Diagnostic Laboratory Services- Cross-matching blood for transfusion
Experience in the practice of veterinary medicine has shown that, perhaps with exception of the horse and the cat, there is little danger from an initial transfusion of blood to domestic animals. However, severe and even fatal reactions may develop upon administration of a second transfusion at a later date or in cases of isosensitisation resulting from transplacental immunisation.
Cross-Matching Donor and Recipient Bloods for Compatibility.
Simple procedures involving a combination of tests for agglutination and haemolysis are available and are within the scope of the veterinary practitioner. In cattle and sheep, the lytic test is required because erythrocytes of these species show little or no natural ability to agglutinate. In the dog and cat, the agglutination technique is applicable, but in the horse both lytic and agglutination testing methods are required, since most equine isoantbodies act as haemolysins.
The method for cross-matching to test for incompatibility by erythrocyte agglutination is outlined below:
- Collect 2ml of EDTA-anticoagulated blood from donor and recipient.
- Centrifuge blood samples for 1 minute in bench top centrifuge at approximately 1,000rpm (ie same speed as for plasma/serum separation) and remove plasma to prelabelled 75 x 10 mm test tubes.
- Make a 2% red cell suspension of each specimen in physiological saline (0.85% NaCl) solution. This can be done by placing 0.02ml of concentrated red cells in 0.98ml of saline solution contained in a 75 x 10mm test tube; mixing, centrifuging, and washing three times; and resuspending washed red cells in a equal volume of saline solution.
- Place two drops of the donor’s cell suspension in a 10 x 75mm test tube and mix. In a second tube similarly place equal volumes of donor’s plasma and recipient’s cell suspension. To check for autoagglutination, set up controls in the manner by mixing donor’s red cells with its own plasma and follow the same procedure with the recipient’s red cells and plasma.
- Shake rack of tubes and incubate for 30 minutes at room temperature, then centrifuge for 1 minute at 1,000 rpm.
- Examine the supernatant for haemolysis. Shake the tubes gently by tapping with finger to detect grossly visible agglutination of red cells.
- If no agglutination is observed, transfer a small amount to a glass slide and examine under the low power of the microscope. A slight haemolysis in canine blood is non-specific. Significant haemolysis and/or agglutination in one or both of the cross-matched tubes but not in the controls indicates and incompatibility and the need to choose a new donor.
