With respect to transfusion, timeliness of evaluation can be essential for the patient. The following guidelines are invaluable for conducting comprehensive and efficient antibody identification. Much like a detective narrowing down suspects, you should utilize multiple criteria to guide you toward the most likely interpretation of the antibody. These tips will assist you in this process.
Relevant patient information should include clinical history and demographics which can provide valuable information in an antibody identification investigation. For example, some antibodies are associated with a particular race or ethnicity. Transfusion or pregnancy history are helpful to determine if the antibody is naturally occurring or immune.
The antibody screen can provide sufficient data to make initial hypotheses regarding the likely antibody specificities and may be useful to presumptively rule-out some antibody specificities. When analyzing the antibody screen data, take into account the:
- strength/characteristics of reactions (for example, mixed-field or weak versus strong)
- phase of testing (for example, room temperature versus AHG)
- pattern of reactivity (which cells react and which do not)
These are important factors that will provide clues about the possible identification of the antibody(ies). Many antibodies exhibit
dosage, that is, they react more strongly with homozygous cells than with heterozygous cells. Antibodies that can display dosage are Duffy, Kidd, Rh, and MNS blood groups.
If a tube method is used, reactions can be read at immediate spin, 37°C, and AHG phase. Most facilities will only perform agglutination readings at AHG for routine antibody screening. If a gel method is used, reaction readings are always done at the AHG phase.
- Reactions occurring only at the immediate spin phase could indicate a possible IgM antibody, cold agglutinin, or rouleaux.
- Reactions occurring in the 37°C and/or AHG phase could indicate a possible IgG antibody.
- Reactions occurring in both reaction phases could indicate a combination of both IgM and IgG antibodies or a strong IgM antibody that carries through to the AHG phase.
The presence of multiple antibodies should be considered if reactions vary in strength or if there are two separate reaction patterns in the IS and AHG phases.
