Pretransfusion compatibility testing

Compatibility testing is important to prevent transfusion of incompatible donor red cells that might result in a haemolytic transfusion reaction. (1-3)

A Type and screen (also known as group and hold) includes the following:

  • Confirmation that patient details on blood sample and request form are identical.
  • Checking historical information on patient such as previous blood group, previous transfusion and obstetric history
  • ABO and RhD typing of recipient's red cells
  • Antibody screen to detect antibodies in recipient's plasma
  • Identification of red cell antibodies (performed if positive antibody) screen detected
  • Crossmatching appropriate donor red cells

Crossmatch

Crossmatching is used to confirm compatibility between the patient's blood (plasma) and the donor red cells. This may be performed by either serological or electronic methods.

  • Indirect antiglobulin technique (IAT)

    • Generally used when crossmatching for patients with clinically significant IgG antibodies.

    • Patient's plasma is incubated with donor red cells and tested.
  • ​Immediate spin crossmatch
    • Designed to detect ABO incompatibilities between donor red cells and recipient plasma.
    • Only used if patient currently has no clinically significant antibodies, and there is no history of clinically significant antibodies.
    • Patient's plasma is tested against donor red cells.
  • Electronic (Computer) crossmatch
    • ABO compatibility of patient and donor red cells is checked by the laboratory information system (LIS) with no serological crossmatch tests needing to be performed.
    • Only used if patient currently has no clinically significant antibodies, and there is no history of clinically significant antibodies.
    • Allow red cells to be issued with minimal delay once blood group and antibody screen completed.
    • Specific criteria must be met in order to utilise electronic crossmatching (refer to ANZSBT guidelines).
  • Sample validity refers to the period when a pretransfusion sample may be held for testing and used to provide crossmatched blood.
  • Sample validity period depends on the patient's transfusion and obstetric history. Red cell antibodies can rapidly appear in response to stimulation by transfused red cells or as a result of pregnancy.
  • If the patient has been transfused with red cells, or is currently (or has been) pregnant in the 3 months preceding pretransfusion sample collection, the sample will have a validity of 72 hours. This is known as the 72-hour rule.
  • A new sample will need to be collected once 72 hours elapses if further transfusion is required.
  • Longer expiry times are often applied if the patient does not have a history of transfusion or pregnancy.
  • Contact your transfusion service provider for their policy on sample retention.
References
  1. Australian and New Zealand Soceity of Blood Transfusion. Guidelines for pretransfusion laboratory practice. Australia, NSW 2007. 
  2. Milkins C, Berryman J, Cantwell C, Elliott C, Haggas R, Jones J, on behalf of the British Committee for Standards in Haematology. Guidelines for pre-transfusion compatibility procedures in blood transfusion laboratories. Transfusion Medicine 2013;23:3-35.
  3. AABB. Technical Manual, 18th ed. USA, 2014.