In Rwanda, the most densely populated country in Africa, there are approximately 190,000 people living with HIV, with electronic records facilitating care for over 90,000 of them. However, many thousands of HIV-infected people there who don’t have access to health centers remain undiagnosed.
It’s exactly this type of situation that Samuel Sia hopes to ameliorate. Sia, a biomedical engineer, and his team at Columbia University in New York have combined the portability of mobile technology with the detection potential of enzyme-linked antibodies to create a fully automated and portable microfluidic device dubbed the ‘mChip’. The scientists tested the device on serum, plasma and blood samples from over 200 HIV-infected individuals in Rwanda and published their findings in this month’s issue of Clinical Chemistry.
The device uses blood from a finger prick, similar to that employed by a glucose meter, which is automatically loaded onto a small fluidics chip that contains HIV-specific antibodies and reagents needed to perform an enzyme-linked immunosorbent assay, or ELISA. ELISA is the most sensitive and commonly used laboratory diagnostic for HIV, and historically has taken hours and sometimes days to provide a result. The mChip device, however, produces a result in just 15 minutes. Sia says that this shortened testing time does not sacrifice the specificity and sensitivity of the mChip, as it was 100% accurate in detecting HIV positive samples and 99% accurate in distinguishing HIV negative samples in the pilot study.
“This is a novel device and the diagnostic field is likely to move in this direction in coming years,” says Bharat Parekh, a laboratory chief at the US Center for Disease Control’s Division of Global HIV/AIDS in Atlanta, Georgia, who works on developing rapid HIV testing.
To Sia’s knowledge, the mChip device is the first rapid HIV test that uses cell phone network or satellite connectivity to automatically synchronize test results with patient health records anywhere in the world. “Now, with a single push of a button, there is automation not only from the sample to the result, but to the synchronization of data to the cloud,” Sia says, referring to the data repository that doctors can access. “This automation is very important because it minimizes user error and user variability.”
The HIV diagnostics realm has seen other user-friendly devices recently. Last July, the FDA approved OraQuick, manufactured the Pennsylvania-based OraSure Technologies, as the first in-home mouth swab HIV testing kit. According to Sia, though, when “there is a weakly positive sample [that’s] where you can’t tell.” In a head to head comparison of the mChip, OraQuick, and a standard laboratory HIV ELISA using a commercial panel of 23 HIV samples, the mChip correctly detected all 17 HIV positive and six weakly positive samples, whereas OraQuick missed the six weakly positive samples, with four registering as false negative and two as indeterminate. Weakly positive samples, such as those from recent HIV infections, can constitute 0.3% to 3% of HIV-infected patients in high-risk populations.
Parekh cautions that it is too early to say if the device will make a major impact for the developing world. There are several rapid tests currently in use that do not require any electrical power source and can be performed anywhere by properly trained personnel.
But Sia emphasizes that another advantage of the chip is that it can look for multiple diseases at once. “The real power is [that] one finger prick can give you multiple rapid test results, making it cheaper and more convenient.” Sia and his team published a paper in Nature Medicine in February 2011 that used an early prototype of the mChip to simultaneously diagnose HIV and syphilis in 67 samples collected in Rwanda, giving 100% and 94% sensitivity and 95% and 76% specificity, respectively.
For a closer look at the prototype, check out our video about that 2011 paper: