ABO Discrepancies

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ABO ABO DiscrepanciesDiscrepancies

Dr. MH Saiemaldahr Dr. MH Saiemaldahr

Blood BankBlood Bank

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ABO AntibodiesABO Antibodies

Generally Generally IgMIgM class antibodies class antibodies For Group A and Group B persons the For Group A and Group B persons the

predominantpredominant antibody class is antibody class is IgMIgM For Group For Group O O people the dominant antibody class people the dominant antibody class

is is IgG IgG (with some (with some IgMIgM)) React best at React best at room temperatureroom temperature (22-24 (22-24ooC) or C) or

below below in vitroin vitro.. Activates complement to completion at 37Activates complement to completion at 37ooCC CanCan cause acute cause acute Hemolytic TransfusionHemolytic Transfusion

reactionsreactions RBC Immune form: Predominantly RBC Immune form: Predominantly IgGIgG

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ABO AntibodiesABO Antibodies

Time of appearance:Time of appearance: Generally present within first Generally present within first 4-6 months4-6 months of life of life Reach adult level at Reach adult level at 5-10 years5-10 years of age of age Level off through adult lifeLevel off through adult life Begin to decrease in later years: Begin to decrease in later years: >65 years of >65 years of

ageage

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A and B SubgroupA and B Subgroup

They both react strongly with reagent They both react strongly with reagent anti-Aanti-A.. 80%80% of group of group AA individuals phenotype as individuals phenotype as A1A1 20%20% phenotype as phenotype as A2A2

Reagent Reagent anti-Aanti-A is a mixture of two Abs ; is a mixture of two Abs ;

anti-A which react with both A1 and A2 cells.anti-A which react with both A1 and A2 cells. anti-A1 which reacts with anti-A1 which reacts with A cellsA cells but not with but not with A2A2

cells in simple testing . cells in simple testing .

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QualitativeQualitative difference due to ; difference due to ;

1-8 % of A2 and 22-35 % of A2B individuals produce a readily identifiable anti-A1 in their serum.

QuantitativeQuantitative difference difference A2A2 cells carry 25 % as many cells carry 25 % as many AA antigen sitesantigen sites as do as do

A1A1 cells cells A1A1 individuals make individuals make AA antigen from all type II antigen from all type II

chains ( H1-4 ) .chains ( H1-4 ) . A2 individuals produce A antigen only from H1 and A2 individuals produce A antigen only from H1 and

H2 precursors.H2 precursors.

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Differentiation between the A blood Differentiation between the A blood subgroupssubgroups

Reagent anti-A is a mixture of two AbsReagent anti-A is a mixture of two Abs The two Abs can be functionally separated by The two Abs can be functionally separated by

adsorption adsorption with A2 cells.with A2 cells.

Anti-A1-lectinAnti-A1-lectin: is another source of : is another source of anti-A1anti-A1. . lectinslectins are are seed extractsseed extracts that agglutinate human that agglutinate human

cells with some degree of specificity. cells with some degree of specificity. The seeds of the plant The seeds of the plant Dolichos biflorusDolichos biflorus serve as serve as

the source of the anti-A1 lectin this reagent the source of the anti-A1 lectin this reagent agglutinate agglutinate A1 orA1 or A1BA1B cells but does not cells but does not agglutinate agglutinate A2 or A2BA2 or A2B cells. cells.

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Other A subgroups: RBC of the A Other A subgroups: RBC of the A intint, A, A33, Ax, A, Ax, Ay y or or A A clcl. are only rarely seen in transfusion practice.. are only rarely seen in transfusion practice.

Subgroup of B: infrequent than the weaker Subgroup of B: infrequent than the weaker subgroup of A, identified by anti-B and anti-A,B. subgroup of A, identified by anti-B and anti-A,B. Subgroups B3 , Bx , Bm and Bcl .Subgroups B3 , Bx , Bm and Bcl .

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ABO DiscrepanciesABO Discrepancies

ABO discrepancies happen when there is no ABO discrepancies happen when there is no match in results between forward and reverse match in results between forward and reverse grouping.grouping.

ABO discrepancies are usually ABO discrepancies are usually technicaltechnical in in nature and can be simply nature and can be simply resolved by correctly resolved by correctly reportingreporting the testing and carefully checking the testing and carefully checking reagents with meticulous reading and recording reagents with meticulous reading and recording of results.of results.

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There are some ABO discrepancies that can There are some ABO discrepancies that can happen due to technical errors and may lead to happen due to technical errors and may lead to false positive or false negative reactions.false positive or false negative reactions.

False positiveFalse positive reactions are due to; reactions are due to; Un-calibrated centrifugesUn-calibrated centrifuges Contaminated reagentsContaminated reagents Dirty tubes or glasswareDirty tubes or glassware

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False negativeFalse negative reactions can be due to many reactions can be due to many causescauses

Failure to add serum or reagentsFailure to add serum or reagents Use of incorrect reagents or samplesUse of incorrect reagents or samples Cell suspension is too heavy or too lightCell suspension is too heavy or too light Inadequate identification of samples or Inadequate identification of samples or

test tubestest tubes

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Group I discrepanciesGroup I discrepancies

These discrepancies are between These discrepancies are between forward and forward and reversereverse grouping due to weak reaction or grouping due to weak reaction or missing missing antibodiesantibodies..

These kind of discrepancies are the These kind of discrepancies are the most commonmost common..

The reason for the missing antibody or weak The reason for the missing antibody or weak reaction is that the patient has reaction is that the patient has depresseddepressed antibody antibody production or production or cannot producecannot produce the ABO antibodies. the ABO antibodies.

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This type of discrepancy can be seen in new This type of discrepancy can be seen in new born infants, elderly patients.born infants, elderly patients.

Patients with lymphoma.Patients with lymphoma.

Patients using immunosuppressive drugs.Patients using immunosuppressive drugs.

Patients with immunodeficiency disease, BM Patients with immunodeficiency disease, BM transplant.transplant.

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Resolving discrepanciesResolving discrepancies

Eliminate all Eliminate all technical errorstechnical errors Enhancing the reaction in Enhancing the reaction in reversereverse grouping grouping Incubate the patient’s serum with reagent cells Incubate the patient’s serum with reagent cells

at room temp. for 15 mins.at room temp. for 15 mins.

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Group II discrepanciesGroup II discrepancies

These discrepancies are between These discrepancies are between forward and forward and reversereverse grouping due to weak reaction or grouping due to weak reaction or missing missing antigensantigens..

This group is the This group is the least oneleast one. Can be caused by . Can be caused by some subgroups of some subgroups of A or subgroups of B or bothA or subgroups of B or both..

Also it can be present in patients with leukaemia Also it can be present in patients with leukaemia and hodgkin’s disease.and hodgkin’s disease.

To resolve the problem wash the patient’s cells To resolve the problem wash the patient’s cells with saline.with saline.

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Group III discrepanciesGroup III discrepancies

These discrepancies are between forward and These discrepancies are between forward and reverse grouping due to reverse grouping due to protein or plasma protein or plasma abnormalities.abnormalities.

These can be caused by These can be caused by elevated levels of elevated levels of globulinglobulin from certain diseases such as multiple from certain diseases such as multiple myloma, hodgekin’s lymphoma. Some are caused myloma, hodgekin’s lymphoma. Some are caused by (by (Rouleaux formation).Rouleaux formation).

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RouleauxRouleaux or red cells result from a stacking of or red cells result from a stacking of erythrocytes that adhere in a coin-link fashion erythrocytes that adhere in a coin-link fashion giving the appearance of agglutination.giving the appearance of agglutination.

To resolve this kind of problem, washing the To resolve this kind of problem, washing the patient’s red cells with saline or adding a drop or patient’s red cells with saline or adding a drop or two of saline to the tube in case of rouleaux two of saline to the tube in case of rouleaux formation.formation.

If the agglutination is true red cell clumping will If the agglutination is true red cell clumping will remain.remain.

Cord blood must be washed 6-8 times in forward Cord blood must be washed 6-8 times in forward grouping grouping ONLYONLY..

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Group IV discrepanciesGroup IV discrepancies These kind of discrepancies are between forward These kind of discrepancies are between forward

and reverse groping due to and reverse groping due to miscellaneousmiscellaneous problems.problems.

Polyagglutination can occur due to exposure of Polyagglutination can occur due to exposure of hidden erythrocyte Ag. (hidden erythrocyte Ag. (T antigen)T antigen) in patients in patients with bacterial or viral infection.with bacterial or viral infection.

Bacterial contamination in Bacterial contamination in vitrovitro or or vivo vivo produces produces an enzyme that alters and exposes the hidden an enzyme that alters and exposes the hidden Ag. on red cell leading to T activation.Ag. on red cell leading to T activation.

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Some examples of discrepanciesSome examples of discrepancies

Example 1Example 1 Forward grouping: anti-A =O, anti-B =O, anti-Forward grouping: anti-A =O, anti-B =O, anti-

AB= OAB= O Reverse grouping: A1 cells= O, B cells =OReverse grouping: A1 cells= O, B cells =O Blood group:Blood group: OO Possible discrepancy:Possible discrepancy: Missing Ab. Or group I discrepancyMissing Ab. Or group I discrepancy

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Example 2Example 2

Forward grouping: anti-A = 4+,anti-B =O, anti-Forward grouping: anti-A = 4+,anti-B =O, anti-AB =4+AB =4+

Reverse grouping: A1 cells =1+, B cells =4+Reverse grouping: A1 cells =1+, B cells =4+ Blood group:Blood group: AA Possible discrepancy:Possible discrepancy: Missing Ag. Or group II discrepancyMissing Ag. Or group II discrepancy

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Example 3Example 3

Forward grouping: anti-A 4+,anti-B 2+,anti-Forward grouping: anti-A 4+,anti-B 2+,anti-AB 4+AB 4+

Reverse grouping: A1 cells 4+, B cells 4+Reverse grouping: A1 cells 4+, B cells 4+ Blood group : ABlood group : A Possible discrepancyPossible discrepancy

Rouleaux formationRouleaux formation

ABO Discrepancies

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