Investigators at the Brigham and Women’s Hospital have designed a portable and affordable cellphone-based diagnostic tool to detect HIV, which can have profound implications in developing countries and other resource-limited areas. The novel platform is described in a paper published in Nature Communications.
Detecting HIV as early as possible after infection is essential. It helps reduce the risk of transmission and enables treatment to be started right away. Several studies have shown that outcomes are best when antiretroviral therapy is started as early as possible, ideally when pretreatment T-cell counts are >500 cells/mm3. A significant challenge to this has been that most HIV tests look for HIV antibodies that can take many weeks after infection to become detectable in the blood and even longer to become detectable in other body fluids.
What makes the new cellphone-based test special is that it looks for HIV RNA in the blood, which is the first laboratory marker of HIV and can be seen as early as 7 days after infection. Although RNA-based tests have been available for a long time, they are expensive, invasive (requiring venipuncture), and resource-intensive (requiring processing at a special lab). Subsequently, in resource-strapped areas, such as developing countries or rural settings, such tests are rarely feasible. This has led to reliance on a variety of antibody-based tests in the field. And while these tests have been revolutionary because they can provide results quickly and do not require any special equipment, they might not be able to detect HIV if the infection is recent (<20 days; acute HIV). In contrast, if the infection has been present for some time, then these tests are just as sensitive in detecting HIV as an RNA-based test, with the caveat that the specimen used is a blood sample.
The new cellphone-based RNA test uses nanotechnology, a specially treated microchip, a cellphone, and a 3-D printed cellphone attachment to detect HIV RNA nucleic acids in a single drop of blood, reducing the risk of needlestick injuries or need to carry around any bulky equipment. The investigators reported 99.1% specificity and 94.6% sensitivity, which is on-par with laboratory-based RNA tests. However, unlike the expensive lab version, the total material cost of the test came to less than $5.
Currently, the test only assesses for HIV-1. While this is the most prevalent HIV strain worldwide, most tests on the market also assess for HIV-2. However, this tool is a work in progress that can have far-reaching implications for detecting other infectious diseases. “We could use this same technology as a rapid and low-cost diagnostic tool for other viruses and bacteria as well,” said lead author Mohamed Shehata Draz, PhD, in a study-related statement.