What is an antinuclear antibody?

An antibody is a protein made by white blood cells. Antibodies help defend against invaders (for example, viruses) that cause disease or infection in the body.

An antinuclear antibody (ANA) is an antibody that mistakenly binds to healthy cells normally present in the body. If there are enough ANAs present, this can be a laboratory sign that the immune system is attacking or causing harm to the body. This is known as an autoimmune disorder. Autoimmune disorders can cause inflammation (swelling) and disease, such as arthritis.

ANAs are usually found in people who have autoimmune conditions such as systemic lupus erythematosus. They may also be seen in other autoimmune diseases, such as mixed connective tissue disease, Sjogren’s syndrome, dermatomyositis, polymyositis, scleroderma, Raynaud’s disease, and juvenile idiopathic arthritis.

When should a child get an antinuclear antibody test ?

Some researchers believe that the ANA test is overused in children. Instead of using it for all children who have pain in the muscles, joints, or bones, these researchers believe that the test should be used only for children who are likely to have an autoimmune disease and who have definite symptoms (low-grade fever, joint swelling, muscle weakness, and/or unexplained rashes).

The ANA test is limited in how well it can accurately diagnose disease by itself. The ANA test has a high "false positive" rate, meaning that many people who don’t have an autoimmune disease can have elevated ANA levels. For example, many children have a positive ANA test, even though they do not have an autoimmune disease.

It has also been shown that ANAs are present not only in people who have a disease but also in those who have infections (such as viral infections) or cancer (such as acute lymphocytic leukemia). ANAs can also be found in people who are exposed to environmental toxins, and those who are taking certain drugs (such as hydralazine, isoniazid, procainamide, and some anticonvulsants).

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