A positive antinuclear antibodies, or ANA, test result can change to negative, especially in people who have short-term viral infections, according to the American College of Rheumatology. However, even a positive ANA test does not mean that the person tested has an autoimmune disease.
Most people have small amounts of antinuclear antibodies in their bodies, and the percentage of healthy people who still test positive after an ANA test is between 3 and 15 percent, explains the American College of Rheumatology. The percentage goes up as the cohort ages, and positive results occur for between 10 and 37 percent of people over 65. Women over 65 are especially likely to have false positive ANA tests, notes Mayo Clinic. People with cancer can also have positive ANA tests.
A person can have a positive ANA test if he is on certain medications, such as blood pressure and anti-seizure drugs, reports Mayo Clinic. Stopping these medications is another reason why a positive ANA test can convert to a negative. It is important that a patient lets his doctor know what drugs he takes before the ANA test, explains the American College of Rheumatology.
Because so many otherwise healthy people test positive for ANAs, the doctor conducts follow-up tests to make sure his patient does not suffer from autoimmune diseases such as rheumatoid arthritis or lupus, notes the American College of Rheumatology.