Coombs test in the context of "Robin Coombs"

Cross-matching or crossmatching is a test performed before a blood transfusion as part of blood compatibility testing. Normally, this involves adding the recipient's blood plasma to a sample of the donor's red blood cells. If the blood is incompatible, the antibodies in the recipient's plasma will bind to antigens on the donor red blood cells. This antibody-antigen reaction can be detected through visible clumping or destruction of the red blood cells, or by reaction with anti-human globulin. Along with blood typing of the donor and recipient and screening for unexpected blood group antibodies, cross-matching is one of a series of steps in pre-transfusion testing. In some circumstances, an electronic cross-match can be performed by comparing records of the recipient's ABO and Rh blood type against that of the donor sample. In emergencies, blood may be issued before cross-matching is complete. Cross-matching is also used to determine compatibility between a donor and recipient in solid organ transplantation including heart/lung transplation.

In immunology, the term sensitization is used for the following concepts:

• Immunization by inducing an adaptive response in the immune system. In this sense, sensitization is the term more often in usage for induction of allergic responses.
• To bind antibodies to cells such as erythrocytes in advance of performing an immunological test such as a complement-fixation test or a Coombs test. The antibodies are bound to the cells in their Fab regions in the preparation.
• To bind antibodies or soluble antigens chemically or by adsorption to appropriate biological entities such as erythrocytes or particles made of gelatin or latex for passive aggregation tests.

Those particles themselves are biologically inactive except for serving as antigens against the primary antibodies or as carriers of the antigens. When antibodies are used in the preparation, they are bound to the erythrocyte or particles in their Fab regions. Thus the step follows requires the secondary antibodies against those primary antibodies, that is, the secondary antibodies must have binding specificity to the primary antibodies including to their Fc regions.