Crossmatch

A crossmatch is performed to establish compatibility between a unit of donor blood and the intended patient's blood. The following blood components need to be crossmatched prior to transfusion: 

• Whole blood 
• Red blood cells
• Leukocyte poor packed red blood cells 
• Washed packed red blood cells 
• Granulocytes 

The following information must be included with a crossmatch request: 

• Component desired. 
• Number of units needed. 
• Transfusion priority: Hold, Give, Surgery.
• Date of transfusion or surgery.

If no clinically significant antibodies were detected in the antibody screen (see Antibody Screen), only serologic testing to detect ABO incompatibility is required. ABO compatibility can be verified electronically via a validated, on-site computer system provided acceptable criteria have been met. Electronic crossmatching eliminates the need for a serologic crossmatch, which reduces sample volume requirements and testing time. Two determinations of the recipient’s ABO grouping must be on file, one of which is from the current specimen collection. The confirmatory ABO grouping may be from historical records or from an additional collection. The recipient must not have detectable clinically significant antibodies or a history of antibody. The laboratory information system (LIS) must contain donor unit information to include the donation identification number, component name, ABO group, Rh type, donor confirmation typing, and the interpretation of compatibility with the recipient. A method must exist to verify that data entry is correct prior to the release of blood components. In addition, the LIS must contain logic that alerts the user of any discrepancies between recipient records and the donor unit.

If a clinically significant antibody has been detected, an antiglobulin crossmatch is required. The donor unit selected should be antigen-negative for the corresponding alloantibody identified. The antiglobulin crossmatch consists of an immediate spin crossmatch with the recipient’s plasma and cells from the donor unit. The test system is then incubated at 37°C and completed with the antiglobulin test. Antiglobulin crossmatching may be performed in tube tests, typically with the addition of LISS or PEG enhancements or in column-agglutination and solid-phase red cell adherence tests. Observable reactivity and/or hemolysis at any phase of testing indicate incompatibility. Subsequent testing should include an antiglobulin testing phase and the addition of an autocontrol to identify the cause of the reactivity.

In an emergency, the patient's physician must weigh the risk of transfusing uncrossmatched blood against the hazard of waiting for a completed crossmatch. If the physician believes the urgency of the situation warrants the use of uncrossmatched blood, they are asked to sign an Emergency Blood Release Form to document the reason for the urgent need and to acknowledge that units are not crossmatched at the time of transfusion. Direct consultation with Blood Bank personnel is highly recommended to expedite requests. Two options are available for emergency transfusion. O-negative red cells are available for immediate transfusion to any patient, but should be used only when the patient's blood type is not known and there is insufficient time for typing. This situation will sometimes occur in the trauma setting and should only apply to the first few units given. The preferred medical practice is to transfuse ABO type-specific blood rather than O-negative red cells whenever possible in order to conserve the O-negative blood supply and to minimize transfusion of potentially incompatible group O plasma. Blood typing can be completed and type-specific blood made available within 5 minutes after receipt of a patient sample. Blood type cards or dog tags from other facilities are not acceptable documentation of blood type. 

In all emergency situations, standard compatibility testing for units issued uncrossmatched is initiated and completed without delay and additional crossmatched blood is made available as soon as possible. If any compatibility problem is detected during follow-up testing, the physician is notified immediately.

Specimen requirement for a crossmatch is 2 plain red-top tubes of blood (15 mL minimum).  The specimen must be labeled with patient's full name, birth date, date of collection, and phlebotomist’s initials.

Reference

Milkins C et al, British Committee for Standards in Haematology, Guidelines for pre-transfusion compatibility procedures in blood transfusion laboratories, Transfusion Med, published online December 6, 2012, doi: 10.1111/j.1365-3148.2012.01199.x