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31 Cards in this Set
- Front
- Back
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antibody screen |
the test used to detect antibodies |
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antibody screens are used for |
patients needing a transfusion pregnant women patients who have had transfusion reacctions blood and plasma donors |
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unexpected antibodies |
found in addition to the expected anti-A or anti-B antibodies result of RBC stimulation (transfusion, HDFN) may be clinically significant (IgG), not clinically significant (IgM) |
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What is the autocontrol? |
Tests the patient's serum with their OWN RBCs, used to detect autoantibodies |
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How are DAT and Autocontrol similar? |
Both are used to determine if antibodies against patient or transfused cells are present |
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How are DAT and Autocontrol are different? |
DAT uses patient cells with AHG to test for alloantibodies Autocontrol uses patient cells with patient cells to test for autoantibodies |
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Why is patient information like transfusion history/pregnancy/age/race/diagnosis important? |
-Mixed RBC populations from a previous transfusion can remain for up to 3 months -Patient could have come from a different hospital -Some diseases are associated with with certain antibodies -Race can determine what antibodies occur at a higher frequency |
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Describe the reagent RBC panel and antigram with regard to antigen configuration and ABO type |
The antibody panel is an extended version of the antibody screen Uses group O reagent cells with phenotypes for most common antigen specifies Initial testing of the panel cells use the same potentiators as those in the initial antibody screen An autocontrol is included |
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Define the phase of reactions and its significance |
Phase is defined as the environment in which the agglutination reaction occurs, this determines antibody class IgM antibodies react at room temp IgG antibodies react at body temp or during immediate spin |
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Discuss how the reaction strength contributes to antibody resolution |
Strength of an antibody reaction clues to the number of antibodies present Reactions with varying strength indicate multiple antibodies present Strength can also be affected by dosage (if panel is homozygous a stronger reaction may occur - weak antibodies may not even react with heterozygous antigen expression) |
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Describe the process of ruling out antibodies on a panel |
Panel cells that are negative in all phases can be used to rule out antibodies Starting at the first negative panel cell eliminate any antigens present Panel cells that are heterozygous should not be ruled out as the reaction may be too weak to observe |
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What antibody CAN be ruled out heterozygously? |
Kell |
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Explain the rule of three with regard to antibody identification |
Used to ensure accuracy, 3 antigen-positive cells must react and 3 antigen-negative cells must not react with patient's plasma or serum |
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When are additional panel cells, AKA selected cells used? |
If the rule of three is not followed by any of the tested antibodies |
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What are the methods that can be used when working with multiple/high frequency antibody/antibodies |
Selected cells, proteolytic enzymes, or chemicals like dithiothreitol |
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Describe the properties of a high titer, low avidity antibody, and techniques for identifying or avoiding reactivity |
An antibody that reacts with high incidence antigens can have a characteristic high titer, low avidity pattern Tend to react at the AHG phase, but are inconsistent, and are not usually enhanced with other potentiators They are not implicated in causing transfusion reactions or HDFN Removed by titration or inhibition |
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Explain the importance of a control when performing antibody neutralization |
Control is untreated diluted patient's serum, indicates that negative reactions following neutralization are due to the elimination of antibody reactivity and not by dilution of the antibody in question |
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Discuss the potential problems with the prewarming procedure |
Prewarming can reduce the strength of clinically significant antibodies that are masked by the cold antibody Washing with warm saline after 37C incubation is not recommended, can result in the complete removal of clinically significant antibodies |
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What are the six methods of enhancing weak IgG antibodies? |
1.Repeat with a different enhancement such as enzymes/PEG 2. Check antigen dosage on weak or missing reactions 3. Select different cells from a new panel 4. Incubate longer 5. Phenotype if not recently transfused 6. Increase serum to cell ratio (within limits of reagents) |
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Explain the process of identifying the specificity of a cold autoantibody |
Use a cold panel, set of selected reagent red cells that aids in determining anti-IH, cord blood is used as negative for I antigens |
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Explain the technique of avoiding cold autoantibody reactivity |
Use a monospecific IgG AHG reagent rather than a polyspecific reagent Skip immediate spin crossmatching and test at 37C Use 22% bovine serum albumin instead of LISS Prewarm tubes to 37C Use adsorption techniques |
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What are 4 different adsorption techniques? |
Rabbit erythrocyte Stroma (RESt) Cold Autoadsorption Warm Autoadsorption Differential (allogenic) Adsorption |
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Rabbit Erythrocyte Stroma |
Removes cold IgM antibodies, specially Anti-I Limitations - possibility of adsorption of anti-B or other IgM antibodies |
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Cold Autoadsorption |
Patient red cells are used to remove cold autoantibodies to determine presence of alloantibodies DO NOT USE IF RECENTLY TRANSFUSED |
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Warm Autoadsorption |
Patient red cells are used to remove warm autoantibodies to determine presence of alloantibodies DO NOT USE IF RECENTLY TRANSFUSED |
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Differential (allogenic) Adsorption |
Use known phenotyped red cells to separate specificity, warm autoantibodies from alloantibodies or alloantibodies with several specifies Limitation - May absorb alloantibody to a high frequency antigen |
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Define the elution procedure |
The eluate (recovered antibody) is used in an antibody panel to identify it Performed in cases of suspected HDFN and may not be reactive in all cases of warm autoantibodies |
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What are the methods of elution? |
Glycine acid, Physical removal, organic solvents |
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Glycine Acid |
Lowers pH, rapid and sensitive, commercially available |
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Physical antibody removal |
Heat/Freeze/Thaw, rapid, effective for ABO antibodies, inexpensive, NOT sensitive for antibodies other than ABO |
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Organic solvent |
Antibody removal by Ether/Methylene/Chloride/Chloroform, sensitive and inexpensive, HAZARDOUS, CARCINOGENIC, FLAMMABLE |
