A Quick, Cheap Diagnostic Test for HIV and Other Infections

Quick test for HIV: This microfluidics chip can detect syphilis and HIV in just 15 minutes from one microliter of blood.
Credit: Curtis Chin, Columbia University

BIOMEDICINE

A simple microfluidics chip could improve health care in poor countries by making rapid diagnostic testing a reality.

• BY EMILY SINGER

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A small plastic chip that costs just 10 cents to make can reliably diagnose HIV and syphilis within about 15 minutes. The chip, which is based on microfluidics, uses small wafers that precisely manipulate nanoliter volumes of fluid in order to carry out a sequence of chemical reactions.

Developed by Samual Sia and collaborators at Columbia University, the system was designed to be used in resource-poor settings. Field tests in Rwanda showed that the chip works as well as traditional laboratory-based HIV diagnostics. Sia wants to deploy the test in prenatal clinics in Africa.

Many health clinics and even city hospitals in Africa must send out blood samples to a national laboratory for processing—a process that can take days or weeks. But in poor, rural areas, where patients may have to travel days to reach a clinic, many people are unlikely to return for a second visit to get their results. Tests that give reliable results in minutes could make a huge difference by letting the physician treat the patient during the visit.

While rapid diagnostic tests for HIV and some other infections already exist, they are typically not used in poor areas of Africa because they are more complicated to read and more expensive to use. Such tests are limited to detecting a single disease per use. With Sia's chip, additional tests, such as for hepatitis or malaria, can be added to the chip without increasing the cost significantly.

To make microfluidics technology more practical to use in poor countries, Sia's team designed it to be inexpensive to make and easy to read, and then tailored manufacturing methods for those purposes. The chips are produced via a plastic injection molding process that has been optimized to create nanoscale features. The reagents for the detection reaction are stored in a tube, separated by bubbles of air, and brought into the chip with the simple pull of a syringe.

The process requires no moving parts, electricity, or external instrumentation, and it requires a very small amount of blood—about one microliter. Unlike many microfluidics devices, the results can be read without microscopes or other expensive optical systems. A simple optical sensor on an instrument that's about the size and cost of a cell phone gives the test results.

Sia's team worked with Columbia's School of Public Health, the Rwandan administrator of health, and nongovernmental health organizations to test the device in Rwanda's capital city of Kigali. As many as 8 percent of women in Kigali are HIV positive, and it can take days or weeks to get the results for HIV tests at the hospital because blood samples must be sent to an outside lab for analysis. When Sia's device was used to test for HIV, and HIV and syphilis in combination, it detected 100 percent of cases, with a false positive rate of about 4 to 6 percent—on par with standard laboratory tests. The findings were published today in the journal Nature Medicine.

Recognizing the challenge of raising funds to commercialize a technology for poor nations, Sia and two partners founded a company called Claros Diagnostics. They won venture funding to develop a device for use in doctors' offices in wealthy countries to monitor signs of prostate cancer—a device that garnered marketing approval in Europe in June. Sia's team at Columbia then adapted the technology to test for sexually transmitted diseases; in addition to HIV and syphilis and hepatitis, they are working on tests for hepatitis B and C, herpes, and malaria. While the test was developed for use in poor countries, it might ultimately find appeal elsewhere as well.

Sia's initial focus is on prenatal clinics. "If you catch the diseases in mothers, you can prevent transmission to newborn, increasing clinical impact," says Sia. According to the research, syphilis testing in mothers and pregnant women could reduce the number of years lost due to ill health, disability, or early death by 200,000 in Rwanda.

Sia and his collaborators still face a major hurdle: finding funding to develop the STD device into a commercial product. While the researchers won grants and garnered venture-capital funding to develop the technology, including money from the Gates Foundation to find the best market, they have yet to secure funds to widely implement the technology. Ironically, the Gates Foundation declined to fund the next step in development, though research showed that STD testing was the optimal market to apply the technology.