The “anti-human globulin (AHG) crossmatch” is a type of serologic crossmatch used in patients who do not qualify for either the computer/electronic or immediate-spin crossmatch. In general, patients with clinically significant antibodies require extra testing to be as sure as possible that serum is compatible with the donor’s red blood cells. The AHG crossmatch is done by incubating the recipient serum/plasma with the donor’s red cells and adding anti-human globulin reagent to detect any antibody coating of the donor red cells. It is really just an indirect antiglobulin test (IAT). Alternate names for the AHG crossmatch include “full” crossmatch, “IAT” crossmatch, or “Coombs” crossmatch.