Why do false nonreactive (negative) HIV test results occur?
A false HIV-negative result may occur through the use of an HIV test that has low sensitivity as the initial assay within a national algorithm. Other factors may include early/acute infection (the window period), very advanced HIV disease where a person’s immune system is so compromised that HIV-antibodies are no longer being produced in high enough levels to be detected on standard HIV antibody tests, as well as user errors such as reading test result too early or mislabelling specimens or results. As mentioned above, another factor that can cause false nonreactive (negative) results occurs when people with HIV who on antiretroviral therapy seek additional HIV testing.