Alert!

• If you need blood urgently, please telephone Blood Bank immediately!
• For emergency transfusions, Blood Bank has various strategies to provide blood as rapidly and as safely as possible. See Emergency Blood
• Group and screen results are only valid at the Blood Bank where the testing was conducted. If your patient has come from somewhere else with a different Blood bank, you will need to send a new sample to your Blood Bank.
• Cord blood samples are not suitable for crossmatching due to the presence of Wharton's jelly.

Blood grouping

• All pretransfusion samples are tested for the ABO blood group and the Rh(D) blood group.
• This is critical for preventing haemolytic transfusion reactions.
• This is typically tested with the antibody screen so takes approximately 40 minutes^# but can be performed separately and faster in an emergency.
• The results of these tests are compared with the patient's previous test results at this and other Blood Banks.
• ABO is tested because all patients will have pre-formed ABO antibodies
• Rh(D) is tested because it is highly immunogenic and the anti-D antibody is highly potent once formed.

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Antibody screening

• All pretransfusion samples are tested for antibodies to the other clinically significant blood groups.
• There are 29 known blood group systems, each with more than one antigen.
• For example, Rh is a blood group system, c, C, D, e and E are antigens within the Rh system.
• This is critical for preventing haemolytic transfusion reactions.
• This is performed by using the red cells from three different donors whose blood groups combined cover the full spectrum of clinically significant blood groups.
• This takes approximately 40 minutes^# and is typically tested simultaneously with the ABO/Rh(D) blood grouping. Because of the nature of the test, testing time cannot be shortened.
• The test takes this long because there is a long incubation period to allow antibodies in the patient's plasma to attach to the donor red cells.
• If the antibody screen is positive, antibody identification is needed.

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Antibody identification

• If the antibody screen is positive, an antibody panel of 11 different donors' red cells is used to identify which antibody is present.
• This is critical for preventing haemolytic transfusion reactions.
• This is typically a manual test and takes approximately 40 minutes^#. Once the antibody has been identified, further time will be required to identify suitable units.
• The test takes this long because there is a long incubation period to allow antibodies in the patient's plasma to attach to the donor red cells.

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Electronic Crossmatching

• If the patient has been blood grouped twice (to exclude any errors) and has no antibodies on antibody screening, blood can be issued immediately by electronic crossmatch.
• This is an electronic crossmatch because the Blood Bank computer system performs a number of crosschecks between the patient's results and the units for issue. If these checks are okay, the units can be issued as fully compatible.
• For patients with no antibodies on antibody screening, blood does not have to be specifically put aside as all the ABO/D group-compatible blood in the bank is immediately available for issue.

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Serological Crossmatching and Antigen Matching

• Where a patient has antibodies identified on screening, a full crossmatch is needed.
• A full crossmatch involves mixing the patient's plasma with red cells from the unit and looking for a reaction.
• The test takes 40 minutes^# because there is a long incubation period to allow antibodies in the patient's plasma to attach to the unit's red cells.
• Multiple units can be crossmatched at a time, but Blood Bank will need to know how many are required to decide how many units to test.
• Where a patient has antibodies identified on screening, only fully crossmatch units can be issued as fully compatible.
• For some antibodies, a further step is also required, namely confirming that the unit red cells are negative for the antigen that the antibody is directed against.

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Note (#):

• Times provided above are the minimum time required to perform the test and do not include associated tasks.
• The time to complete the test also varies depending on workload and case priorities.

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