Why Is My Dog Or Cat’s ANA Test Positive?

Ron Hines DVM PhD

See What Normal Blood & Urine Values Are

Causes Of Most Abnormal Blood & Urine Tests

See How Tests Are Grouped

Anti-nuclear Antibody = ANA, ANF

This is not a commonly run test. Your veterinarian may decide without ordering it that your dog or cat has an autoimmune health issue based on his/her physical examination, other in-office tests run or the absence of any other likely explanation for your pet’s health issue. The ANA test measures factors similar to the Coombs test – evidence that your cat or dog is producing antibodies against its own tissue (in this case, antibodies against various components of the nucleus of its own cells). (read here) These are called autoimmune reactions. In humans, many of the conditions that produce ANA antibodies are lumped together as forms of “lupus”.

A small elevation in ANA test results is not necessarily something to worry about.  As pets and people age, the number of these self-directed blood antibodies moderately increase in all of us. (read here)

Health Problems That Might Increase The ANA Level In Your Pet:

The ANA test is quite sensitive. But it is not specific for any one disease. It can only used as one factor your veterinarian will consider in making an autoimmunity diagnosis. Your dog or cat’s cell nuclei contains thousands distinct proteins and its immune system, when it malfunctions, can produce antibodies to any one of them. Depending on which nuclear protein is stimulating the autoantibodies in your pet or in a human, the disease receives a distinct name. ANA is often elevated in: Systemic lupus erythematous (SLE), autoimmune polyarthritis, pemphigus vulgaris and autoimmune thrombocytopenia.  Immune-mediated hemolytic anemia, immune-mediated thrombocytopenia and polyarthritis are the most common forms in dogs (read here  & here) Less is known about these diseases in cats. (read here)  Although not identical in meaning, erythematous can also be described as erythematosus.

ANA Titer (level) can also be elevated in many chronic inflammatory and infectious diseases of dogs and cats that are not primarily autoimmune in nature – diseases such as ehrlichiosis,    bartonellosis and babesiosis.  A few dogs and cats have an increase in their ANA levels without veterinarians ever discovering what the underlying disease, if any, might be  – particularly as they age. Converting to a positive ANA status can also occur post-vaccination. That is particularly true after receiving vaccines containing leptospirosis antigens or subsequent to a natural case of leptospirosis. (read here

The Diagnostic Laboratory of the University of Georgia Veterinary School puts little faith in the value of the ANA test in animals. Quoting their website:  “There is no consensus as to what is a significant ANA titer in animals might be. Many investigators feel that titers >10 are significant while others feel that titers > 40 are significant. A negative result does not rule out systemic lupus erythematosus or other immune-mediated diseases as these conditions can occur without detectable antinuclear antibodies”


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