Antinuclear antibodies (ANA) in cats and dogs
Antinuclear antibodies (ANA) are antibodies the body makes against parts of its own cell nuclei, such as DNA and histones. The test is used to support a diagnosis of systemic lupus erythematosus (SLE), a rare autoimmune disease. It is sensitive but not specific: a positive result also appears in other illnesses and in some healthy animals, so it is read only together with the signs and other tests.
What it shows
In SLE the immune system makes many antibodies against the body’s own tissues, and immune complexes settle in joints, skin, kidneys and other organs. ANA are the diagnostic hallmark of the disease. That is why a vet orders this test when an animal has a combination of problems such as joint inflammation in several joints, skin disease, protein in the urine or a low platelet count.
The lab dilutes the serum step by step and puts each dilution on a tissue rich in cell nuclei. Antibodies that stick to the nuclei are made visible with a fluorescent marker under the microscope (indirect immunofluorescence). The test needs a reagent made for the species, so it is offered for dogs and cats. The report may name a staining pattern — homogeneous, speckled or nucleolar; in dogs these patterns do not point to a particular antibody or disease.
Higher than reference — what it may be a sign of
- Higher titer with matching signs. In dogs, titers from 1:80 upwards are more likely to reflect SLE when the clinical and laboratory picture supports it. ANA supports a diagnosis of SLE, but the diagnosis rests on the whole clinical syndrome — signs such as skin disease or polyarthritis and findings such as protein in the urine or low platelets.
- Low positive titer. In dogs, titers up to 1:40 are often nonspecific: they appear in older dogs and in various inflammatory and infectious diseases.
- Infections. Ehrlichiosis and bartonellosis are among the infections that can give a positive ANA without SLE.
- Other immune-mediated disease. Dogs with immune-mediated non-regenerative anaemia often have raised ANA titers, usually below 1:160, without having SLE.
- Healthy animals. Some healthy animals have ANA.
Lower than reference
A negative ANA argues strongly against active SLE. It does not rule out other immune-mediated diseases — for example immune-mediated polyarthritis or anaemia — which are recognised by their own tests. Some animals with SLE have no detectable ANA, so the diagnosis rests on the whole clinical picture rather than on one result.
Look at together with
- Platelets and the red cells, with the Coombs test — immune-mediated haemolytic anaemia, low platelets or both are the most common presentations of SLE in animals.
- Urine protein and the UPC ratio — protein loss through the kidneys is one of the findings that support the diagnosis.
- Joint fluid analysis — when lameness or swollen joints are part of the picture.
- Ehrlichia and Bartonella tests — infections that can give a positive ANA.
- Rheumatoid factor — another autoantibody test; neither ANA nor rheumatoid factor alone is used to diagnose a disease.
Units and conversion
Results have no unit. ANA is reported as negative or positive, usually with a titer — the highest dilution of serum, written 1:N, at which antibodies still light up the nuclei. The larger N, the more antibody: 1:160 means more antibody than 1:40. A pattern name may be added. In the app the result is stored as text.
Reference range
The reference range is on your lab’s form: the lab states from which titer it calls a result positive and how it grades titers. One veterinary diagnostic laboratory reads dog titers up to 1:40 as low and often nonspecific, and 1:80 and above as more likely to reflect SLE when the signs fit; for cats its steps are one dilution lower. Other labs may use other steps.
Cats and dogs
SLE is rare in cats. When it occurs, inflammation of the kidney filters (glomerulonephritis) is one of its major, life-threatening complications, so urine protein is watched closely. In cats a titer up to 1:20 is often nonspecific, and 1:40 or higher is more likely to reflect SLE when the clinical and laboratory findings fit. A negative result argues strongly against active SLE in cats too.
SLE in dogs is rare and can be confused with many other diseases, because its signs — fluctuating fever, shifting lameness, painful muscles, mouth ulcers, skin changes, anaemia — come and go. Low positive titers occur in older dogs and in infections, so a low titer in a dog without matching signs is often nonspecific. The staining pattern on the report does not tell which disease a dog has.
Add a lab form — Pet Tracker Space recognises the lines, keeps the form’s units and draws each indicator over time with your lab’s reference band.
Sources
- Cornell University Animal Health Diagnostic Center — ANA (anti-nuclear antibody)
- Merck Veterinary Manual — Hypersensitivity diseases in animals (systemic lupus erythematosus)
- Merck Veterinary Manual — Disorders involving immune complexes (type III reactions) in dogs
- Merck Veterinary Manual — Fever of unknown origin in animals
This page explains what a lab value means. It is not a diagnosis and not a substitute for your veterinarian — only they can interpret results for your pet.