Researchers from Columbia University have developed a low cost smartphone attachment that can quickly and accurately test for HIV, syphilis, and other sexually transmitted diseases.

The device, or dongle as it is called, costs only $34 to make and relies solely on power drawn from the smartphone. The device can test for three infectious diseases with just a finger prick worth of blood. Amazingly, this plastic device that is small enough to fit in the palm of your hand can perform all of the mechanical, optical, and electronic functions of a lab based blood test that usually costs over $18,000.

The developers traveled to Rwanda to test the dongle. There, they met with healthcare workers who administered the smartphone blood test on 96 pregnant women who were at risk of passing sexually transmitted diseases on to their children. The results were compared with outcomes of a standard enzyme-linked immunosorbent assay (ELISA) testing.

The smartphone’s results had close to the same level of accuracy. In order to prove the effectiveness of the test, the researchers measured how frequently the device could correctly identify the antibodies that indicated the presence of a sexually transmitted disease. This is known as ‘sensitivity’. In testing for HIV, the dongle had a sensitivity level of 92 to 100 percent, meaning it is very precise. For syphilis, the sensitivity level was 70 to 80 percent. While this is not as high as the researchers would have liked, it is still more than 10 times more accurate the non-lab based diagnosis. That is, when local doctors conclude a patient has a disease based exclusively on visible symptoms.

The Columbian team’s device has two major advantages over traditional lab tests. First and foremost, it is cheap. The device is made of a disposable piece of plastic that greatly resembles an audiocassette. It is preloaded with reagents that provide objective read outs of three disease-specific zones.

The second great advantage of this device is that it runs on very little electricity. This is a huge benefit for remote areas with unreliable power supplies. So long as someone in the area has any kind of smartphone, the dongle can be plugged into the headphone jack and test patients.

The team is planning a second, larger clinical trial in the hopes of getting approval from the World Health Organization to use the device throughout the developing world.