Highly-Sensitive Saliva Test Could Diagnose HIV Earlier

Public health officials face a dilemma with HIV testing: whether to give patients a reliable blood test that less patients will undergo or to administer a simple, yet less reliable, saliva test.

However, new findings from a study published by the Proceedings of the National Academy of Sciences suggest that a novel test can combine the convenience of a saliva test with the accuracy of a blood test for diagnosing HIV.

“The earlier you can detect, the better, because people can infect other people,” said researcher Carolyn Bertozzi, PhD. “Every day that goes by that a person’s behavior is not modified based on their HIV status is a day that they could be infecting other people, especially for young people.”

Current tests analyze the blood for antibodies rather than searching for HIV itself. The drawback to this method is the abundance of used needles, which, if not handled properly, could further the spread the disease, according to the authors.

“There’s a lot of populations you just can’t reach out to by blood tests,” said lead author Cheng-ting Tsai, PhD. “But if you were to do oral fluid, then all of sudden you open up a brand new population that was not otherwise accessible to you.”

Saliva-based tests also come with challenges, including HIV antibodies not accumulating in the numbers necessary to detect the infection early on, according to the study. The authors noted that oral HIV tests typically cannot detect HIV until later on, which means the virus could have been transmitted in the meantime.

In the new study, the authors examined the actions of antibodies rather than the proteins themselves.

The researchers said antibodies have 2 arms that can latch onto a virus. Then, they took parts of the virus and attached it to half of a piece of DNA and added modified HIV bits into a saliva sample.

The authors discovered that if the sample included HIV antibodies, the arms would grab the tagged HIV, which combined the halves of the DNA and made it easier to detect using current techniques.

This approach can be done without a blood sample or advanced technology to evaluate the sample.

“It’s purposefully low tech,” Dr Bertozzi said.

This test was validated in 22 HIV-positive patients who were screened using the new saliva test and conventional methods. The authors noted that the test did not give a false-positive result in 22 HIV-negative patients.

The authors hypothesize that the new test may also help detect new cases of HIV earlier than existing saliva tests; however, it may not produce earlier results than blood tests.

“Our hope is that we can get an earlier read than the present oral test because the sensitivity is better,” Dr Bertozzi said.

Notably, these principles could be applied to tests that screen for allergies, typhoid, and tuberculosis. The researchers are currently exploring this method to test the efficacy of measles vaccination.