A blood sample taken from a vein in your arm
This test measures the amount of antibody to double-stranded deoxyribonucleic acid (anti-dsDNA) that may be present in the blood. Anti-dsDNA is an autoantibody, produced when a person's immune system fails to distinguish between "self" and "non-self" cellular components. It mistakenly targets and attacks the body's own genetic material, causing inflammation, tissue damage, and other signs and symptoms that are associated with an autoimmune disorder.
Anti-dsDNA is one of several antinuclear antibodies (ANA), a group of antibodies directed against substances found in the nucleus of cells. While it may be present at a low level with a number of disorders, anti-dsDNA is primarily associated with the autoimmune disorder systemic lupus erythematosus (SLE or Lupus). SLE can affect the kidneys, joints, blood vessels, skin, heart, lungs, and the brain. Symptoms may include joint pain, rashes, fatigue, and kidney dysfunction. SLE occurs most frequently in women between the ages of 15 to 40 and is more common in non-Caucasians. While no direct cause is known, there may be some genetic predisposition. Certain drugs, chemicals, sunlight, or viral infections may trigger an episode.
One particularly serious complication of SLE is lupus nephritis, a condition characterised by inflammation of the kidneys, which can lead to protein in the urine, high blood pressure, and kidney failure. It occurs when the autoantibodies bind to antigens and become deposited in the kidneys. In the evaluation of someone with lupus nephritis, a high titre of anti-dsDNA is generally associated with ongoing inflammation and damage to the kidneys.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
How is it used?
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.
When is it requested?
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)
- 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.
What does the test result mean?
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.
Is there anything else I should know?
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.
Why might it take a long time to be diagnosed with SLE?
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.
If I have been diagnosed with SLE, will it ever go away?
Will my anti-dsDNA ever go away?
Is there anything I can do to affect my anti-dsDNA level?
Can the anti-dsDNA test be performed in my doctors surgery?
Should everyone have an anti-dsDNA test done?