Definition This is a test that detects the presence of antibodies, which are chemicals produced by the body to fight germs and other foreign substances. In particular, the test detects antibodies to the human immunodeficiency virus (HIV) which causes acquired immunodeficiency syndrome, or AIDS.
How is the test performed? A blood sample is needed to test for HIV antibodies. This is obtained by drawing blood from a vein in the forearm or the hand. To do this, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube, or tourniquet, is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them. A very thin needle is gently inserted into a vein and the tourniquet is removed. Blood flows from the vein through the needle and is collected in a syringe or vial. The sample collected is then sent to the laboratory to be analysed. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.
What is involved in preparation for the test? A person having this test should receive instructions from a doctor on how to properly prepare. The HIV testing process can be the cause of much stress and concern. For this reason, some doctors may recommend counselling.
What do the test results mean? Since the HIV Western blot test is an antibody detection test, its results will not be accurate until an HIV infected person seroconverts. Seroconversion describes the process by which the body "reacts" to the viral infection by trying to defend itself through production of antibodies. This process occurs anywhere from 2-12 months after infection with HIV. However, most patients will seroconvert within 6 months. After an infected person has seroconverted, a positive western blot indicates that an HIV infection is present.
Author: David T. Moran, MD Reviewer: eknowhow Medical Review Panel Editor: Dr JOhn Hearne Last Updated: 1/05/2005 Contributors Potential conflict of interest information for reviewers available on request
