On the Horizon: A Better HIV Saliva Test

Researchers from Stanford University have developed an experimental saliva test for HIV infection that could be more sensitive than saliva tests currently on the market as well as easier to administer and less invasive than blood tests. The test also poses less risk of transmission during sample collection compared to blood. Preliminary studies of the new test were small, so more research is needed to determine the true performance (i.e., sensitivity and specificity) of the test. Ultimately, the researchers see the saliva test increasing HIV screening rates for at-risk populations and enabling earlier diagnosis and treatment for people who test positive for HIV compared to current saliva tests.

In response to HIV, the immune system produces antibodies to fight the infection. While HIV antibodies are present in saliva, the concentration is low compared to levels in blood. This variation in antibody concentration is why blood tests for HIV antibodies are more sensitive than saliva tests.

Even though modern HIV blood tests performed in laboratories are very accurate, there is a need for an improved saliva test for HIV antibodies. Because the samples are easier to collect and less invasive, saliva-based tests could improve screening rates. According to the Centers for Disease Control and Prevention (CDC), early detection is key to stopping the spread of HIV because early treatment with antiretroviral therapy (ART) reduces transmission rates. ART reduces HIV levels in the blood, reduces the risk of transmitting the infection to others, and lowers the risk of HIV-related complications like pneumonia and tuberculosis.

The Stanford University researchers, along with their colleagues at the Alameda County Public Health Laboratory, developed and conducted preliminary trials of their new saliva test for HIV. The Stanford test measures low levels of HIV antibodies in saliva by using virus antigens attached to DNA as part of the signaling system, which can be amplified and detected using standard laboratory instruments. They claim that their new test may be 1,000 to 10,000 times more sensitive than existing saliva tests and could therefore detect HIV infection earlier than current saliva tests.

Results from a preliminary study with volunteers showed that the new test correctly diagnosed 22 people with HIV and 22 people without HIV. Of eight saliva samples that returned indeterminate results (not clearly positive or negative) with a test currently on the market, six were flagged as positive by the new test.

The potential benefit of testing more patients for HIV in a more convenient manner is very attractive for disease prevention purposes. The researchers hope to replicate these results in larger studies in the future that include many more participants and samples.