The OraQuick Advance device holds a test strip. High up on the test strip, within the plastic casing, a substance with the makeup of HIV antigens has been applied. A patient places the end of the test strip in his or her mouth and swabs his cheeks and gums. The test administrator then places the end of the device in a vial that holds an enzyme solution that reacts to any antibody-antigen binding. As the oral fluid and the enzymes make their way up the test strip, they encounter the HIV-antigen substance. If there are HIV antibodies in the oral fluid, they start to bind to the antigens, and the enzyme reacts, causing a color change on the strip. This produces a line on the read-out portion of the device. This line indicates a reaction -- it is not considered to be a definite positive. As with all other HIV tests, OraQuick requires a repeat test before a patient is considered to be HIV positive. If no line appears at the site of the antigen substance, that's considered a negative result (no HIV antibodies present).