Testing for Lupus
Causes | Symptoms | Types | Testing | Treatment | Other Illnesses | Quality of Life
How is lupus diagnosed?
Diagnosing lupus can be difficult. There are many possible symptoms and some of them are very similar to symptoms of other diseases.
The diagnostic workup relies on a complete assessment of the patient and laboratory tests. The essential elements of the workup are:
- Complete medical history to find out current and past symptoms and look for links or causes
- Complete physical examination to assess overall health and the impact of lupus on the body
- Laboratory tests of the blood and urine
- Period of observation, possibly years, to piece together results and changes over time
What can blood tests show?
No single test can prove or disprove that an individual has lupus, but several blood tests can provide helpful clues.
- A complete blood count (CBC) can show if anemia is present. A CBC can also provide important information on white blood and platelet counts, kidney and liver function.
- A blood differential test counts the different types of white blood cells and measures the percentages of each. This shows if the white blood cells are in proper portion to each other. Reduced levels of two types of white blood cells, lymphocytes and granulocytes, make people with lupus more likely to get infections. A shortage of lymphocytes is known as lymphocytopenia or lymphopenia. A shortage of granulocytes is known as granulocytopenia.
- The erythrocyte sedimentation rate (ESR or Sed rate) indirectly measures inflammation. An increased Sed rate indicates that inflammation is present in the body, but cannot tell where or why.
- Another common test measures the blood level of a group of substances called complement. Levels of complement are often low in people with lupus, especially during flares of the disease.
- The antinuclear antibody (ANA) test looks for autoantibodies that react against components in the nucleus of a cell. Most people with lupus test positive for ANA, but so can others who don't have lupus. These include people with infections and other autoimmune diseases.
- Other blood tests look for individual types of autoantibodies. These include anti-dsDNA, anti-Sm, anti-RNP, anti-Ro/SSA and anti-La/SSB, and lupus anticoagulant. These blood tests are not perfect. Most, but not all, people with lupus test positive for these antibodies. Some people who don't have lupus can also test positive.
What other tests can provide useful information?
Important information about kidney function can come from analyzing a sample of urine (urinalysis).
A sample of skin or tissue from a kidney may be removed and examined under a microscope. Known as a biopsy, this procedure can show signs of an autoimmune disease.
X-rays and other imaging studies can show the effects of lupus on body organs. These studies also can help rule out other conditions.
Written 12/07
