What is ANA?
ANA stands for anti-nuclear antibody. Put simply this test is looking for a protein in your blood that destroys the nuclei of your cells. There are also various sub-types of this test such as Anti-dsDNA, Anti-Ro, Anti-Sm, and others. These are discussed on other pages that can be found on the Lupus Lab Tests page.
Why it is done?
This test is currently the most sensitive test used for diagnosing SLE. 97% of people with SLE will have a positive ANA. This test can also be helpful in diagnosing Drug-induced Lupus. A positive ANA however does NOT confirm a Lupus diagnosis on it's own. At least 3 others of the 11 criteria established by the American College of Rheumatology must be present as well as a positive ANA to confirm a Lupus diagnosis. More about other possible causes of a positive ANA later in this document.
How is it done?
Laboratories take a small sample of blood, usually from the arm. The results are expressed with both a titer and a pattern. The titer is a ratio that expresses the number of times the technician had to dilute the plasma from the blood before the antibodies could no longer be detected. There are different patterns of a positive ANA; rim (sometimes called peripheral), homogenous (sometimes called smooth), speckled, diffuse, nucleolar, and centromere.
Normal Levels: (normal values may vary from lab to lab)
Titers of 1:20 or 1:40 or less are generally considered normal depending on the lab and methods used to conduct the test.
What a negative ANA means:
A negative ANA argues pretty strongly against Lupus but it does not completely rule it out. Infrequent cases of SLE patients with negative ANAs can be found when positive Anti-Ro (SSA) or antiphospholipid antibodies are present.
What a positive ANA means:
A positive ANA does not automatically mean Lupus, once again other clinical findings must be taken into account. The reason for this is because a positive ANA can also be found in many other autoimmune diseases such as Multiple Sclerosis, Autoimmune Thyroiditis, Scleroderma, Sjogren's Syndrome, Autoimmune Hepatitis, and Rheumatoid Arthritis. This test can also be positive in people with some infectious diseases like mononucleosis, chronic hepatitis, malaria and lepromatous leprosy. There are certain drugs such as isoniazid, procainamide, chlorpromazine, and hydralazine can cause a positive ANA also. 30-40% of first degree relatives of SLE patients will have a positive ANA and no symptoms. Finally, as many as 20% of completely healthy individuals will also have a positive ANA.
What the titer number means:
As stated before the titer is a ratio that expresses the number of times the technician had to dilute the plasma from the blood before the antibodies could no longer be detected. In other words, a titer of 1:40 would mean that the antibodies were last detected when 1 part of the blood was diluted with 40 parts of either water or saline. The higher the second number the higher the concentration of antibodies. Since the amount of dilution fluid is doubled the titers can increase rapidly from 1:40 to 1:80 to 1:160 to 1:320 to 1:640 and so on. Antibodies fluctuate in concentration during the course of disease and a high or low titer does NOT indicate the level of disease activity and can not reliably be used to determine disease activity level. However, the higher the titer, the more likely an autoimmune disease is present.
What the pattern means:
Rim / Peripheral - found almost exclusively in people with SLE
Homogenous / Smooth - found in high titers in SLE also found in Drug-Induced Lupus, and other autoimmune diseases, also the most commonly found pattern in healthy individuals
Speckled - found in SLE, mixed connective tissue disease, Sjogren's Syndrome, Scleroderma
Diffuse - non-specific pattern
Nucleolar - found in Scleroderma, CREST Syndrome, systemic sclerosis, and sometimes SLE or Rheumatoid Arthritis
Centromere - found in PSS with CREST Syndrome, polymyositis, Raynaud's Syndrome
**Note: Typically an ANA test does not test for all of the patterns. If you have a negative ANA but still suspect you have an autoimmune disease, ask your doctor if all patterns were run.