SS-A (or Ro), SS-B (or La)
This is a blood test for Sjögren's syndrome, an autoimmune disease that makes it hard for your glands to produce enough moisture. The condition causes discomfort by drying out mucous membranes, including the ones in the mouth, eyes, nose, lungs, and vagina. Sjögren's may also affect the joints, kidneys, and the nervous, vascular, respiratory and digestive systems.
To help diagnose the condition, doctors use this blood test to check for Sjögren's-related autoantibodies. These are substances in the blood that attack the body's tissues instead of foreign substances like bacteria.
Sjögren's is a common problem. Women account for most cases. Sjögren's often happens along with other autoimmune disorders, such as rheumatoid arthritis or lupus.
You might need this test if you have abnormal liver tests or show symptoms of Sjögren's syndrome, including:
Dry eyes or corneal ulcers
Gritty sensation in the eyes
Feeling of dryness in the mouth and difficulty swallowing dry food
Heartburn and reflux
Repeated bouts of bronchitis and pneumonia
Difficulty concentrating and "brain fog"
Numbness and tingling in the feet and toes
You may need other tests to help diagnose Sjögren's, including tests that measure eye dryness and salivary gland function. You may also have other blood tests.
Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.
A number of conditions can cause dryness of the eyes and mouth, but if you have certain antibodies in your blood, it means you may have Sjögren's. These autoantibodies include:
SS-A, also called Ro
SS-B, also called La
Antinuclear antibody, or ANA
A normal test doesn't show any antibodies to Ro or La. But people with Sjögren's don't always have these autoantibodies.
The test requires a blood sample, which is drawn through a needle from a vein in your arm.
Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.
Other conditions can cause a positive test for Ro or La, including lupus and vasculitis.
You don't need to prepare for this test. Be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.