Blood Transfusion


The crossmatch is defined as a procedure to exclude incompatibility between donor red cells and the patient’s plasma

For babies < 4 months old, a maternal sample is required to check for red cell antibodies

  • If the maternal sample does not contain any red cell antibodies, then Group O Rh D negative red cells can be issued electronically without serological crossmatch.
  • If maternal red cell antibodies are present, then the red cells selected must be compatible with the maternal allo antibodies and a crossmatch using maternal plasma must be performed.


  • For non-urgent cases, samples should be sent to the laboratory at least 24 hours before any transfusion requirement
  • If blood is required urgently, and there is no valid group and save in the laboratory, a full serological crossmatch will take approximately 40 minutes on following receipt of sample in the laboratory.
  • If a patient has been transfused or pregnant within the last 3 months, then the sample is only valid for 3 days, which is from the time the sample is taken to the subsequent transfusion.
  • If a patient has NOT been transfused or pregnant within the last 3 months, then the sample is only valid for 7 days.
  • Where difficulties arise in the provision of blood, the Transfusion laboratory will contact the clinician to discuss further
  • The Transfusion IT system will inform you if there is a valid sample in the laboratory and if the patient is eligible for electronic issue or not, or if a new sample is required.
  • Samples may need referral to NHSBT Filton, Bristol for further investigation
  • This test is performed at GRH and CGH

Sample Requirements

6 mL EDTA tube

6ml EDTA tube

Required Information

Sample and request form must be labelled correctly with 4 points of patient identification reference:

  1. Surname
  2. First name
  3. Date of Birth
  4. NHS or Hospital Number

Unlabelled, wrongly labelled or inadequately labelled specimens will not be accepted. No specimen is considered unrepeatable.

Turnaround Times

Immediate Emergency Group O negative (females) and O positive (males only)

5 mins Electronic issue (providing eligibility criteria met)

15 mins ABO compatible blood

40 mins Fully crossmatched blood


Author: Stuart Lord, Transfusion Practitioner

Reviewed date: 14/03/2023

Next review date: 14/03/2025