No single test can determine whether a person has lupus, but several laboratory tests may help the doctor to make a diagnosis. The most useful tests identify certain autoantibodies often present in the blood of people with lupus. For example, the antinuclear antibody (ANA) test is commonly used to look for autoantibodies that react against components of the nucleus of the body's cells. Most people with lupus test positive for ANA; however, there are a number of other causes of a positive ANA besides lupus, including infections, other autoimmune diseases, and occasionally as a finding in healthy people. The ANA test simply provides another clue for the doctor to consider in making a diagnosis. In addition, there are blood tests for individual types of autoantibodies that are more specific to people with lupus, although not all people with lupus test positive for these and not all people with these antibodies have lupus. These antibodies include anti-DNA, anti-Sm, anti-RNP, anti-Ro (SSA), and anti-La (SSB). The doctor may use these antibody tests to help make a diagnosis of lupus.
Some tests are used less frequently but may be helpful if the cause of a person's symptoms remains unclear. The doctor may order a biopsy of the skin or kidneys if those body systems are affected. Some doctors may order a test for anticardiolipin (or antiphospholipid) antibody. The presence of this antibody may indicate increased risk for blood clotting and increased risk for miscarriage in pregnant women with lupus. Again, all these tests merely serve as tools to give the doctor clues and information in making a diagnosis. The doctor will look at the entire picture-medical history, symptoms, and test results-to determine if a person has lupus.
Other laboratory tests are used to monitor the progress of the disease once it has been diagnosed. A complete blood count, urinalysis, blood chemistries, and the erythrocyte sedimentation rate (ESR) test can provide valuable information. Another common test measures the blood level of a group of substances called complement. People with lupus often have increased ESRs and low complement levels, especially during flares of the disease. X rays and other imaging tests can help doctors see the organs affected by SLE.
Diagnostic Tools for Lupus
- Medical history
- Complete physical examination
- Laboratory tests:
- Complete blood count (CBC)
- Erythrocyte sedimentation rate (ESR)
- Blood chemistries
- Complement levels
- Antinuclear antibody test (ANA)
- Other autoantibody tests such as anti-DNA, anti-Sm, anti-RNP, anti-Ro (SSA), anti-La (SSB)
- Anticardiolipin antibody test
- Skin biopsy
- Kidney biopsy
Diagnosing and treating lupus are often a team effort between the patient and several types of health care professionals. A person with lupus can go to his or her family doctor or internist, or can visit a rheumatologist. A rheumatologist is a doctor who specializes in rheumatic diseases (arthritis and other inflammatory disorders, often involving the immune system).
Clinical immunologists (doctors specializing in immune system disorders) may also treat people with lupus. As treatment progresses, other professionals often help. These may include nurses, psychologists, social workers, nephrologists (doctors who treat kidney disease), hematologists (doctors specializing in blood disorders), dermatologists (doctors who treat skin disease), and neurologists (doctors specializing in disorders of the nervous system).