Crossmatching Blood Groups

What is a blood group?

Blood group is the characterisation of blood type by the ABO system (A, B, AB, or O), and also includes the Rhesus typing (positive or negative).

What is crossmatching?

Crossmatching is the process of testing a patient’s blood against a potential donor sample, to find a match of compatability.

How is crossmatching performed?

Crossmatching requires a small tube of blood from a vein. The blood is then tested against the donor sample for compatibility, which takes about 30 to 60 minutes.

If blood is urgently required for immediate transfusion, the laboratory may issue un-crossmatched, group-specific blood, for example A-positive blood for an A-positive recipient.

Alternatively, O-negative blood may be given, because it is considered the ‘universal donor’ bloodgroup. However it is not entirely free of potential problems.

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When would you need a crossmatch?

A crossmatch may be requested when a blood transfusion is anticipated, such as:

  • Severe bleeding is occurring, for example due to major trauma, or internal bleeding from the bowel or stomach
  • Severe bleeding may occur, for example when major surgery is planned
  • Severe anaemia (low haemoglobin or blood count) is present

A blood group without crossmatch may be performed:

  • Routinely in pregnancy
  • To confirm Rhesus status in a pregnant woman, when there is a risk of Rhesus sensitisation – for example following an injury to the abdomen, or vaginal bleeding due to a threatened miscarriage. See Rhesus Antibodies test
  • Rhesus (Rh)-negative women are a special case in pregnancy; to avoid Rhesus iso-immunisation they may require treatment with anti-D immunoglobulin in a variety of circumstances.

Related specialists

Related procedures

  • Blood Test (venesection)
  • Intravenous Cannulation
  • Blood Transfusion

Related tests

Also known as

  • Group and Hold (G&H)
  • X-Match



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This article is for informational purposes only and should not be taken as medical advice. If in doubt, HealthEngine recommends consulting with a registered health practitioner.

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