Clinical Pathology: Transfusion Medicine

• Before issuing a red blood cell (RBC) unit, either a serologic or computer crossmatch must be performed. A serologic crossmatch consists of testing a sample of the recipient’s serum or plasma against a sample of donor RBCs from an attached segment on the donor unit to determine if there is ABO compatibility and clinically significant antibodies to RBC antigens present on donor cells.

• The serologic methods used for crossmatch include the immediate spin (IS) or antiglobulin (AHG) crossmatch.

• AHG crossmatch must be performed for patients with a positive antibody screen or a history of a clinically significant antibody.

• A computerized crossmatching system or IS crossmatch may be used for patients with a negative antibody screen and no history of clinically significant antibodies.

• For a computer system to be used to detect ABO-incompatibility, it must meet several requirements:

     1. The computer system must be validated on site to ensure only ABO-compatible whole blood or RBC components have been selected.

     2. Two determinations of the recipient’s ABO group are made, one on a current sample and the second by the one of the following methods: (1) retesting the same sample, (2) testing a second current sample, (3) comparison with previous records.

     3. The computer system contains the unit number, component name, ABO group and Rh type of the component; confirmed donor unit ABO group; two unique recipient identifiers; recipient’s ABO group, Rh type and antibody screen results; and interpretation of compatibility.

     4. A method exists to verify correct entry of data before the release of blood or blood components.

     5. The computer system contains logic to alert the user to discrepancies between the donor ABO group and Rh type on the unit label and those determined by blood group confirmatory tests, as well as to alert the user to ABO incompatibility between the recipient and donor unit.