Patient education: Antinuclear antibodies (ANA) (Beyond the Basics)

WHAT ARE ANTINUCLEAR ANTIBODIES? — A health care provider may request that a patient have a test for antinuclear antibodies (ANA) as part of an evaluation for possible autoimmune disease. Antibodies are proteins that are made as part of an immune response. Normally, the immune system responds to an infection by producing large numbers of antibodies to fight bacteria or viruses. However, when a person has an autoimmune disease, the immune system malfunctions and may produce large amounts of potentially harmful antibodies directed against one's own body. These self-directed antibodies are referred to as autoantibodies. Autoantibody-mediated inflammation and cell destruction may affect blood cells, skin, joints, kidneys, lungs, nervous system, and other organs of the body.

The ANA test identifies autoantibodies that target substances contained inside cells. Although the name implies that the test detects only autoantibodies directed against components of the nucleus, the test can also be used to detect antibodies directed against cellular components that are contained within the cell cytoplasm, outside of the nucleus.

WHY TEST FOR ANTINUCLEAR ANTIBODIES? — Autoimmune diseases may be very difficult to diagnose because symptoms often vary from patient to patient. The results of the antinuclear antibody (ANA) test, together with a health care provider's careful consideration of a patient's symptoms, physical findings, and other laboratory test results, may assist in the diagnosis of autoimmune disorders.

●A positive test for ANA may help determine the specific type of autoimmune disease that is affecting a patient.

●A negative test for ANA can assist health care providers by decreasing the likelihood that a patient’s symptoms are caused by an autoimmune disease.

HOW IS AN ANTINCULEAR ANTIBODY TEST DONE? — In general, there are two ways to test for antinuclear antibodies (ANA). The results depend on which type of test was done.

●Indirect immunofluorescence – One type of ANA test uses indirect immunofluorescence and gives two types of results: a titer (a measure of how much ANA is in the blood) and a pattern (where the ANA was detected in the cells). In this test, antinuclear (or anti-cytoplasmic) antibodies bind to cells that have been fixed and permeabilized on a slide. The addition of a secondary antibody (with an attached fluorescent dye) directed against human antibodies may reveal staining of the nucleus or cytoplasm as detected using a fluorescence microscope. Patient samples are often screened for ANA 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.” 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.

It is difficult to standardize the ANA test between laboratories. One approach has been to modify the test reagents such that 30 percent of normal individuals will have a positive test when their sample is tested at a dilution of 1:40. This standardization makes the ANA test very sensitive for the diagnosis of autoimmune diseases but results in many false-positive results. At a dilution of 1:160, only 5 percent of normal individuals have a positive test for ANA. The 1:160 dilution increases the specificity of the ANA test for the diagnosis of autoimmune diseases.

●Solid-phase assays – The other type of ANA test uses solid-phase assays. In this test, a panel of autoantigens is attached to a solid surface. Next, the patient sample and a secondary antibody directed against human antibodies (with an attached fluorescent dye or an enzyme that catalyzes a colorimetric reaction) are added. The results may be reported as being within a “positive,” “indeterminate,” or “negative” range for each specific autoantibody.

WHAT DOES A POSITIVE ANTINUCLEAR ANTIBODY TEST MEAN? — Patients with the following systemic autoimmune diseases may have a positive test for antinuclear antibodies (ANA):

●Systemic lupus erythematosus (SLE) (see "Patient education: Systemic lupus erythematosus (Beyond the Basics)")

●Scleroderma

●Sjögren’s disease (see "Patient education: Sjögren's disease (Beyond the Basics)")

●Mixed connective tissue disease

●Drug-induced lupus

●Polymyositis/dermatomyositis (see "Patient education: Polymyositis, dermatomyositis, and other forms of idiopathic inflammatory myopathy (Beyond the Basics)")

●Rheumatoid arthritis (see "Patient education: Rheumatoid arthritis symptoms and diagnosis (Beyond the Basics)")

●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) (see "Patient education: Hyperthyroidism (overactive thyroid) (Beyond the Basics)" and "Patient education: Hypothyroidism (underactive thyroid) (Beyond the Basics)")

●Gastrointestinal diseases (autoimmune hepatitis, primary biliary cholangitis [also known as primary biliary cirrhosis], inflammatory bowel disease) (see "Patient education: Autoimmune hepatitis (Beyond the Basics)" and "Patient education: Ulcerative colitis (Beyond the Basics)" and "Patient education: Crohn disease (Beyond the Basics)")

●Pulmonary diseases (idiopathic pulmonary fibrosis)

Patients with viral infections may also test positive for ANA. These diseases include Epstein-Barr virus, parvovirus B19, and hepatitis C.

Other associations with positive ANA tests have been noted, including:

●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

●Various forms of cancer (rarely)

Some individuals may have a positive test for ANA and yet never develop any autoimmune disease.

A WORD OF CAUTION — A positive test for antinuclear antibodies (ANA) does not, by itself, indicate the presence of an autoimmune disease. As mentioned above, because of the design of the ANA test, 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.

WHAT FOLLOW-UP TESTING MIGHT BE DONE? — If a patient has a positive test for antinuclear antibodies (ANA), their health care provider, depending on the patient's symptoms or findings on physical examination, may order additional tests to identify specific types of autoantibodies. Some examples are provided below:

Systemic lupus erythematosus — If a diagnosis of SLE is suspected, then additional tests, looking for autoantibodies directed against double-stranded DNA, Sm antigens, and ribosomal P antigens may be ordered. Because these antibodies are relatively specific for SLE, the results may provide important clues to facilitate the diagnosis of SLE. (See "Patient education: Systemic lupus erythematosus (Beyond the Basics)".)

Sjögren's disease — If a diagnosis of Sjögren's disease is suspected, the health care provider may test for autoantibodies directed against antigens known as Ro/SSA and La/SSB. The presence of these autoantibodies provides support for the diagnosis of Sjögren's disease, a disorder which involves autoimmune destruction of the glands that produce tears and saliva.

Drug-induced systemic lupus erythematosus — If a diagnosis of drug-induced SLE is suspected, then a test for antihistone antibodies may be ordered. Antihistone antibodies are nearly always present in patients with drug-induced SLE. If antihistone antibodies are not detected, then the likelihood of this diagnosis (drug-induced SLE) is reduced.

WHERE TO GET MORE INFORMATION — Your health care provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

This topic currently has no corresponding Basic content.

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Systemic lupus erythematosus (Beyond the Basics)
Patient education: Polymyositis, dermatomyositis, and other forms of idiopathic inflammatory myopathy (Beyond the Basics)
Patient education: Rheumatoid arthritis symptoms and diagnosis (Beyond the Basics)
Patient education: Sjögren's disease (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Antibodies to double-stranded (ds)DNA, Sm, and U1 RNP
Antiribosomal P protein antibodies
Clinical manifestations and diagnosis of systemic lupus erythematosus in adults
Investigational biologic markers in the diagnosis and assessment of rheumatoid arthritis
Measurement and clinical significance of antinuclear antibodies
Drug-induced lupus
The anti-Ro/SSA and anti-La/SSB antigen-antibody systems

The following organizations also provide reliable health information.

●Arthritis Foundation

(www.arthritis.org)

●Lupus Foundation of America, Inc

(www.lupus.org)

●National Institute of Arthritis and Musculoskeletal and Skin Diseases

(www.niams.nih.gov)

●National Library of Medicine

(www.medlineplus.gov/ency/article/003535.htm)

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