‘Dongle’ turns smartphone into mobile lab to diagnose HIV, syphilis

Engineers have taken an ordinary smartphone and made it a whole lot smarter.

They created a compact, handheld device that plugs into an iPhone and turns it into a mobile laboratory that can diagnose HIV and syphilis in just 15 minutes.

The diagnostic device – the engineers call it a “dongle” – was tested on 96 patients who were being treated in three community health centers in Kigali, Rwanda. After getting their test results, 97% of the patients said they would recommend it to others, according to a report published this week in Science Translational Medicine.

Researchers from Columbia University developed the dongle to make it easier for healthcare workers in remote areas to identify people with life-threatening sexually transmitted diseases. The HIV and syphilis tests that are currently available cost as much as $8.50 combined and can take more than 2.5 hours to complete. By then, patients may be long gone.

A rapid, reliable test that can be performed anywhere would be a huge lifesaver in places like Rwanda, the engineers wrote. Previous research has shown that if a test like this correctly identifies 70% to 80% of people who are infected and 70% to 80% of those who are not, it would cut the number of deaths by a factor of 10 compared with a traditional test that is 100% accurate.

To make a device that fit this bill, the engineering team had to solve several problems. One of the challenges was to make the dongle simple enough for anyone to use after half an hour of training.

For the version that was tested, patients pricked their fingers to produce 1 microliter of blood. That tiny sample was then diluted and placed into a cassette that was already loaded with testing agents. After inserting the cassette into the dongle, the user had to squeeze part of the device to get the test going and press “start assay” on an app running on an iPod touch. The app, which would also work on an iPhone, then walked the user through a series of simple steps. After 15 minutes, the blood test results were displayed on the screen.

Another hurdle was to make sure the dongle could operate on very low power. The biggest power savings came from getting rid of a power-hungry electrical pump and replacing it with a squeezable rubber bulb to create a vacuum instead. (The bulb works like the ones on manual blood pressure monitors.)

In the end, the device was so efficient that it was able to run off the iPod’s battery power, which was relayed through the headphone jack. The research team was able to run 41 tests before the iPod had to be recharged. (Newer iPhones with longer battery life could probably run even more tests on a single charge, the research team noted.)

The dongle tested for the presence of HIV and performed two tests for syphilis. (With two tests, healthcare workers can tell the difference between active and past infections, thus avoiding over-treatment.)

How did it do? Very well, according to the report:

* The device correctly diagnosed all the patients who were HIV-positive and 87% of those who were HIV-negative. Twelve people got false-positive test results.

* For syphilis, one of the tests was 100% accurate and the other was 92% accurate at identifying people with the different types of antibodies. (There was one false-negative result.) They also correctly identified 79% and 92%, respectively, of the people who did not have those syphilis antibodies. That translated into 19 and 7 false positives.

* In interviews, 57% of the patients praised the test for offering quick results, 44% appreciated that it tested for multiple diseases at once, and 95% were happy to offer just a pinprick of blood instead of having to endure a typical blood draw from a vein.

All of this performance came at an extremely reasonable price, according to the study. The engineers estimated that their dongle would cost $34 to manufacture. The traditional lab equipment used to diagnose HIV and syphilis costs $18,450, they wrote.

“This kind of capability can transform how health care services are delivered around the world,” study leader Samuel K. Sia, a biomedical engineer at Columbia, said in a statement.

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