What is the rule of 3 in antibody identification?
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A standard antibody identification panel comprises reagent red cells from at least 8 group O donors. The panel should support resolution of as many common antibody mixtures as possible. Show
Not all Antibodies are Significant
Step 1: ignore clinically insignificant antibodies. These are typically antibodies which do not react at 37°C. Look for the Agglutination Pattern
Step 2: note the agglutination pattern (i.e., panel cells which react with the patient’s plasma) and look for common expressed antigens. These antigens should not be expressed on cells with no reaction with the patient’s plasma. This gives an idea of the possible antigen target of the culprit antibody. However, exclusion of other antibodies is required for confirmation. In the example, the antibody is likely to be anti-E because cells 3 and 6 express it, corresponding to the reactive IAT. Antibodies such as anti-c and anti-k are not likely candidates because c and k are expressed by panel cells with no reaction (e.g. cells 4, 5, 7, 8, 9). Excluding Other Clinically-Significant Antibodies
Step 3: take note of panel cells with no reaction with the patient’s plasma.
Step 4: exclude antigens on panel cells which have no reaction with the patient’s plasma. Since they do not cause agglutination with the antibody in the plasma, they can be safely excluded the target of the culprit antibody. When excluding antigens, exclude them on cells which are homozygous for the antigen in question. This ensures that weaker antibodies which exhibit dosage effects are not inadvertently ruled out. Exceptions can be made for anti-K, which is very rarely homozygously expressed. In the example, anti-D can be excluded because cells 1, 2 and 3 are express the D antigen, yet have no reaction with the patient’s plasma.
Step 5: exclude all other antibodies by checking each antigen. A minimum of two (ideally three) cells which are homozygous for the antigen in question should be used to exclude it. In this example, all clinically-significant antibodies except anti-E have been excluded. Antibody Specificity
Step 6: assign the specificity of the antibody. This should only be done once two cells expressing the antigen react with the patient’s plasma (red box), and two cells which do not express the antigen are non-reactive with the patient’s plasma (green box). Technically, confirmation should include phenotyping of the patient’s own red cells, to ensure that they are antigen-negative for the alloantibody target (alloantibodies should not form against self-antigens). In this example, cell 3 has a strong 4+ reaction at the IAT phase, while cell 6 has a weaker 2+ reaction. This is likely due to a dosage effect, since cell 4 is homozygous for E (DcE/DcE), while cell 6 is heterozygous (dcE/dce).
Step 7: check that the antibody identification results do not conflict with the results from the antibody screen. This guards against mistakes made by inadvertently carrying out antibody identification on the wrong sample. What is rule out technique in antibody identification?Rule-out (also referred to as exclusion or cross-out) is a process by which antibodies are identified as being unlikely in a given sample due to the absence of an expected antigen-antibody reaction. In other words, the absence of a reaction is noted with a cell that is positive for the corresponding antigen.
What is the 3 3 rule ascertain quizlet?The 3+3 rule ascertains correct identification of antibody at a confidence level of 95%. For this level to be met, reagent red cells are found containing target antigen to suspected antibody that react in test phase; likewise, reagent red cells devoid of antigen will not react in test phase.
What is antibody identification test?An RBC (red blood cell) antibody screen is a blood test that looks for RBC antibodies in your blood. These antibodies destroy red blood cells that are different from your own (foreign). Having RBC antibodies won't harm your health, but: If you have a blood transfusion, they could cause serious illness.
What are the important considerations that you have to remember in antibody identification?Two important things to remember about antibody screening: Group O red cells are used to avoid interactions with ABO antibodies. Any incompatibility with the screen cells should be due to antibodies other than normally occurring ABO antibodies.
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