bone, joint, and muscle disorders
Systemic Lupus Erythematosus (SLE)
Diagnosis of Lupus
A doctor's examination Laboratory tests Doctors suspect lupus mainly on the basis of the person’s symptoms during a thorough physical examination, particularly in a young woman. To help confirm the diagnosis, doctors do several laboratory tests. Although there is no single laboratory test that confirms the diagnosis of lupus, doctors do these tests to rule out other connective tissue disorders. Doctors then base the diagnosis of lupus on all of the information they gather, including symptoms, physical examination results, and all test results. Doctors use this information to help them determine whether people meet specific, established criteria that are used to confirm lupus. Nonetheless, because of the wide range of symptoms, distinguishing lupus from similar diseases and making the diagnosis can be difficult. Although blood test results can help doctors diagnose lupus, they alone cannot confirm a definite diagnosis of lupus because sometimes the abnormalities they detect are present in healthy people or in people who have other disorders. A blood test can detect antinuclear antibodies (ANA), which are present in almost all people who have lupus. However, these antibodies also occur in other diseases. Therefore, if antinuclear antibodies are detected, a test for antibodies to double-stranded DNA as well as a test for other autoimmune antibodies (autoantibodies) are done. A high level of these antibodies to DNA strongly supports the diagnosis of lupus, but not all people who have lupus have these antibodies. Other blood tests, such as measuring the level of complement proteins (proteins with various immune functions, such as killing bacteria), are also done and can help predict the activity and course of the disease in some people. Women with lupus who have repeated miscarriages or have had problems with blood clots should be tested for antiphospholipid antibodies. This is an important test when planning contraceptive methods or pregnancy. This blood test, which detects antibodies to phospholipids, can also help identify people at risk of repeated blood clots. Women with positive antibodies to phospholipids should not take estrogen-containing oral contraceptives and should choose other methods of contraception. Blood tests can also indicate a low red blood cell count ( Overview of Anemia ), a low white blood cell count, or a low platelet count. People who have anemia undergo a direct Coombs test. This test is used to detect increased amounts of certain antibodies that are attached to the surface of red blood cells and can destroy red blood cells, causing anemia. Additional laboratory tests are done to detect the presence of protein or red blood cells in the urine ( Urinalysis and Urine Culture ) or an elevation of creatinine in the blood. These findings indicate kidney inflammation of the filtering structure in the kidneys (glomeruli), a condition referred to as 