Anti-Double Stranded DNA (Anti-dsDNA)
The anti-dsDNA (anti-double stranded DNA) antibody test is a blood test that looks for antibodies to double stranded DNA.
The anti-dsDNA antibody test is a very specific test for Systemic Lupus Erythematosus (SLE) because Anti-dsDNA antibodies aren't found in any other autoimmune disorders.
A strongly positive anti-dsDNA antibody test makes it very likely that a person has SLE.
If this test is negative, it does not necessarily rule out SLE. About 30-50% of people with SLE have a negative anti-dsDNA antibody test.
Science Behind this Test
Anti-dsDNA antibodies are a type of autoantibody. This means that they are an antibody produced by the immune system and that they target something that the body's own tissues are made of.
Anti-dsDNA attacks DNA (deoxyribonucleic acid), the basic building block that makes up our chromosomes. Our chromosomes contain our genes and encode the instructions to make all of the proteins that are essential for body functions.
Why the anti-dsDNA Test is Done
The anti-dsDNA test is usually done after another test called an ANA (anti-nuclear antibody) test. The ANA test is a screening test for autoimmune diseases but it is not specific to SLE. When the ANA test is positive and SLE is suspected, an anti-dsDNA test is ordered to help confirm the diagnosis.
Anti-dsDNA Test Results
The anti-dsDNA test's results are important to consider because:
- It helps establish a diagnosis of SLE
- It can be used to monitor disease activity in a person with SLE since the levels of anti-dsDNA antibodies can fluctuate
- If the anti-dsDNA levels are high, the disease may be active or there is a current or imminent disease flare
- If the anti-dsDNA levels are low, the disease may be "quiet" or less active