Lupus
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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. Lupus is often mistaken for other diseases. 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 as new symptoms appear.
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, or "command center," 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 (Systemic Lupus Erythematosus).
Diagnostic Tools for Lupus:
If you have symptoms, tell your doctor right away. No single test can tell if a person has lupus. But your doctor can find out if you have lupus in other ways, including:
- Medical History
Telling your doctor about your symptoms and other problems you have had can help him or her understand your situation. Keep track of your symptoms by writing them down. - Family History of Lupus or Other Autoimmune Diseases
Tell your doctor if lupus or other autoimmune diseases run in your family. - Complete Physical Examination
Your doctor will look for rashes and other signs that something is wrong. - Laboratory tests:
- Complete blood count (CBC)
- Erythrocyte sedimentation rate (ESR)
- Urinalysis (urine tests)
- Blood chemistries
- Complement levels
- Antinuclear antibody (ANA) test - the antinuclear antibody (ANA) test can show if your immune system is more likely to produce the autoantibodies of lupus. Most people with lupus test positive for ANA. But, a positive ANA does not mean you have lupus. About 2 in 10 healthy people test positive for ANA. Positive tests also are seen in other conditions, such as thyroid disease, malaria, and other autoimmune diseases. That's why your doctor will use many tools - and maybe other tests - to tell if you have lupus.
- Other autoantibody tests - anti-DNA, anti-Sm, anti-RNP, anti-Ro (SSA), anti-La (SSB)
- Anticardiolipin antibody test
- Skin Biopsy or Kidney Biopsy
With a biopsy, doctors perform a minor surgery to remove a sample of tissue. The tissue is then looked at under a microscope. Skin and kidney tissue looked at in this way can show signs of an autoimmune disease.
Together, this information can provide clues to your disease. It also can help your doctor rule out other diseases that can be confused with lupus.
References:
1) The National Women's Health Information Center - U.S. Department of Health and Human Services - Office on Women's Health - May 2008 - www.4woman.gov
2) National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) - Information Clearinghouse - National Institutes of Health - Department of Health and Human Services - NIH Publication No. 03-4178 - September 1997 - Revised August 2003 - www.niams.nih.gov
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