Resolving ABO discrepancies
Confirming a patient’s medical history (eg., of an ABO-incompatible stem cell transplantation, or of recent transfusion of non-ABO identical blood products) will often provide sufficient information to resolve a discrepancy.
In patients who type as A in their forward type but appear to have an anti-A in their reverse type, the use of the Dolichos biflorus lectin, which acts as an anti-A1 lectin, can be used to confirm if the patient has a type A subtype, as A1 cells will agglutinate in presence of Dolichos biflorus but non-A1 cells will not.
Washing of cells can remove excess protein from the patient’s plasma, which may be causing rouleaux and which may macroscopically resemble agglutination, can eliminate artefactual reactions.
Warming of the sample can remove interference due to non-specific agglutination from cold agglutinins. However, it is important that the specificity of a cold agglutinin be identified before it is pre-warmed away in an antibody screen, as pre-warming can sometimes eliminate clinically significant antibodies.
Next page: Methods of Testing