When performing an antiglobulin test, why must the lab technician wash the red blood cells before adding the AHG reagent?

Washing the red blood cells before adding the antihuman globulin (AHG) reagent is vital because this step removes unbound serum globulins that could interfere with the test results. When performing the antiglobulin test, the presence of unbound immunoglobulins may lead to false-positive results by reacting with the AHG reagent and misleadingly indicating that a reaction is occurring when it is not. Therefore, thoroughly washing the cells ensures that only the IgG antibodies (or other relevant antibodies) that are specifically bound to the red blood cells are retained, allowing for accurate detection when the AHG reagent is added. This ensures that any agglutination observed in the test is a true positive result, reflecting specific interactions between the bound antibodies and the AHG.