Transfusion Medicine & Antibody Titration

Immunohematology

The study of immunologic responses to blood components

Blood Banking

Procedures involved in collecting, storing, and processing blood. The distribution of RBC and blood components

Transfusion Medicine

Medical practices and clinical uses associated with procurement (acquiring), processing, and distribution of blood components to patient

Benefits & Reasons for Transfusion

1. Restore/maintain hemoglobin. Done by transfusion of RBC w/o plasma from packed RBC

2. Restore/maintain blood volume. Whole blood transfusion is limited to situations involving massive trauma

3. Replace coagulation factors to maintain hemostasis. Components include platelet and cryoprecipitate

4. Restore/maintain leukocytes. Granulocytopenic (reduced granulocytes) patients with infections that do not respond to antibiotic

Component

Products prepared from whole blood by mechanical methods such as centrifugation

Blood Derivative/Fractions

Products separated by more complex automated processes

Packed Red Blood Cells

• If the container is entered (opened), the RBC are usable within 24 hours.

• Packed RBC replaced whole blood transfusion practice. Even in the case of severe blood loss, combined RBC and plasma substitutes are used

• Blood are irradiated to prevent proliferate of T-lymphocytes that cause GVHD

• Used to restore oxygen-carrying capacity

• Have the same expiration date if kept sterile while being prepared as the original donor unit

Graft-Versus-Host Disease

The donor T-lymphocytes detect recipient’s body as foreign and attack the tissues

Fresh Frozen Plasma

• Replace heat-labile coagulation factors

• Not used to replace blood volume or proteins because it can transmit disease. Safer methods including albumin, salt solution (prepared by chemical fractionation of pooled plasma), synthetic colloids (saline/electrolytes).

• Good for treating immune deficiencies

• NOT a source of all coagulation factor

Factor VIII

• Clotting proteins in blood that play intristic pathway of coagulation cascade

• Traditionally produce from fresh frozen plasma. Transition to using monoclonal antibody technology to reduce risk of transmitting diseases

Cryoprecipitate

• Extracted from fresh frozen plasma

• Used as replacement for fibrinogen in cases of liver failure, massive transfusion, or deficiencies in fibrinogen

Plateletpheresis

• High yield collection of platelets from whole blood (all components except platelets are returned to donor)

• Random donor platelets: four to six random donors (compatible ABO type) units are pooled into a single bag for transfusion. Expire 4 hours after pooling

• Platelet concentrates must be monitored for bacterial contamination, are useful in case of massive blood loos & replacement. It can stimulate production of HLA antibodies

Donor Guideline

• 17 years old (16 by state law)

• Weight > 110 pounds

• Not have donated whole blood in the last 8 weeks or double red cells in the last 16 weeks

• Medical screening

• Measure temperature, pulse, BP, hematocrit

• 1 unit of blood (450mL) is collected

• Additional 30mL in extra tubes for testing (HIV, HBV, HCV, HTLV, Syphilis, T-Cell Lymphotropic virus, West Nile virus, T-cruzi)

Anticoagulants & Preservatives

• Contain citrate to bind calcium

• Contain dextrose to provide energy source for RBC

• Phosphate buffer to increase ATP production (RBC viability)

• Adenine to prolong shelf life up to 35 days

• Store at 1C to 6C. Some type of alarm go off if the temperature deviates.

Autologous Transfusion

• Blood collected from patient for re-transfusion at later time into the same individual

• Intraoperative autologous transfusion (reinfuses own blood during operation)

Directed Transfusion

Blood transfusion from family or friends

Antigen

A marker that the immune system can detect as self or foreign and initiate appropriate actions

Alloantibodies

• Antibodies that was not present at first but form specifically against antigens from another individual

• Usually form after exposure through blood transfusion, pregnancy, organ transplant

• Example: Rh neg person develops anti-D after exposure to Rh pos

Blood Type Inheritance

Blood Type	Possible Genotype
A	AA or AO
B	BB or BO
AB	AB
O	OO

• If both parents are type OO, the kid can only be O

• If both parents are type AB, the kid cannot be O

• Phenotype of genotype AO is A

• Phenotype of genotype BO is B

Phenotype

What is seen by tests made directly on the RBC

Genotype

Total genetic makeup, impossible to determine the complete genotype in the laboratory. It requires additional studies especially family studies

Isoantibodies

• Naturally occurring ABO antibodies in the blood group system

• Type IgM

Immune Antobodies

• Antibodies that develop after the immune system is exposed to a foreign antigen

• Form after transfusion, pregnancy, transplantation

• Type IgG

Avidity

Strength of reaction with corresponding RBC antigens

Hemolysis

• Destruction of RBC by the antibody. Rupture of cell membrane and release of hemoglobin

• Result is a clear, cherry-red solution with no cloudiness because no cells are present

Complement

• Naturally present in the body, complex substance with 18 plasma protein components that aid in hemolysis

• Almost all antisera contains complement

Solid-Phase RBC Adherence Methods

• Step 1: Antigen is stuck to the well.

• Step 2: Patient antibody is added. It will wash away if not matched, binds to antigen if compatible.

• Step 3: Add indicator RBCs. It will bind to the antibody (if present) already on the well.

  • If antibodies were present → indicator RBCs stick to the well → forms a layer of cells all over the bottom.

  • If no antibodies were present → indicator RBCs do not stick → they form a tight button at the bottom when the plate is tilted.

Direct Antiglobulin Test (Front) vs Indirect Antiglobulin (Back)

• Front type: use known antibody with undetermined RBC

• Back type: use known RBC with unknown antibodies

Landsteiner’s Rule

• Corresponding antigens & antibodies cannot normally coexist in the same person RBC

• Ex: a person with A antigens cannot have antibody-A

Compatibility Testing

• Detect unexpected antibodies in the patient’s serum

• ABO compatibility

• Detect errors in labelling, recording, or identifying patients or donors

Crossmatching

Donor’s RBC with the patient’s serum to detect any antibody in the patient’s serum

Hemolytic Disease of Fetus Newborn (HDFN)

• The fetus has the antigen which the mother is negative.

• The D-antigen is the most severe/immunogenic (likeliness of stimulating immune response)

• The mother formed antibody IgG type that can cross the placenta into the fetus.

• The hemoglobin breakdown accumulates bilirubin. The infant can’t produce enzyme to convert bilirubin just yet and this causes severe neurologic problems

• Greatest exposure of the mother to the baby’s RBCs with D antigens is during labor and delivery. That’s why it does not occur in the first pregnancy

• ABO HDFN occurs when the mother is of type O and the baby is NOT type O

RhIG/RhoGAM

• Injected in intramuscularly within 72 hours of delivery in mothers

• The anti-d (Rh immune globulin) in the injection bind to fetal antigen-D to prevent the mother from developing anti-D

Antibody Titration

• Method to measure titrate (concentration) of maternal antibodies against fetal blood cell antigens. Monitor HDFN using serial twofold dilution

• Serial dilute of maternal serum and test against red cells containing the antigen

• Record the highest titrate (highest dilution factor that have agglutination)

• A fourfold change in titer is

  considered significant

• Periodically test to measure the trend of titer. Or if ti

  • Stable titer → low risk to fetus

  • Rising titer → increased antibody production

  • Significant rise → possible fetal hemolysis

  • Critical titer: titer is 16 or 32, considered at risk for HDFN

Maternal Immunizing Event

Exposure of mother to foreign RBC antigens that triggers antibody production

1. Amniocentesis: medical procedures in prenatal diagnosis of genetic conditions

2. Miscarriage

3. Abortion

4. Chorionic villus sampling: sampling of placental tissue

5. Cordocentesis: fetal blood sampling

6. Blunt trauma to the abdomen

7. Rupture of an ectopic pregnancy: fetal tissue & blood enter maternal circulation

3 Classification of HDFN

• ABO

• Rh

• Other

Prenatal Serologic Tests

• ABO/D type & antibody screen

• Antibody identification

• Determine clinical significance based on patient history/previously affected infant

Human Leukocyte Antigens (HLA)

• Found on WBC and most tissues

• HLA antibodies produced when exposed to foreign HLA through

  • Blood transfusion

  • Organ/tissue transplant

  • Pregnancy