• EDTA (plasma): more suitable for automated systems, but may miss weak, complement-binding antibodies
  • Clotted samples (serum): haemolysis can indicate a positive reaction in the reverse group or IAT.
    • Serum samples are recommended wherever possible for investigation of transfusion reactions as they are better at identifying weak antibodies such as Jka, which might be detectable only by the complement bound to red cells.
  • Laboratories  should have a sample acceptable policy covering the labeling and condition of samples.
  • Samples must not be taken more than 3 days from the date of anticipated transfusion, to ensure that it is representative of the recipient’s current immune status. This is especially true when the recipient has been transfused or pregnant within the last 3 months, or that information is unknown.
  • For patients not transfused or pregnant within the last three months, there may be deviation from the 3-day rule (see table below).
PatientWhole blood
at room temp
Whole blood
at 2 – 8°C
Plasma at -30°C
Not pregnant and not transfused
in the last 3 months
48 hours7 daysN/A
Pregnant or transfused
in last 3 months
48 hours3 days3 months
Working Limits (Time blood is Taken to Time of Transfusion) of Stored Blood Samples for Specific Patient Types
  • Samples should be retained for at least three days post-transfusion, so as to allow for re-testing should haemolytic transfusion reactions occur.
    • Plasma samples should be kept for at least 7-14 days post-transfusion to allow for investigation of any possible delayed haemolytic transfusion reaction.
  • These samples should be stored in a way that minimises the risk of an out-of-date sample being selected for pre-transfusion testing.

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