Anti-DNA antibodies are antibodies found in systemic lupus erythematosus (SLE), an autoimmune disease. The immune system defends us against attacks from foreign cells and organisms, such as bacteria and viruses. But it often goes haywire and sees some of its own tissues as foreign. The production of antibodies against the body’s own tissues is the cause of a large number of autoimmune diseases that manifest as inflammation, muscle and joint pain, fatigue and often erythema (redness) of the face. Anti-DNA are antibodies directed against the DNA contained in the chromosomes of our cells.
A very low anti-DNA level is considered negative but does not rule out an SLE diagnosis (anti-DNA antibody tests are only positive in 50% to 70% of SLE cases). Anti-DNA levels greater than 9 international units per millilitre of blood (IU/mL) in the presence of suggestive symptoms and signs confirm the presence of SLE (especially if the anti-Sm test result is also positive). Results between 5 and 9 IU/mL are in a grey area and need to be reinterpreted based on other clinical data. These levels can be seen with other autoimmune diseases such as Sjögren’s (dry eye) syndrome or mixed connective tissue disease.