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August 01, 2011

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


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

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.

Nature Medicine - Microfluidics-based diagnostics of infectious diseases in the developing world



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.

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.

47 pages of supplemental information

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