Blood Group or Crossmatch Test

 

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

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

How the Test is Performed

Blood Group or Crossmatch requires a small tube of blood from a vein. It is of utmost importance that this specimen is labelled correctly, to ensure that the sample can be positively identified by the lab, and that the carefully matched donor blood is given to the right patient. The “Blood Bank” will reject incompletely labelled samples.

Medical Conditions and Symptoms

A Crossmatch may be requested when a blood transfusion is anticipated, under these circumstances:

  • 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

Blood Group only, without crossmatch, may be done:

  • 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

Test Results Explained

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).
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. See Rhesus Antibodies test.

Crossmatching is the process of testing a patient’s blood against a potential donor sample, to find a match of compatibility. This usually takes about 30 to 60 minutes. If blood is urgently required for immediate transfusion, the laboratory may issue un-crossmatched, group-specific blood (eg A-positive blood for an A-positive recipient), or O-negative blood may be given, because this is the “universal donor” bloodgroup (although not entirely free of potential problems).

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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