Why it's done

An ANA test detects antinuclear antibodies in your blood. Your immune system normally makes antibodies to help you fight infection. In contrast, antinuclear antibodies often attack your body's own tissues — specifically targeting each cell's nucleus.

In most cases, a positive ANA test indicates that your immune system has launched a misdirected attack on your own tissue — in other words, an autoimmune reaction. But some people have positive ANA tests even when they're healthy.

Your doctor may order an ANA test if he or she suspects you have an autoimmune disease such as lupus, rheumatoid arthritis or scleroderma.

How you prepare

If your blood sample is being used only for an ANA test, you can eat and drink normally before the test. If your blood sample will be used for additional tests, you may need to fast for a certain amount of time before the test. Your doctor will give you specific instructions.

Certain drugs affect the accuracy of the test, so bring your doctor a list of all the medications you take.

What you can expect

For an ANA test, a member of your health care team takes a sample of blood by inserting a needle into a vein in your arm. The blood sample is sent to a lab for analysis. You can return to your usual activities immediately.

Results

For an ANA test, a member of your health care team takes a sample of blood by inserting a needle into a vein in your arm. The blood sample is sent to a lab for analysis. You can return to your usual activities immediately.