At first glance, the small white plastic box looks unobtrusive: It's no bigger than the smartphone it's attached to. But its inventors think it can accomplish great things: It will deliver a safe HIV diagnosis in only 15 minutes, without an external power supply or other expensive laboratory equipment. Tassaneewan Laksanasopin, one of the developers at Columbia University in New York, says her team is aiming to build a device that would be especially useful for HIV screening in rural areas and would prevent many HIV transmissions.

How it works

Performing the test is a simple matter. A finger-prick provides enough blood for the test. The droplet is placed in a plastic collector containing reagents that respond to disease-specific antibodies. This is then inserted into the testing unit, which is connected to the phone's headphone jack, from which it draws all its power.

Pressing on a mechanical rubber bulb creates a vacuum that draws in the blood; this also reduces power needs compared to the electric pump in other tests. A chip then checks for antibodies, while an app analyzes the results. A clear diagnosis then follows.



The test is easy to use. Pressing on the rubber pump draws the blood into the reagent chamber, where testing takes place

Laksanasopin said her device offered several advantages over the low-cost test methods that are already on the market. These, she said, often deliver unclear results or results that are difficult to interpret.

The tests are estimated to cost around 34 dollars each, one-thousandth of the cost of the expensive laboratory equipment that would otherwise be necessary.

"The device can be reused but the plastic chip is single-use," Laksanasopin said. Social workers in particular could use the device in rural areas to quickly provide a reliable diagnosis. At room temperature, the reagents are stable up to six months - an equally important factor for use in developing countries.

An accurate diagnosis?

The diagnostic accuracy for HIV is close to 100 percent, Laksanasopin said. But this value refers only to the sensitivity of the test, indicating only the certainty with which it recognizes HIV infection. In practice, this high certainty means it may produce false-positive test results. "If you get a positive result, there'll be a chance it'll be false - around 8 percent," Laksanasopin said.

In the event of a positive diagnosis, follow-up tests would therefore be needed, she said. However, this is also standard practice for other HIV tests for personal use.

Laksanasopin and her team have been working on the HIV test for eight years. But even more time will pass before it can be used. "In our testing, there have been 96 people," she said. "It's a very small number." More stringent testing will be needed to bring it to the world market - along with certification by the World Health Organization. The WHO aims to ensure that only safe products go on the market, even in countries with poor medical infrastructure.

But Laksanasopin says the need for the test has been an important motivating factor. Making testing more widely available would allow people to get help sooner. And pregnant women would be able to prevent the disease from passing to their children, she said.