Antibodies to double-stranded DNA (anti-dsDNA) are antibodies that attack the DNA -- the genetic material -- inside the cell nucleus. Anti-dsDNA antibodies are found in half of the people with lupus, but lupus can still be present even if these antibodies are not detected.
Basically this just means that these antibodies are found in about 50% of Lupus patients and their sole job is to attack their own DNA. You can still have Lupus and not have the Anti DS-DNA antibody. There may be false negatives in this test but very seldom is there a false positive.