Disease detection on a dongle

February 4, 2015 § Leave a comment

A smartphone dongle with a disposable microfluidic cassette. [Credit: Tassaneewan Laksanasopin]

A smartphone dongle with a disposable microfluidic cassette.
[Credit: Tassaneewan Laksanasopin]

A handheld device powered by a smartphone can diagnose HIV and syphilis in Rwanda. In a paper just out in Science Translational Medicine, researchers describe the design and deployment of the dongle that carries three immunoassays to test for HIV and syphilis from a fingerprick of blood. It is the first diagnostic device for sexually transmitted diseases that brings together different assays into one field test.

Samuel Sia at Columbia University, who spearheaded the work, says that the World Health Organization recommends that researchers develop new tests for HIV and syphilis because the two diseases carry the highest risks for mother-to-child transmission in pregnant women. “We have verified that with our field surveys of healthcare workers in developing countries,” notes Sia.

Field tests used today to diagnose HIV and syphilis are not always accurate. The tests usually require an ELISA instrument that costs thousands of dollars, and it can take more than 2 hours to generate results (in developing countries, because of infrastructure issues, patients often wait at the healthcare center for the test results to come out).

The dongle developed by Sia and colleagues is estimated to cost $34 to make, and it spits out a result in 15 minutes. The microfluidic device plugs into the audio jack of a smartphone, such as an iPhone or an Android. Sia and colleagues showed that a fourth-generation iPod touch can power the dongle 41 times on a single charge.

The microfluidic device accommodates five different assays embedded in disposable plastic cassettes divided into zones.  “Each zone has a different affinity-capture molecule,” says Sia. The molecules pick up antibodies against HIV and syphilis. The investigators also built in negative and positive controls.

When tested at healthcare centers in Kigali, the assays worked almost as well as the conventional ones. Most of the 96 patients on whom the device was tested said they preferred the dongle over the conventional ELISA tests because it was quicker. Some did say they liked the fact they could be tested for more than one disease in one shot.

Notably, “this trial was the first to have healthcare workers run the tests instead of our research team members,” says Sia. “We were all pleasantly surprised at how well the test performed the first time, but that is not to say there is no room for improvement.”

Besides improving the dongle, Sia says he and colleagues are exploring how make it into a commercial product.

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