The rapid oral HIV test detects antibodies made by the immune system in response to HIV infection, just like the standard blood antibody test. The rapid oral test, however, detects these antibodies in oral fluid, and doesn't require a blood sample.

Like any antibody test for HIV, the rapid oral HIV test is not reliable during the "window period" (lasting several weeks to months) between the time a person is infected and the time the body has made enough antibodies for the test to detect. During this window period, someone who is infected might test negative for antibodies.

Oral rapid HIV tests have been shown to shown to have similar accuracy to the standard blood antibody test. However, it is possible to have false positive tests (person may have a positive rapid oral HIV test but not be infected with HIV). That's why anyone who has a positive rapid oral HIV test must have a more specific "confirmatory" test before a diagnosis of HIV infection can be made.