Deck B Flashcards
Enzymes are protiens that
that increase the rate of a chemical reaction
What are the most commonly used enzymes
ficin and papain.
- Less commonly used enzymes are
enzymes are bromelin, pronase, trypsin, and chemotrypsin.
Some red cell antigens are _________ by enzymes and others are ___________ by enzymes
Destroyed and enhanced
- Enzyme-treated red blood cells are typically used in two instances:
If a weakly reactive antibody is present, enzyme-treated red blood cells may be tested in an effort to enhance the reactivity and possibly clarify the reaction pattern or confirm the presence of the antibody.
Use of enzyme-treated red blood cells can often help differentiate antibodies.
- Enzyme treatment can be performed in two ways:
- The one-step technique: Enzyme is added as an enhancement to the tube containing test plasma and red blood cells and carried through the IAT phase of testing.
- The two-step technique: Requires treatment of the red blood cells with enzyme and washing prior to the addition of patient plasma. This method is often preferred because the enzymes in the one-step technique are added directly to the patient’s plasma and any antibodies present may be damaged.
- ________ red blood cells must be used in tandem with the ____________ red blood cells to identify all antibodies present in a test sample.
Untreated and enzyme-treated
Neutralization definition
The inactivation of an antibody by combining it with a soluble form of the corresponding antigen.
Neutralization can aid in
- Inactivation of the antibody can aid in identification of a suspected antibody that does not react with an ideal pattern.
Neutralization
Sources of
- Sources of neutralizing substances include saliva, hydatid cyst fluid, urine, plasma, breast milk, and amniotic fluid.
Elution
Frees antibody that is bound to a red blood cell.
Uses of an elution
Identify one or more antibodies attached to the red blood cell membrane.
Prepare antisera or to detect and identify weakly reactive antibodies.
Prepare DAT-negative red blood cells for further testing.
It can be combined with adsorption techniques to remove specific antibodies or antibodies.
Adsorption and elution techniques can be used to detect a weakly reactive antigen, such as a weak ABO subgroup.
- Methods that are best at releasing cold-reactive antibodies or antibodies that have a broad temperature range of reactivity include:
Lansteiner and Miller heat elution
Weiner’s freeze–thaw method
Lui’s freeze–thaw method and sonication
- Methods better suited for recovering warm-reactive alloantibodies or auto antibodies include
include use of organic solvents such as ether, zylene, methylene chloride, and chloroform or acids such as digitonin, citric, or glycine.
- Procedures that remove antibody but leave the red blood cells intact include
gentle heat, choloroquine, and acid glycine-EDTA methods.
- Preparation of a successful eluate can be influenced by several factors:
Improper technique
Inadequate stroma removal
Insufficient washing of the sensitized red blood cells before eluting the antibody
Incorrect method of transferring washed red blood cells
Incorrect procedure used during the wash phase
Use of saline to prepare eluates
Adsorption
- A technique used to remove an antibody or antibodies from plasma.
- Done most often to remove autoantibodies from a patient’s specimen in order to see if other antibodies are present in the plasma.
- Autologous adsorption and allogenic adsorption are the most common types used.
Adsorption
Is used to remove a antibody or antibodies from plasma
Done to remove autoantibodies to see if other antibodies are present In the patient plasma
- Autologous adsorption
cannot be used in the previous three months because the patient already has another type of red cell in his system
The preferred method to remove autoantibodies.
Cannot be used if the patient has been transfused within the previous 3 months because the patient’s specimen will also contain donor red blood cells.
- Allogenic adsorption
May be used when a patient with a autoantibody has been
Transfused
- Allogenic adsorption
Used either alone or paired with elution techniques to separate mixtures of
antibodies to allow for identification
When choosing red blood cells for adsorption, the red cells that stimulate the most ___________ antibodies are considered.
Clinically significant
Procedure requires a great deal of technical expertise because donor red blood cells adsorb both
autoantibodies and alloantibodies.
Allogenic adsorptions run the risk of not detecting a
clinical significant antibody if a weakly reactive alloantibody is diluted or antibody to a high-frequency antigen is absorbed. Autoantibodies that are only partially absorbed may mimic the reaction pattern of alloantibodies.
- Rabbit erythrocyte stroma
Can be used to adsorb certain
Removes what antibodies
Plasma absorbed by this method should not be used for
Can be used to adsorb certain antibodies.
Removes cold autoantibodies and anti-B and antibodies in the P blood group system (anti-P1).
Plasma adsorbed by this method should not be used for ABO typing.
- Rabbit erythrocyte stroma
Decreases the strength of or complexity removes other ___ from plasma including _________ significant antibodies
Decreases the strength of or complexly removes other IgM antibodies from plasma, including clinical significant antibodies.
Remains the adsorption medium of choice when an autoadsorption cannot be performed because a patient with a cold autoantibody has been recently transfused.
Available in commercial kits.
Titration
A technique used to measure the _______ of an antibody
Strength ( concentration)
Serial dilution
- Serial dilutions are made of the antibody containing plasma and tested against selected red blood cells to determine the highest dilution causing a positive reaction. The result or titer is expressed as the reciprocal of the highest plasma dilution reacting 1+.
Titer scores
- Titers can be resulted as a score, where a number is assigned to each positive reaction in the titration based on the strength of the reaction.
- The sum of these scores reflects the total binding strength of the antigen and antibody molecules (known as titration score or avidity).
- Titration is most commonly used for determining
antibody activity and the potential severity of HDFN in alloimmunized pregnant women.
- Titration can be a useful aid in identifying antibodies to certain
high-incidence antigens.
- A titration can distinguish between a characteristic
high-titer, low-avidity antibody (HTLA) and a weakly reactive antibody with a low titer.
- If the autocontrol or DAT is negative and the patient has been transfused or pregnant, then the reactions are likely due to
alloantibodies. Both combinations of multiple antibodies and a single antibody to a high-incidence antigen may cause this pattern of reactivity.
- If the autocontrol or DAT is positive and the patient has not been transfused recently, then the results are likely due to an
autoantibody, either warm reactive, cold reactive, or both.
- If the autocontrol or DAT is positive and the patient has been transfused recently
the results may indicate either an autoantibody or a delayed serological transfusion reaction.
False postives may result from
Pan agglutination or rouleaux
Multiple antibodies
- Certain combinations of antibodies may cause all or most cells tested to react
positively, making antibody exclusion and subsequent identification very difficult
Multiple antibodies
A combination of techniques is usually required to identify
identify the specificity of each antibody present within a complex mixture of them. The technique(s) that should be used depend(s) on which antibodies are suspected.
C. Antibodies to High-Incidence Antigens
Negative autocontrol but almost all positive Screen cells, panel cells, donor RBCs reacting +
Antibodies to High incidence antigens
Testing with rare
Selected cells or plasma treated cells may confirm a + result
Knowning the patients Ethnicity may help
Warm autoantibodies
Warm autohemolytic anemia
positive DAT, with screen, panel, and donor RBCs +
- An antibody that causes all cells tested to agglutinate is called a
Panagglutinatin
Patients with warm autoantibodies tend to have a increase risk of
Alloimmunization compared to the general Population
- If the patient has not been transfused in the last 3 months, an ____________ can be performed and the adsorbed plasma tested for alloantibodies.
Autoabsorption
Cold agglutinins
optimum reactivity between 37.7 and 77.0C
cause problems with a DAT because they can interfere with the detection of more clinically significant antibodies, and interfere with ABO typing
Cold autoantibodies most common types
specificities to I, i, IT, IH, and Pr antigens; autoanti-I is the most common.
Identify using
Cord and Adult RBCs
good indicators of clinical significance for cold-reactive autoantibodies.
antibody titers and thermal amplitude studies
- If cold autoantibodies may be masking alloantibodies, the autoantibodies can be removed from plasma by
autoadsorption using a low temperature or by adsorption with rabbit erythrocyte stroma.
G. Cold Alloantibodies
- Include specificities such as
anti-M, anti-N, anti-P1, anti-P, anti-Pk, anti-Lea, anti- Leb, and anti-Lua.
they rarely cause in vivo hemolysis
you can eliminate the IS, test with Anti-IgG, or eliminate microscopic readings
Prewarm technique
is used to eliminate the effect of Cold reacting auto and allo antibodies but it has show to show a 47% reduction in the performance in these antibodies
Cold agglutinins are shown to be a concern in cardiac bypass surgery because
the patient is constantly in a state of hypothermia
Thermal amplitude and titer are a good indicator for potential complications
If problems arise then the patient can be kept above
Body temperature or plasma exchange may be used to remove the cold autoantibody prior to surgery.
- With a delayed hemolytic reaction the patient exhibits symptoms of
Hemolysis but with serological transfusion reaction the patient does not exhibit symptoms of hemolysis
The reaction pattern will mimic a high frequency antigen but the cross match with donor red cells will be negative
Antibiotic: gentamycin, neomycin, and chloramphenicol
sugars: glucose
dyes acriflavine and tartrazine
Bacteriostatic/ antifungal reagents: paraben, thimerosal, sodium azide
Chemical: citrate, inosine, EDTA
HLA antigens reactions
Febrile, nonhemolytic reactions, and can cause platelet refractoriness.
usually not clinically significant
Plt transfusions may be given to absorb the HLA antigens off the RBC
Antibodies to low incidence antigens
Specificities include Wra, Kpa, Jsa, Cw, Dia, Goa, SC2, Mia, Lua, Cob, and Ytb. Typical patterns of reactivity
The antibody screen is negative but one donor unit is incompatible if an IAT crossmatch is performed.
Screen cells are
O in origin so A and B cells will not react
- Anti-Sda and anti-Lua are characteristic of a
Mixed field reaction
- Consent may be done at the time of admission or it may be obtained separately when the need to transfuse is identified.
Transfusion request forms must be
Verbal or written and have the physician’s name and phone number, the date and time, the phone number, and have the number and amount of test ordered
– ABO typing may be performed at least
twice before transfusing RBCs
When selecting components for ABO typing
The components may be ABO compatible or ABO identical
