Anti-dsDNA

The anti-dsDNA test is used in support of a diagnosis of systemic lupus erythematosus (SLE) and distinguishes it from other autoimmune disorders. The test is typically requested following a positive ANA test in people who have clinical signs that suggest SLE. It may be requested along with another autoantibody associated with SLE, the anti-Sm (Smith antibody) test, which is often performed as part of an extractable nuclear antigen (ENA) panel. Depending upon clinical signs and the doctor's suspicions, additional autoantibodies may be requested to help distinguish between, and rule out, other autoimmune disorders.

The anti-dsDNA test may be used to monitor disease activity in a person who has been diagnosed with SLE. Those with SLE often have flare-ups where symptoms worsen and then die down. Increased anti-dsDNA levels may be seen prior to and during these flare-ups.

An anti-dsDNA test is requested when a person shows signs and symptoms that could be due to SLE AND has had a positive ANA test, especially when the ANA presents as a "homogeneous" or "speckled" fluorescent pattern. (See the article on ANA for more on this.) SLE is strongly associated with a positive ANA, which is seen in about 95% of SLE cases. However, a positive ANA is seen in many other conditions whereas a positive anti-dsDNA is fairly specific for SLE. Since anti-dsDNA is more specific for ANA, the test will not usually be requested when the ANA is negative.

Some signs and symptoms of SLE include:

• Muscle pain
• Arthritis-like pain in one or more joints (but no or little joint damage)
• Red rash that frequently resembles a butterfly across the nose and cheek areas (malar rash)
• Fever
• Persistent fatigue
• Sensitivity to ultraviolet light
• Hair and weight loss
• Inflammation and damage to organs and tissues, including the kidneys, lungs, heart, lining of the heart, central nervous system, and blood vessels

The anti-dsDNA test may be requested periodically to monitor disease progression or flare-ups in a person who has been diagnosed with SLE. It may be repeated when an initial test result is negative but clinical signs and symptoms persist.

The results of an anti-dsDNA test are usually considered together with a person's medical history, signs and symptoms, and results of other autoantibody tests.

A high level of anti-dsDNA is strongly associated with SLE and is often significantly increased during or just prior to an SLE flare-up. If the anti-dsDNA is positive and the person tested has other clinical signs associated with SLE, then there is a strong possibility that this is due to SLE.. This is especially true if an anti-Sm test is also positive.

A very low level of anti-dsDNA is considered negative but does not exclude a diagnosis of SLE. Only about 50-60% of those with SLE will have anti-dsDNA. Low to moderate levels of the autoantibody may be seen with other autoimmune disorders, such as Sjögren syndrome and mixed connective tissue disease (MCTD).

Anti-dsDNA tests are semi-quantitative and may be performed using different assays. Many laboratories use an anti-dsDNA ELISA test (enzyme-linked immunoabsorbent assay), a very reliable and sensitive test.

Anti-dsDNA is sometimes present with diseases such as chronic hepatitis, primary biliary cirrhosis, and infectious mononucleosis. It may also be seen in those taking drugs such as procainamide and hydralazine. It is not usually requested under these conditions.

In addition to testing for anti-double-stranded DNA, there is also an anti-single-stranded DNA test. This autoantibody is less commonly tested and is not strongly associated with SLE but may be seen with other autoimmune disorders.

A doctor must rely not only test results, but on clinical symptoms and the person's history for diagnosis. Symptoms may be nonspecific and often come and go. Test results may not initially be positive for these autoantibodies due to the cyclic nature of autoimmune disorders. In some cases, it may take months or years to show a pattern that might suggest SLE or any of the other autoimmune diseases.