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.

[2]: 263  Cross-matching is also used to determine compatibility between a donor and recipient in solid organ transplantation including heart/lung transplation.

It is an immediate test that involves combining the patient's serum and donor's red blood cells at room temperature, then centrifuging the sample and observing for agglutination or hemolysis.

[2]: 261 The AHG crossmatch is done by incubating the recipient serum/plasma with the donor's red blood cells and adding anti-human globulin.

In an emergency, blood grouping can be done easily and quickly in 2 or 3 minutes in the laboratory on glass slides with appropriate reagents, by trained technical staff.

This method depends on the presence or absence of agglutination (clumping of red blood cells), which can usually be visualized directly.