crossmatchning

Crossmatching is a laboratory test used to assess the compatibility of donor red blood cells with a recipient’s plasma, with the aim of preventing immune-mediated transfusion reactions. It is a key step in transfusion medicine and is sometimes used in solid organ transplantation to evaluate the risk of antibody-mediated rejection. The test relies on detecting antibodies in the recipient that could target donor red cell antigens, or in some contexts, donor antibodies that could affect the recipient.

The main types of crossmatching are major crossmatch and minor crossmatch. The major crossmatch mixes the recipient’s plasma or serum with donor red blood cells to detect antibodies that could cause hemolysis of the transplanted cells. The minor crossmatch uses donor plasma or serum with recipient red blood cells to identify antibodies that might react with recipient cells. Electronic or computer-assisted crossmatching uses stored donor antigen data and the recipient’s antibody profile to determine compatibility without a physical mixture of cells, under appropriate safety conditions. Flow cytometry crossmatch is a more sensitive method that can detect low levels of antibodies by measuring binding of recipient antibodies to donor cells using fluorescent labeling.

In practice, crossmatching can be performed by immediate spin (IS) testing, antiglobulin (AHG) testing, or a combination, and may be supplemented by flow cytometry for higher sensitivity. If a crossmatch is compatible, transfusion proceeds with the chosen donor unit; if incompatible, alternative donor units or antigen-matched units are sought. Limitations include the inability to predict all non-immune transfusion reactions and the influence of recent transfusions, autoantibodies, or complex alloantibody profiles on interpretation.