Crossmatching before a second transfusion in dogs
9-year-old crossbreed dog with chronic non-regenerative anaemia. Three weeks ago it received packed red cells from a DEA 1-negative donor without incident. Its haematocrit is now 13% and it needs another transfusion.
What should you do before transfusing?
chevron_right Show answer and explanation
A. Nothing further: if the donor is DEA 1-negative, the transfusion is safe
DEA 1 typing avoids the most immunogenic antigen, but the first transfusion may have sensitised the dog to other antigens (DEA 7, Dal and others) that typing does not detect.
B. Perform a major crossmatch between donor red cells and recipient plasma
Correct. From about 4–5 days after a transfusion, the dog may have developed alloantibodies. The major crossmatch detects recipient antibodies against donor red cells and is mandatory in previously transfused dogs.
C. Perform only a minor crossmatch
The minor crossmatch tests donor plasma against recipient red cells and is of little relevance with packed red cells. The risk lies in the recipient's antibodies.
D. Premedicate with antihistamines and corticosteroids instead of testing
Premedication does not prevent acute haemolytic reactions and its benefit even against allergic reactions is debated. It does not replace crossmatching.
lightbulb Key takeaway
In dogs, a first transfusion with DEA 1-typed blood is usually safe without crossmatching; from about 4 days after any transfusion, always perform a major crossmatch. A compatible crossmatch does not guarantee red cell survival or prevent delayed reactions.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.