The test is used to help diagnose systemic lupus erythematosus (SLE) and drug-induced lupus, but may also be positive in cases of scleroderma, Sjögren’s syndrome, Raynaud’s disease, juvenile chronic arthritis, rheumatoid arthritis, antiphospholipid antibody syndrome, autoimmune hepatitis, and many other autoimmune and non-autoimmune diseases. For this reason, SLE, which is commonly known as lupus, can be tricky to diagnose correctly. Because the ANA test result may be positive in a number of these other diseases, additional testing can help to establish a diagnosis of SLE. Your doctor may run other tests that are considered subsets of the general ANA test and that are used in conjunction with patient symptoms and clinical history to rule out a diagnosis of other autoimmune diseases.

Because autoimmune diseases can be difficult to diagnose, this test offers a reliable first step for identifying SLE and some other autoimmune disorders with a wide variety of symptoms. These symptoms, including painful or swollen joints, unexplained fever, extreme fatigue, and a red rash, may come and go over time and may be mild or severe. It may take months or years for these symptoms to show a pattern that might suggest SLE or any of the other autoimmune diseases.

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 (a low number of blood platelets), 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.

PLEASE NOTE: Numerically reported test results are interpreted according to the test's reference range, which may vary by the patient's age, sex, as well as the instrumentation or kit used to perform the test. A specific result within the reference (normal) range – for any test – does not ensure health just as a result outside the reference range may not indicate disease. To learn more about reference ranges, please see the article, Reference Ranges and What They Mean. To learn the reference range for your test, consult your doctor or laboratorian. Lab Tests Online recommends you consult your physician to discuss your test results as a part of a complete medical examination.

More specific subsets of the general ANA test are used to help pinpoint the specific autoimmune disease; these autoantibody tests include anti-dsDNA, anti-Sm, Sjögren’s syndrome antigen (SSA, SSB), Scl-70 antibodies, anti-centromere, anti-histone, and anti-RN.

Some drugs and infections as well as other conditions mentioned above can give a false positive result for the ANA test. These drugs may bring on a condition that includes SLE symptoms, called drug-induced lupus. When the drugs are stopped, the symptoms usually go away. Although many medications have been reported to cause drug-induced lupus, those most closely associated with this syndrome include hydralazine, isoniazid, procainamide, and several anticonvulsants.