ABO Blood Grouping and Immunohematology Study Guide Flashcards

Vocabulary flashcards covering key concepts, diagnostic procedures, ABO typing discrepancies, and compatibility rules in immunohematology.

Blood Group Immunoglobulin Classes

The primary immunoglobulin classes of most blood group antibodies are IgG and IgM.

Routine ABO Blood Bank Testing

Routine testing performed by blood bank technologists to determine the ABO group of a patient determines the phenotype.

Bombay Phenotype ($O_h$)

An individual with the Bombay phenotype is differentiated from a Group O individual because their plasma contains anti-H, and their RBCs react negatively with Ulex europaeus.

Acquired B Antigen Typing Pattern

Characterized by Anti-A $4+$, Anti-B $2+$, A1 cells $0$, and B cells $4+$. Associated with GI disease (such as colon cancer), gram-negative septicemia, and intestinal obstructions.

IgM Agglutination Capability

IgM antibodies directly agglutinate RBCs and cause visible reactions because they are pentamers capable of binding more antigen.

L-fucose

The essential sugar required on a precursor substance for A and B antigens to be expressed.

Subgroup $A_1$ vs. $A_2$ Differentiation

Differentiated using Dolichos biflorus lectin (RBCs of an $A_2$ individual give a negative reaction) and detecting anti-$A_1$ in the patient's plasma.

Secondary Antigenic Stimulation Antibody Class

IgG is the antibody class produced in the highest quantity following secondary antigenic stimulation.

Group O Secretor Antigens (SeSe)

A Group O individual with the SeSe genotype expresses only H antigens in both their saliva and plasma.

Complement in Intravascular Hemolysis

Required alongside antigen-antibody binding for intravascular hemolysis to occur.

Immunodeficiency ABO Typing Pattern

Results in missing plasma reactions (Anti-A $0$, Anti-B $4+$, A1 cells $0$, B cells $0$) due to low antibody production.

$A_2$ Subgroup with Anti-$A_1$ Reaction Profile

Expected testing results: Anti-A ($4+$), Anti-B ($0$), Anti-A,B ($3\text{-}4+$), Anti-$A_1$ lectin ($0$), A1 cells ($1\text{-}2+$), B cells ($3\text{-}4+$), A2 cells ($0$), O cells ($0$).

RBC Sensitization Factors in AHG Testing

Factors influencing sensitization include pH, incubation time, incubation temperature, ionic strength of the test environment, and zeta potential.

Lattice Formation Factors in AHG Testing

Factors influencing lattice formation include centrifugation speed and time, antigen/antibody concentration, number of binding sites, immunoglobulin size, zeta potential, and location/number of antigenic determinants.

Antigen-Antibody Binding Forces

Non-covalent forces affecting binding avidity and affinity include electrostatic forces, Van der Waal's forces, hydrogen bonds, size, and shape.

Causes of Mixed-Field Agglutination

Common causes in ABO typing include recent transfusion (two cell populations), $A_3$ subtype, and neonates with poorly developed antigens.

Serum Saline Replacement (SSR) Protocol

A 4-step procedure used to resolve rouleaux: 1. Re-spin discrepant backtype tubes, 2. Pipette off plasma, 3. Replace plasma with $2\text{-}3$ drops of saline, 4. Spin tubes containing saline and reverse cells (true agglutination remains).

$A_3$ Subgroup Characterization

An ABO subgroup defined by mixed-field reactivity when the patient's RBCs are tested with anti-A.

Tube Agglutination Grading ($2+$ vs. $4+$)

$2+$ reactivity displays many medium to small aggregates with a clear background; $4+$ reactivity displays mostly one large aggregate with a clear background.

In Vitro Hemolysis Interpretation

Hemolysis occurring actively in vitro during testing is interpreted as a POSITIVE reaction.

ABO Antibody Properties

Naturally occurring IgM antibodies that can activate complement and cause massive intravascular hemolysis.

ABO Blood Group Antigen & Product Compatibility Table

A reference table outlining antigens, antibodies, compatible RBC products, and compatible plasma products across groups O, A, B, and AB.

Bombay Phenotype Genotype

Arises strictly from the homozygous recessive genotype $hh$.

ABO Discrepancies and Resolutions Table

A reference table matching specific backtype and forward typing discrepancies to conditions like immunodeficiency, multiple myeloma, cold hemagglutinin disease, $A_2$ subgroup with anti-$A_1$, and acquired B.

Cold Hemagglutinin Disease ABO Discrepancy

Presents with extra reactions in typing (Anti-A $4+$, Anti-B $4+$, A1 cells $2+$, B cells $2+$); resolved using prewarm technique.

Multiple Myeloma ABO Discrepancy

Causes false positive reactions (rouleaux) due to elevated plasma protein; resolved using Serum Saline Replacement (SSR).

All-Negative ABO Typing Pattern Discrepancy

Forward typing: Anti-A $0$, Anti-B $0$; Reverse typing: A1 cells $0$, B cells $0$. Resolved by increasing plasma drops, incubating at room temperature for $15\text{ mins}$, or incubating at $4^\times\text{C}$ for $15\text{ mins}$.

Dolichos biflorus

A plant lectin used in blood bank testing to differentiate between $A_1$ and $A_2$ cells.

H Antigen Quantity Ranking

The relative concentration of H antigen present on red blood cells from most to least is $O > A_2 > B > A_2B > A_1 > A_1B$.