A new saliva-based test for HIV that offers results in 20 minutes may revolutionise the way in which HIV is diagnosed, researchers report.
The new test is based on oral mucosal transudate (OMT), a fluid that is secreted at the base of the gums before it becomes saliva. In fact, the level of antibodies in OMT is comparable to that of blood plasma, making it an excellent candidate for testing.
Same as pregnancy test
The underlying method, called immunochromatography, is the same as for pregnancy tests.
This technique aggregates the antibodies contained in the sample of oral mucosal transudate with the antigens (molecules recognized as enemies by the immune system) contained in the test.
The OMT is simply collected on a stick, which is similar to the one used in a pregnancy test, and then placed in a small tube containing a special solution. Between 20 and 40 minutes later a purple line will appear at the top of the stick if the result is positive.
To test the new technique under real world conditions, especially in vulnerable pregnant women, Dr Nitika Pant Pai, from Marina Klein’s research team at McGill University Health Centre, carried out clinical trials in the labour ward of the Mahatma Gandhi Institute of Medical Sciences, Sevagram, Maharastra, India.
“In such cases, it is vital to determine the HIV status of the mother very quickly to prevent transmission to the child during delivery. Many Indian women do not receive prenatal care and therefore do not get tested for HIV during pregnancy. Testing in the labour ward is the last chance to prevent HIV transmission to the newborn baby. Also Indian patients often refuse blood collection, while saliva collection poses no problem,” said Pant Pai.
In the study, 1 222 mothers were tested for HIV in a labour ward using both saliva and blood samples. The results from both kinds of tests corresponded in 100 percent of cases.
In addition, use of the saliva test in the labour ward helped identify several HIV infected women who were unaware of their HIV status. These women received treatments to reduce the chance of HIV infection in the newborn babies.
Long-term, the research may pave the way to a more widespread use of rapid oral fluid HIV tests to prevent mother to child transmission of HIV. It may also pave the way for an over-the-counter test for home use.
The study will appear in the May 6th, 2008 issue of PLoS Medicine (Public Library of Science, an open access publication). – (EurekAlert)