Signup and view all the answers

What is the result of having the cis-AB genotype?

Weak expression of ABO antigens Signup and view all the answers

What effect can excessive amounts of soluble A and/or B antigen in plasma have during testing?

It neutralizes the reagent antiserum Signup and view all the answers

Which of the following methods can enhance the detection of weak ABO antigens?

Enzyme treating the patient’s cells Signup and view all the answers

What commonly causes mixed-field agglutination in a blood sample?

Non-ABO identical RBC transfusions Signup and view all the answers

What is a transient cause of mixed-field agglutination observed in some patients?

Chimerism after bone marrow transplantation Signup and view all the answers

How does chimerism occur in fraternal twins?

By exchange of blood-forming cells in utero Signup and view all the answers

Which subgroup is an example of a weak ABO dominant antigen?

A3 subgroup Signup and view all the answers

What is likely to happen in emergency transfusions when testing on a current sample is incomplete?

Transfusion of group O red blood cells Signup and view all the answers

What is the purpose of proteolytic enzyme treatment in blood grouping?

To enhance weakly reactive ABO antibodies Signup and view all the answers

Which of the following is NOT a proteolytic enzyme used in enzyme treatment?

Chymotrypsin Signup and view all the answers

What causes rouleaux formation in red blood cells during testing?

Abnormally elevated globulin plasma protein Signup and view all the answers

What is polyagglutination associated with?

Exposure of hidden antigens on red blood cells Signup and view all the answers

What is the role of controls of group O and autologous cells when performing enzyme treatment?

To confirm ABO antibody reactivity Signup and view all the answers

Which of the following substances can cause nonspecific agglutination in ABO tests?

Hyaluronic acid in Wharton’s jelly Signup and view all the answers

What might be necessary to resolve discrepancies due to Wharton’s jelly contamination?

Washing cells multiple times with warm saline Signup and view all the answers

What are cryptantigens?

Hidden antigens on red blood cell membranes Signup and view all the answers

What should be done first when a discrepancy is discovered in testing results?

Repeat the testing to rule out technical errors Signup and view all the answers

Which of the following can indicate an issue with reagents used in testing?

Decreasing strength of reaction over time Signup and view all the answers

In the case of an ABO discrepancy, what might historical results indicate?

The specimen may have been mislabeled Signup and view all the answers

What does the presence of signs like cloudiness or color changes in reagents indicate?

The reagent may be contaminated Signup and view all the answers

What issue could similar ABO discrepancies on sequential samples suggest?

The centrifuge may be overdue for calibration Signup and view all the answers

What could lead to unexpected positive reactions in the reverse group?

Presence of non-ABO antibodies Signup and view all the answers

In a suspected group A or AB individual, a positive reaction with A1 cells could indicate what?

The individual is a subgroup of A2 with anti-A1 Signup and view all the answers

Which of the following is a condition that may produce unexpected ABO antibodies?

Cold autoagglutinins Signup and view all the answers

What is likely if there is a positive reaction with A1 cells and a negative reaction with O cells?

Likely anti-A1 Signup and view all the answers

Cis-AB individuals may exhibit which characteristic in their ABO tests?

Weak expression of A and/or B antigens Signup and view all the answers

What is the recommended method to confirm suspected anti-A1 antibodies?

Phenotyping the patient with Dolichious biflorus Signup and view all the answers

Which of the following antibodies commonly results in ABO discrepancy?

Anti-P1 Signup and view all the answers

What does a positive reaction with both A1 cells and O cells suggest?

Anti-A1 in combination with another antibody Signup and view all the answers

Study Notes

ABO Grouping

ABO testing includes two components: forward and reverse grouping
Forward grouping identifies antigens by combining unknown red blood cells with known antibody (anti-A or anti-B)
Reverse grouping identifies antibodies by combining unknown plasma with known ABO red blood cells (A1 or B)
Agglutination (positive test) indicates the presence of the corresponding antigen or antibody
No agglutination (negative test) indicates the absence of the corresponding antigen or antibody
ABO blood type is determined by antigens present on red blood cells and confirmed by the correlation of forward and reverse grouping
Anti-A,B reagent can agglutinate A, B, or AB cells, used to check forward reactions and identify subgroups

ABO Discrepancies

ABO discrepancies occur when forward and reverse reactions do not agree
Mixed field agglutination and inconsistent results between current and historical testing also indicate discrepancies
Weaker reactions are more likely to be aberrant than stronger ones

Missing or Weak Reactions in the Forward group

Subgroups of A or B: May exhibit weaker reactions
Cis-AB genotype: Both A and B genes on the same chromosome, resulting in weak antigen expression
Malignancies (Leukemia): May alter A or B antigens, leading to weak or missing reactions
Soluble A or B antigens in plasma: Can neutralize reagent antiserum, causing false-negative results. Using washed cells avoids this
Methods to enhance detection of weak ABO antigens:
- Modified testing procedures: extended incubation or enzyme treatment
- Saliva inhibition test (for secretors)
- Genetic analysis
Mixed field agglutination: The presence of two different cell populations, often caused by transfusion of non-ABO identical cells
- Transfusion of group O red blood cells in emergencies prevents intravascular hemolysis
- ABO nonidentical bone marrow or hematopoietic progenitor cell transplantation can also result in mixed-field agglutination
- Weak ABO subgroups like A3 can cause mixed-field agglutination
- Chimerism: two different cell populations reside together after transplantation
- Mosaicism: two sperm fertilize one egg, resulting in two distinct cell populations

Enzyme Treatment for Weak Antibodies in Reverse grouping

Use of enzymes like ficin, papain, bromelin, and trypsin can enhance weak ABO antibody reactivity
Control cells (group O and autologous) should be treated with enzymes for accurate interpretation

Unexpected Positive Reactions in the Forward group

Substances in plasma: Wharton's jelly, elevated globulin plasma protein, cold autoagglutinins, antibodies to antiserum constituents
Polyagglutination: Agglutination with all plasma due to exposed antigens on the red blood cell membrane (cryptantigens)

Unexpected Positive Reactions in the Reverse group

Acquired ABO antibodies: Due to IVIG, ABO-incompatible plasma or platelet transfusions
Non-ABO antibodies: Cold autoagglutinins, room temperature alloantibodies, antibodies to the reverse cells' suspension medium
Anti-A1: Can cause discrepancies in suspected group A or AB individuals
Subgroups of A or B or cis-AB: May produce unexpected ABO antibodies and weakened antigen expression
Distinguish anti-A1 from other cold antibodies:
- Confirming anti-A1 by phenotyping with Dolichous biflorus
- Rule out anti-A1 through phenotyping and testing against different A1 cells

Technical Errors

Repeat testing to identify procedural errors
Consult with your lab's procedures and reagent manufacturer's instructions
Check reagent controls for contamination or expiration
- Cloudiness, color change, or hemolysis indicate contamination
- Check expiration dates
Equipment problems: centrifuge calibration
Mislabeled specimens: drawing and testing a new sample to confirm

Additional Points

Examples provided for better understanding
The text emphasizes importance of accurate ABO testing for transfusion safety and patient management

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Description

This quiz covers the concepts of ABO grouping, focusing on forward and reverse grouping techniques, and the interpretation of agglutination tests. Additionally, it addresses ABO discrepancies that can occur during testing. Test your knowledge on the mechanisms and protocols used to determine blood types.