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An ANA test is a blood test used to screen for autoimmune diseases such as systemic lupus erythematosus, or SLE. Because SLE is an autoimmune disease where the body produces antibodies against its own tissues, an ANA test is usually positive when a person has SLE; but, is it always? Is it possible to have lupus with negative ANA test results?
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What is an ANA Test?
An ANA test is a blood test that screens for anti-nuclear antibodies, or antibodies against DNA, which is the genetic material within the nucleus of every cell. This test is carried out using one of two assays, and the results are recorded as an antibody titer, which indicates the concentration of anti-nuclear antibodies in the bloodstream. People without SLE or another autoimmune disease usually have a low ANA titer, while a person with SLE will have a high one.
When an ANA test shows a high antibody titer, a special staining technique is used to visualize the antibodies under the microscope to see what pattern they form. Different ANA antibody patterns are suggestive of specific types of autoimmune disease.
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Can an ANA Test Be Negative with Lupus?
An ANA test will be positive 95 percent of the time when a person has lupus, so there are cases where a person has lupus and will have negative ANA testing. Likewise, a normal, healthy person who doesn’t have lupus or any other autoimmune disease can have a positive ANA. This is especially common in older individuals. Certain medications can also cause an ANA test to be positive as can some infections and liver diseases. A positive ANA isn’t specific for lupus, since the test can also be positive with other autoimmune diseases as well.
If an ANA test is negative, the diagnosis of SLE is less likely, but the small possibility of having the disease is still there. Depending upon a person’s symptoms, a doctor may decide to repeat the ANA test to rule out lab error or check another ANA level in the future depending upon a person’s clinical picture. Another option to check for lupus when ANA test results are negative is to check for two other antibodies that are often elevated in lupus: anti-LA and anti-RO. These are also checked by drawing blood.
Another test called an ESR test looks for general inflammation in the body, which is usually elevated in people with SLE. Unfortunately, this is a very non-specific test that can be abnormal with a variety of infections, autoimmune diseases, or other conditions that cause inflammation.
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The Bottom Line?
An ANA test will be negative in a person who has lupus only five percent of the time, so if it’s negative the diagnosis is unlikely. In most cases, anti-LA and anti-RO antibody tests can be used to confirm the diagnosis in cases where ANA is negative. If not, most doctors will continue to closely follow a patient with a negative ANA and symptoms of lupus, and repeat the test, if necessary.
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Medscape.com. “Antinuclear Antibody-Negative, Drug-Induced Lupus: Discussion “
Lab Tests Online. “ANA”
Merck Manual. Eighteen edition. 2006.