Why Is My Dog Or Cat’s Blood Autoagglutination Test Positive?

Ron Hines DVM PhD

To see what normal blood and urine values are for your pet, go here

For an explanation of causes of most abnormal blood and urine tests go here 

To see how tests are often grouped, go here

Autoagglutination Positive Blood Samples

When your dog or cat produces defensive antibodies against its own red blood cells, it has developed a form of autoimmune disease; in this case, autoimmune hemolytic anemia. One characteristic of these antibodies is that they often cause the red blood cells in a thin film of your pet’s blood to form beads and clumps (as they did on the slide in the photo above).

Both dogs and cats can develop autoimmune anemias. Old English sheepdogs, Irish setters, cocker spaniels and poodles seem a bit more susceptible to the problem – but any breed can develop it.

Autoimmune anemia is also thought to occur due to one or more “triggers” in dogs and cats that have a genetic susceptibility to the problem. Those triggers are thought to include chronic inflammations, drug reactions, infectious organisms and, perhaps, vaccines – things that cause your pet’s immune system to “sit up and take notice“.

This test is sometimes performed by swirling a drop of the pet’s blood on a glass slide or , just as commonly, observed accidentally as blood is being processed by your veterinarian for analysis.

Agglutination in the presence of antibody is also used as a crude basis for cat blood donor compatibility with the recipient cat before a cross-transfusion is considered.

Cats that are infected with Mycoplasma haemofelis (formerly called  Haemobartonella felis) as well as dogs with  babesiosis can also be auto-agglutination positive.

Complementary tests:

CBC and blood chemistry panel, red blood cell morphology (anisocytosis, poikilocytosis, RDW) , reticulocyte count, blood globulin levels, Coombs test, ANA test, AG ratio


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