These tests use a small sample of blood taken from a vein in your arm to find out if you’ve been infected with HIV.The tests look for antibodies to HIV, not for HIV itself. HIV antibodies are made by B cells as your body tries to get rid of HIV. Labs use two tests to look for these antibodies. The ELISA test is done first, as a general screening test. (ELISA stands for “enzyme-linked immunosorbent assay.”) If the ELISA test is positive, a second test, called the Western Blot, is done to confirm the results. When both tests are positive, it means that the antibody to HIV has been found. Again, these tests don’t look for the virus itself, but for evidence in your blood that your immune system has reacted to the presence of HIV.