ANA test detects antinuclear antibodies (ANA) 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.
Positive ANA tests, in most of the cases indicate 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.
Why It's Done
Many rheumatic diseases have similar signs and symptoms — joint pain, fatigue and fever. While an ANA test can't confirm a specific diagnosis, it can rule out some diseases. And if the ANA test is positive, your blood can be tested for the presence of particular antinuclear antibodies, some of which are specific to certain diseases.
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 an amount of time before the test. Your doctor will give you instructions.
Certain drugs affect the accuracy of the test, so bring your doctor a list of 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.
The presence of antinuclear antibodies is a positive test result. But having a positive result doesn't mean you have a disease. Many people with no disease have positive ANA tests — particularly women older than 65.
Mononucleosis and other chronic infectious diseases have been associated with the development of antinuclear antibodies. Some blood pressure lowering drugs and certain anti-seizure medications may trigger antinuclear antibody formation, as well.
If your doctor suspects you have an autoimmune disease, he or she is likely to order a number of tests. The result of your ANA test is one piece of information your doctor can use to help determine the cause of your signs and symptoms.
A rheumatoid factor test measures the amount of rheumatoid factor in your blood. Rheumatoid factors are proteins produced by your immune system that can attack healthy tissue in your body.
High levels of rheumatoid factor in the blood are most often associated with autoimmune diseases, such as rheumatoid arthritis and Sjogren's syndrome. But rheumatoid factor may be detected in some healthy people, and people with autoimmune diseases sometimes have normal levels of rheumatoid factor.
Reasons behind this test
A rheumatoid factor test is one of a group of blood tests primarily used to help pinpoint a diagnosis of rheumatoid arthritis. These other tests may include:
- Anti-nuclear antibody (ANA)
- Anti-cyclic citrullinated peptide (anti-CCP) antibodies
- C-reactive protein (CRP)
- Erythrocyte sedimentation rate (ESR, or sed rate)
The amount of rheumatoid factor in your blood may also help your doctor choose the treatment approach that will work best for your situation.
During a rheumatoid factor test, a small sample of blood is drawn from a vein in your arm. This typically takes just a few minutes. Your blood sample is sent to a laboratory for testing.
A positive rheumatoid factor test result indicates that a high level of rheumatoid factor was detected in your blood. A higher level of rheumatoid factor in your blood is closely associated with autoimmune disease, particularly rheumatoid arthritis. But a number of other diseases and conditions can raise rheumatoid factor levels, including:
- Chronic infections
- Inflammatory lung diseases, such as sarcoidosis
- Mixed connective tissue disease
- Sjogren's syndrome
- Systemic lupus erythematosus
Some healthy people have positive rheumatoid factor tests, though it's not clear why. And some people who have rheumatoid arthritis will have low levels of rheumatoid factor in their blood.