- ANA stands for “Antinuclear Antibody“.
- Antibodies are proteins produced by white blood cells, which normally circulate in the blood to defend against foreign invaders, such as bacteria, viruses, and toxins.
- The antibodies that target “normal” proteins within the nucleus of a cell are called antinuclear antibodies (ANA).
- Most people have antinuclear antibodies, but typically in small amounts. The presence of large amount of autoantibodies or ANAs can indicate an autoimmune disease.
- A negative ANA reading means no antinuclear antibodies are present in the body.
- A positive ANA reading alone does not indicate an autoimmune disease.
The ANA titer is a measure of the amount of ANA in the blood; the higher the titer, the more autoantibodies are present in the sample.
Patient samples are often screened for antinuclear antibodies after being diluted 1:40 and 1:160 in a buffered solution. If staining is observed at both the 1:40 and 1:160 dilutions, then the laboratory continues to dilute the sample until staining can no longer be seen under the microscope. The level to which a patient’s sample can be diluted and still produce recognizable staining is known as the ANA “titer.”
Here is an example:
1:160 positive (titer reported as 1:160)
— A negative ANA titer result suggests that ANA-associated autoimmune diseases are not present, but does not rule out the possibility. People with negative results on the ANA titer usually also have negative results for specific ANA antibodies.
— A low ANA titer (1:40 to 1:80) may be associated with preclinical disease or lack of disease.
Patients with the following systemic autoimmune diseases may have a positive test for antinuclear antibodies (ANA):
- Systemic lupus erythematosus (SLE)
- Sjögren’s syndrome
- Mixed connective tissue disease
- Drug-induced lupus
- Rheumatoid arthritis
- Oligoarticular juvenile chronic arthritis
- Polyarteritis nodosum
Patients with organ-specific autoimmune diseases may also have a positive test for ANA.
These diseases include:
- Thyroid diseases (Hashimoto thyroiditis, Grave disease)
- Gastrointestinal diseases (autoimmune hepatitis, primary biliary cholangitis [also known as primary biliary cirrhosis], inflammatory bowel disease)
- Pulmonary diseases (idiopathic pulmonary fibrosis)
Patients with infectious diseases may also test positive for ANA.
These diseases include:
- Viral infections (hepatitis C, parvovirus)
- Bacterial infections (tuberculosis)
- Parasitic infections (schistosomiasis)
Other associations with positive ANA tests have been noted, including:
- Various forms of cancer (rarely)
- As a harbinger of the future development of autoimmune disease
- Various medications, without causing an autoimmune disease
- Having one or more relatives with an autoimmune disease
Some individuals, even those without a relative with autoimmune disease, may have a positive test for ANA and yet never develop any autoimmune disease.
Additional note: A positive test for antinuclear antibodies (ANA) does not, by itself, indicate the presence of an autoimmune disease. Many normal individuals will have a positive test at low titers. Even when detected at high titer, a positive ANA result, by itself (in the absence of symptoms or physical findings), does not indicate that a patient either has, or will develop, an autoimmune disease. Some ANA appear to be unrelated to the development of autoimmune disorders. Future studies may help identify these “benign” autoantibodies and may permit health care providers to provide reassurance to their patients.
Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you.
The information on healthmatters.io is NOT intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice.