Anti Nuclear Antibody

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نعود اليكم من جديد بعد فترة غياب عن المنتدى

Also known as: Antinuclear Antibody test, fluorescent antinuclear antibody, FANA
Formally known as: Antinuclear Antibody Test
Related tests: Autoantibody tests

What is being tested?

The ANA test identifies the presence of antinuclear antibodies (ANA) in blood. Sometimes the immune system malfunctions and produces substances that attack your body's own cells and tissues instead of foreign substances. These substances, called autoantibodies, are produced by the body's immune system – the body's defense system against invasion by foreign substances such as viruses and bacteria.

When this happens, the resulting disease is termed an autoimmune disease (autoimmunity means immunity to self). The presence of ANA is a marker of an autoimmune process and is associated with several autoimmune diseases but is most commonly seen in systemic lupus erythematosus (SLE

What does the test result mean?

A positive test result may suggest an autoimmune disease, but further specific testing is required to assist in making a final diagnosis. ANA test results can be positive in people without any known autoimmune disease. While this is not common, the frequency of a false positive ANA result increases as people get older.

About 95% of SLE patients have a positive ANA test result. If a patient has symptoms of SLE, such as arthritis, a rash, and autoimmune thrombocytopenia, then s/he probably has SLE. In these cases, a positive ANA result can be useful to support SLE diagnosis.

If needed, two subset tests, anti-dsDNA and anti-SM, can help to show that the condition is SLE. If anti-dsDNA autoantibodies are found, this supports the diagnosis of SLE. Higher amounts of anti-Sm are more specific for SLE.

A positive ANA can also mean that the patient has drug-induced lupus. This condition is associated with the development of autoantibodies to histones. An anti-histone test can be given to support the diagnosis of drug-induced lupus.

Other conditions in which a positive ANA test result man be seen include:

* Sjögren’s syndrome: Between 40% and 70% of patients with this condition have a positive ANA test result. While this finding supports the diagnosis, it is not required for diagnosis. Again, your doctor may want to test for two subsets of ANA, the ribonucleoproteins SSA and SSB.

The frequency of autoantibodies to SSA in patients with Sjögren’s can be 90% or greater if the test is done by enzyme immunoassay.

* Scleroderma: About 60% to 90% of patients with scleroderma have a positive ANA finding. In patients who may have this condition, the subset tests can help distinguished two forms of the disease, limited versus diffuse. The diffuse form is more severe.

Limited disease is most closely associated with the anticentromere pattern of ANA staining (anticentromere test), while the diffuse form is associated with autoantibodies to the anti–Scl-70.

* A positive result on the ANA also may show up in patients with Raynaud’s disease, juvenile chronic arthritis, or antiphospholipid antibody syndrome, but a doctor needs to rely on clinical symptoms and history for diagnosis.

A negative ANA result makes SLE an unlikely diagnosis. Unless an error in the testing is suspected, it is not necessary to immediately repeat a negative ANA test. However, because autoimmune diseases change over time, it may be worthwhile to repeat the ANA test in the future.

Aside from rare cases, further autoantibody (subset) testing is not necessary if a patient has a negative ANA result

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