Many autoimmune disorders are diagnosed based on symptoms, a physical exam, and the results of blood tests. These diseases can be difficult to diagnose, especially early on. Sometimes the symptoms of one disease overlap with those of another. In these cases, an overlap or "mixed" disease may be present.
Some autoimmune disorders need other tests to make the diagnosis. A biopsy sample, or small piece of tissue, can be removed from an affected area. This tissue can then be tested and examined in the lab. A biopsy sample can be taken from almost any part of the body, including the skin, kidney, liver, or intestines.
Special X-ray tests may need to be done. For example, changes in the joints seen on joint X-rays can help make the diagnosis of rheumatoid arthritis in some cases.