Lupus is chronic and complex and is often difficult to diagnose.
There is no single laboratory test that can determine if a person has lupus.
To complicate matters, many symptoms of lupus are similar to those of other diseases, and can come and go over weeks and months. It can often take years for a diagnosis to be made.
To diagnose lupus, a doctor should be able to find physical or laboratory evidence of the condition, such as swelling of joints, protein in the urine, fluid around the lungs or heart, or a skin biopsy (test of a sample) that shows evidence of the disease. The doctor also will look at a person’s medical history and special tests to rule out other diseases.
The term “lupus” usually refers to “systemic lupus erythematosus” (SLE), but there are in fact other types of lupus–this is only one type of lupus. Other types of lupus are cutaneous or “skin” lupus erythematosus, which mainly affects the skin—not the rest of the body.
Unlike systemic lupus, cutaneous lupus does not threaten the health of other organs and tissues in the body. And although it’s clearly a concern, it’s not that common for cutaneous lupus to turn into systemic lupus. A type of cutaneous lupus called “discoid” lupus involves potentially scarring sores with inflammation, typically on the face, scalp, and ears.
“Drug-induced lupus” is triggered by the use of certain medicines. It usually goes away once the triggering medicines are stopped. Symptoms of this form of lupus are often relatively mild.
Doctors use the American College of Rheumatology’s “Eleven Criteria of Lupus” to help make—or exclude—a diagnosis of lupus.
Typically, four or more of the following criteria must be present to make a diagnosis of systemic lupus.
A positive antinuclear antibody (ANA) test does not automatically mean you have lupus. Your immune system is your body’s natural defense against disease. A positive ANA blood test shows that your immune system is making an antibody (protein) that reacts with components of your body’s cells. This is called autoimmunity and may or may not be harmful to your body. So while a positive ANA may be associated with an autoimmune illness like lupus, it does not mean you have the disease. Approximately 20% of the general population will have a positive ANA test; positive tests are also seen in other conditions, such as thyroid disease, certain liver conditions, and other autoimmune diseases.