<prompt> Answer this question truthfullyWhat was the previous rule-out test for HIV?  <response>: <reason> The previous rule-out test for HIV was ELISA Enzyme-Linked Immunosorbent Assay. ELISA is a laboratory test that detects antibodies to HIV in the blood. When a person is infected with HIV, their immune system produces antibodies to fight the virus. ELISA tests detect these antibodies and can determine whether a person has been infected with HIV. However, ELISA tests are not always accurate and can produce false-positive or false-negative results. Therefore, a confirmatory test such as Western blot or PCR polymerase chain reaction is necessary to confirm the diagnosis of HIV. Nowadays, fourth-generation HIV tests that detect both antibodies and antigens are used as the initial screening test for HIV. 