Lupus is a disease of the immune system that happens when the body attacks its own tissues and organs. There are several blood tests for lupus, such as a blood cell count, a erythrocyte sedimentation rate test, a test for syphilis or an antinuclear antibody (ANA) test. Typically, a complete blood count (CBC) test is the first test ordered.
In a complete blood count test, a laboratory technician counts the number of blood cells in a sample. The technician measures the number of red blood cells, white blood cells and hemoglobin, a protein in red blood cells. If the red blood cell number is low, it could indicate anemia, which is a common lupus symptom.
If the complete blood count result is low, a doctor usually will order other blood tests for lupus. A erythrocyte sedimentation rate test can reveal inflammation in the body. In this test, a technician measures how long it takes for blood cells to settle at the bottom of a test tube. A faster-than-normal rate can indicate any of several diseases, including lupus.
Lupus often will cause a syphilis test to return a false positive. This is caused by the presence of anti-phospholipid antibodies in the blood. These anti-phospholipid antibodies are a sign of lupus, and they can increase the risk of severe complications, such as blood clots and strokes.
An antinuclear antibody test, another one of the blood tests for lupus, looks for antibodies, which are produced by the immune system. If they are present, then the immune system has been active, which can be a symptom of lupus. These antibodies also can be present as a result of an infection or certain medications, so a positive result on this test could indicate lupus, or it could be caused by other factors.
Clotting tests are among the other types of blood tests for lupus. A clotting test measures how fast the blood clots at the site of a wound. A doctor also might order lupus urine tests, which measure kidney functioning. Lupus can damage the kidneys without causing any symptoms, so it is important for their condition to be checked.
There are a number of blood tests for lupus because it is a difficult disease to diagnose. Lupus develops slowly, so it can be difficult to put together all of the symptoms that appear over a long period of time. There is no single definitive blood test for lupus, and many of the lupus blood tests can indicate other conditions as well.
