What has to develop in order for a test be positive HIV?

In the case of an HIV test, the development of antibodies to the HIV virus is what leads to a positive test result. These antibodies are produced by the immune system in response to infection with the HIV virus. After exposure to the virus, it can take several weeks or months for the antibodies to develop, so during the early stages of infection, an HIV test may return a negative result. This period of time is known as the "window period". For this reason, if an individual suspects recent exposure, it is important to follow-up with additional testing to ensure an accurate diagnosis.