Antibodies to hydrocortisone in reagent red cells causing positive antibody screening tests

When a patient's serum contains a temperature-independent antibody reacting with all antibody screening and antibody identification panel cells but with few or no units of blood used for crossmatching, one should suspect an antibody against a constituent of the suspension medium of the reagent blood cells. This observation is confirmed by negative reactions with a) washed reagent cells or b) another manufacturer's cells that do not contain the same additives. Two patients are described with antibodies to hydrocortisone that are present in one manufacturer's antibody screening cells and identification panels. The hydrocortisone was added by the manufacturer to prevent hemolysis of the reagent red cells. The patient's antibodies were IgM, complement independent, and nonneutralizable by prior incubation with hydrocortisone. The addition of hydrocortisone to other manufacturers' reagents converted previously negative reactions to the same level of positivity as was seen with the reagent from the index manufacturer. Antibodies to reagent constituents can cause delays in finding compatible blood. It is suggested that manufacturers delete irrelevant additives or those of questionable necessity from their reagents.