Untitled Flashcards Set

### ABO Blood Grouping System

Blood grouping is based on the presence or absence of antigens on red blood cells and antibodies in plasma. These determine blood compatibility in transfusions.

#### Inheritance & Genetics

- Blood type is inherited from parents and controlled by the ABO gene on chromosome 9.

- The ABO gene has three possible alleles:

- A allele → Produces A antigen.

- B allele → Produces B antigen.

- O allele → Does NOT produce any ABO antigen.

- A & B alleles are dominant over O, meaning:

- AA or AO → Type A

- BB or BO → Type B

- AB → Type AB

- OO → Type O

#### Antigens & Possible Groups

- Antigens are carbohydrate molecules on RBC surfaces.

- Plasma contains naturally occurring antibodies against antigens not present in the individual.

- Blood types:

- Type A → A antigen, anti-B antibodies.

- Type B → B antigen, anti-A antibodies.

- Type AB → A & B antigens, no antibodies (Universal recipient).

- Type O → No ABO antigens, anti-A & anti-B antibodies (Universal donor).

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### H Antigen

- Acts as a precursor molecule for both A and B antigens.

- Found in everyone except individuals with Bombay phenotype (rare condition lacking H antigen).

- Bombay phenotype individuals cannot receive normal ABO blood due to the lack of H antigen.

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### Landsteiner’s Law

- Established by Karl Landsteiner, who discovered the ABO system in 1901.

- Law states:

1. An individual naturally produces antibodies against ABO antigens they do NOT have.

2. No person normally has antibodies against their own blood group antigens.

- Example:

- Type A person → Produces anti-B antibodies.

- Type B person → Produces anti-A antibodies.

- Type AB person → No ABO antibodies.

- Type O person → Produces both anti-A and anti-B antibodies.

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### IgM & IgG (Immunoglobulins)

These are types of antibodies in blood that play different roles.

#### IgM

- Large pentamer-shaped antibody.

- Found mainly in ABO blood group reactions.

- Causes immediate agglutination (clumping) of mismatched RBCs in a transfusion.

#### IgG

- Smaller monomer-shaped antibody.

- Important in Rh system reactions.

- Can cross the placenta, potentially causing Hemolytic Disease of the Fetus and Newborn (HDFN).

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### Significance of ABO Antibodies

- Mismatched transfusions can trigger hemolysis (destruction of RBCs) due to ABO antibodies.

- IgM antibodies act quickly and can cause severe transfusion reactions.

- ABO compatibility is critical for ensuring safe blood transfusions.

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### Rh System & D Antigen

- The Rh system involves several antigens, but the D antigen is most clinically significant.

- Rh-positive people have D antigen; Rh-negative people lack it.

- Rh incompatibility is important in pregnancy and transfusions.

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### Hemolytic Disease of the Fetus and Newborn (HDFN) & Anti-D Prophylaxis

- Occurs if an Rh-negative mother carries an Rh-positive fetus.

- Mother’s immune system produces anti-D antibodies after exposure to fetal blood.

- In later pregnancies, IgG antibodies cross placenta, attacking fetal RBCs.

- Prevention → Anti-D immunoglobulin injection is given to the mother to prevent antibody formation.

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### Other Blood Group Systems

Each blood group system influences transfusion compatibility and disease susceptibility.

- Kell System → Can cause severe hemolytic transfusion reactions & HDFN.

- Duffy System → Determines malaria resistance & affects transfusion reactions.

- Kidd System → Associated with delayed hemolytic reactions.

- MNS System → Plays a role in cell adhesion & transfusion compatibility.

- Lewis System → Antigens change over time & are influenced by secretor status.

- Lutheran System → Generally not clinically significant, but rare cases exist.

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### Why These Blood Group Systems Matter

- Some systems cause dangerous reactions in transfusions.

- Others influence disease resistance, such as Duffy's role in malaria.

- Essential for pregnancy management, organ transplantation, and blood donations.

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### Components of Blood & Their Roles

Each component has a unique function and use in transfusion medicine.

- Red Blood Cells (RBCs) → Carry oxygen; transfused in anemia.

- White Blood Cells (WBCs) → Defend against infections; sometimes transfused in immune deficiencies.

- Platelets → Clot blood; used for bleeding disorders.

- Plasma → Contains antibodies & clotting factors; useful in coagulation disorders.

- Cryoprecipitate → Rich in clotting proteins (fibrinogen); used for hemophilia.

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### Antibodies & Antigens in Blood Groups

- Antigens → Molecules on RBC surfaces that determine blood type (e.g., ABO, Rh).

- Antibodies → Proteins that attack foreign blood group antigens.

- Blood Group Antigens govern compatibility in:

- Transfusions

- Pregnancy

- Immune responses

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## Role of the Transfusion Laboratory

The transfusion laboratory is essential for ensuring safe blood transfusions. It plays a key role in:

- Determining blood compatibility before transfusion.

- Identifying antibodies that might cause transfusion reactions.

- Crossmatching blood to prevent hemolytic reactions.

- Managing blood components (RBCs, platelets, plasma) for various medical conditions.

- Investigating hemolysis and transfusion complications.

- Ensuring compliance with clinical guidelines for transfusion medicine.

Blood transfusion errors can be life-threatening, making the accuracy of testing crucial.

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## Pre-Transfusion Testing

Before a blood transfusion is given, several laboratory tests are performed to ensure safety:

### 1. Blood Group Determination

- Blood type is identified using ABO and Rh testing.

- Antigens on RBCs are detected using anti-A, anti-B, and anti-D reagents.

### 2. Antibody Screening

- Detects unexpected antibodies in the patient's plasma.

- Important for identifying antibodies like anti-D, anti-K, and others that could cause hemolysis.

- Uses Indirect Antiglobulin Test (IAT) and various RBC panel cells to detect reactions.

### 3. Crossmatching

- Confirms that donor blood is compatible with the patient.

- Immediate Spin Crossmatch detects ABO incompatibility.

- IAT Crossmatch detects antibodies requiring AHG for reaction.

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## Reagents & Their Sources

Reagents are chemical or biological substances used in transfusion testing.

### Common Reagents in Blood Testing

- Monoclonal antibodies: Highly specific lab-made antibodies.

- Polyclonal antibodies: Sourced from human or animal sera.

- Anti-human globulin (AHG): Used in Indirect Antiglobulin Tests (IAT).

- Enzymes (e.g., papain, ficin): Modify RBC antigens for antibody detection.

- Buffer solutions: Maintain correct conditions for testing.

### Sources of Reagents

- Commercial laboratories produce standardized reagents for blood testing.

- Some reagents come from donated human serum containing specific antibodies.

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## Controls in Testing

Quality control ensures accuracy and reliability in blood testing.

### Key Quality Checks

1. Incubation control → Ensures correct antigen-antibody interaction.

2. Centrifugation checks → Confirms proper separation and reaction visibility.

3. Temperature monitoring → Some tests require 37°C incubation.

4. Equipment calibration → Ensures centrifuges, incubators, and analyzers function properly.

5. Protocol adherence → Follows strict standard operating procedures (**SOPs**).

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## Agglutination Methods

Agglutination testing detects antigen-antibody reactions by observing clumping of red blood cells.

### Types of Agglutination

1. Direct Agglutination

- RBCs naturally clump when exposed to specific antibodies.

- Example: ABO blood group testing.

2. Indirect Agglutination

- Uses anti-human globulin (AHG) to enhance weak antigen-antibody reactions.

- Example: Rh antibody detection.

3. Column Agglutination Technology

- Uses gel columns to visualize reactions clearly.

- Provides more sensitivity in antibody detection.

4. Liquid Phase & Solid Phase Testing

- Liquid phase → Traditional method using test tubes.

- Solid phase → Uses microplate systems for enhanced detection of antibodies.

5. IAT Using AHG Cards (Indirect Antiglobulin Test)

- Detects clinically significant antibodies.

- Used for crossmatching, antibody screening, and hemolysis investigations.

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## Interpreting Positive & Negative Reactions

- Positive reaction → Indicates incompatibility or presence of antibodies.

- Negative reaction → Suggests compatibility and no detectable antibodies.

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## ABO, Rh, and Antibody Screening

- ABO & Rh typing → Confirms major blood group compatibility.

- Antibody screen → Detects clinically significant antibodies before transfusion.

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## Antibody Identification

Once an antibody is detected, further testing identifies its specificity.

### Methods of Identification

- Cellstab panels → Uses commercial RBCs with known antigen profiles.

- Enzyme-treated RBCs → Enhances expression of certain antigens to identify specific antibodies.

- EDTA-treated samples → Removes complement activity to avoid false-positive reactions.

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## Handling Unidentified Antibodies

When an antibody cannot be identified, further testing methods are used:

- Adsorption studies → Removes interfering antibodies.

- Elution techniques → Extracts antibodies from RBCs for analysis.

- Advanced molecular testing → Confirms rare antibody types.

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## Crossmatching

Crossmatching ensures patient plasma is compatible with donor blood.

### Methods

1. Immediate Spin Crossmatch

- Quick check for ABO compatibility.

- Used when no antibodies are detected.

2. IAT Crossmatch (Indirect Antiglobulin Test)

- Detects antibodies that require AHG for reaction.

- Necessary for patients with a history of transfusions or pregnancy.

3. Electronic Crossmatching

- Automated system using validated software.

- Used when patients have no detectable antibodies.

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## NHS Blood and Transplant (NHSBT)

- Manages blood donation, testing, and supply in the UK.

- Provides rare blood units for complex cases.

- Supports transplant and transfusion services.

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## What Happens If Transfusion Goes Wrong?

A mismatched transfusion can cause life-threatening reactions.

### Severe Reactions

1. Hemolytic Transfusion Reaction (HTR)

- Rapid destruction of RBCs due to ABO incompatibility.

- Symptoms: fever, hypotension, hemoglobinuria, kidney failure.

2. Delayed Hemolytic Reaction

- Occurs days after transfusion due to minor antibodies.

- Symptoms: low hemoglobin, jaundice, mild fever.

3. Febrile Non-Hemolytic Reaction (FNHTR)

- Caused by white cell antibodies or cytokines.

- Symptoms: fever & chills (not life-threatening).

4. Allergic Reactions

- Triggered by plasma proteins in donor blood.

- Mild cases cause rashes; severe cases can lead to anaphylaxis.

5. Iron Overload

- Occurs in patients needing repeated transfusions.

- Excess iron damages organs, requiring chelation therapy.

### Prevention Measures

- Strict compatibility testing before transfusion.

- Review of previous transfusion history.

- Immediate medical intervention if reaction occurs.

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## Final Thoughts

Transfusion science is critical for patient safety. Understanding:

- Pre-transfusion testing

- Agglutination techniques

- Antibody identification

- Crossmatching methods

Ensures safe and effective blood transfusions.

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