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Pre-transfusion tests

Published on 03 September 2021

Pre-transfusion testing establishes the ABO and D blood group of the patient and determines if there are red cell antibodies that could result in an incompatible blood transfusion.

Group and screen

  • "Group and Save" request samples are ABO and Rh (D) grouped and screened for atypical antibodies.
  • Samples are kept for up to seven days depending on the patient's transfusion history.
  • Antenatal samples for booking and 28 week repeat blood are 7 day samples. Samples from women who are or have been pregnant in the past 3 months are 3 day samples.

Crossmatch requests

  • ABO and Rh (D) compatible donor units are selected and crossmatched for named patients and held for that patient until 9am, 48 hours after the date the request was made.
  • If your patient has been transfused, a fresh sample for further crossmatching will be required after 72 hours. You should allow as much time as possible to complete grouping, both antibody screening and cross-matching, in case atypical antibodies are found.
  • If your patient has atypical antibodies, antigen negative blood must be crossmatched serologically. This can mean a delay as further complex investigations may be required to identify and source appropriate units for cross-matching if they are not available within routine stock.
  • We operate a maximum surgical blood ordering schedule (MSBOS). Normally we will crossmatch according to the MSBOS unless the clinician's request gives clear reasons for doing otherwise.

Two sample rule: Group check

Before issuing blood and blood components to a named patient we will compare the blood group on the current sample with the results of any previous tests held on file against the exact patient details.

The majority of patients will have a historical sample. If there is no historical sample or if the blood groups are not the same, a second sample will be requested:

  • the second sample should be taken at a different time - you should re-identify the patient using positive patient ID where possible (“what is your name and what is your date of birth?”)
  • never take two samples at the same time because the patient will only have been identified once

Get in touch with your local transfusion laboratory.