An autoimmune disorder, systemic lupus erythematosus, may affect any part of the body. This disorder can be mild and patient’s may live a relatively normal life or it may be severe enough to cause death. There are a number of diagnostic tests that may be used to aid in making a lupus diagnosis. A western blot test for lupus is a blood test doctors may use during the diagnostic process.
Why is This Test Performed?
A western blot test for lupus is used to identify proteins and is a serum electrophoretic analysis. It can be used to look for the presence of antibodies to specific antigens. It is sometimes used to confirm enzyme-linked immunosorbent assay (ELISA) results and is considered more precise than the ELISA test. This test is typically used for HIV/AIDS or Lyme disease. When used in cases of lupus, it is generally to rule out one or both of these conditions, though, some doctors may have other uses in terms of lupus.
How is This Test Performed?
Patients most often will not have to prepare for this test. This blood test requires a venous sample from the back of one of the patient’s hands or the inside of one of the elbows. Antiseptic is used to cleanse the intended puncture site and a rubber tourniquet is tightly wrapped around the upper part of the arm to force the blood to rush to the vein. A needle is then carefully inserted into a vein and enough blood is allowed to collect into an airtight vial. The rubber tourniquet is removed followed by the needle and a bandage is placed on the puncture site.
This is a basic blood test. Most patients report a mild pricking sensation when the needle is inserted. Few patients report moderate pain. There may be some throbbing following this procedure.
A negative test generally means that the patient does not have Lyme disease or HIV/AIDS. However, it does not mean an early HIV infection is not present. It also does not exclude a diagnosis of lupus.
An abnormal ELISA result could mean a positive HIV infection, but not necessarily. Syphilis, Lyme disease and lupus could also produce an abnormal result. If ELISA is abnormal, a western blot is performed to confirm it. If the western blot turns out to be negative it means that the ELISA was a false positive.
In some cases, a patient may have a hard time giving blood which can be uncomfortable for him or her. While slight, other possible blood draw related risks include feeling like you want to faint or feeling lightheaded, blood accumulating below the skin, bleeding excessively and infection.
MedlinePlus. (2009). ELISA/Western Blot Tests for HIV. Retrieved on March 22, 2011 from MedlinePlus: https://www.nlm.nih.gov/medlineplus/ency/article/003538.htm
PubMed Health. (2009). Systemic Lupus Erythematosus. Retrieved on March 22, 2011 from PubMed Health: https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001471/