Diagnosing Lupus

Diagnosing lupus can be difficult. It may take months or even years for doctors to piece together the symptoms to diagnose this complex disease accurately. Making a correct diagnosis of lupus requires knowledge and awareness on the part of the doctor and good communication on the part of the patient. Giving the doctor a complete, accurate medical history (for example, what health problems you have had and for how long) is critical to the process of diagnosis. This information, along with a physical examination and the results of laboratory tests, helps the doctor consider other diseases that may mimic lupus, or determine if the patient truly has the disease. Reaching a diagnosis may take time and occur gradually as new symptoms appear.

For example, the antinuclear antibody (ANA) test is commonly used to look for autoantibodies that react against components of the nucleus, or "command center," of the patient's own 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 rheumatic or immune diseases, and occasionally as a finding in normal healthy adults. 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 syphilis test or a test for anticardiolipin antibody. A positive test does not mean that a patient has syphilis; however, the presence of this antibody may increase the risk of blood clotting and can increase the risk of miscarriages 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 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.

Diagnostic Tools for Lupus

• Complete blood count
• Erythrocyte sedimentation rate (ESR)
• Urinalysis
• Blood chemistries
• Complement levels
• Antinuclear antibody test (ANA)
• Other autoantibody tests (anti-DNA, anti-Sm, anti-RNP, anti-Ro [SSA], anti- La [SSB])
• Syphilis test or anticardiolipin antibody