A promising new diagnostic test from MIT looks like it could be a game changer for rapidly diagnosing several important infectious diseases within minutes. While most tests can only look for one type of infection at a time, this can differentiate between Ebola, dengue, and Yellow Fever—three hemorrhagic fevers—at the same time.
Several things are especially appealing to me about the MIT point-of-care test, though some of the logistics are still being worked out. First is the test’s ease of use. The test will require little training, as it relies on technology similar to a pregnancy test, called lateral flow technology. A small amount of blood is directly applied to the strip, without needing to be processed in the lab. The fluid is drawn along a paper channel, and interacts with silver nanoparticles bound to monoclonal antibodies for the diseases.
Kimberly Hamad-Schifferli, visiting scientist and technical staff at MIT, collaborating with Lee Gehrke’s lab on this project, kindly walked me through the process. The silver nanoparticles turn different colors as they grow to different sizes, and are then bound to the antibodies. An easily read, color-coded band emerges if the blood carries any of these infections. The colors are readily seen by the naked eye, again requiring no special equipment. A mobile phone can capture the images of the test for confirmation and further data analysis.
These Matrix Multiplexed Diagnostic (MMDx) device kits, as other similar rapid diagnostics, are somewhat sensitive to humidity, so are packaged in foil with dessicants. The cost is expected to be in the $2-3 range.
Yellow Fever and dengue also occur in sub-Saharan Africa, so it is important to be able to distinguish between the different viral infections, as their spread and outcome are quite different, Ebola being the most contagious, as we’ve seen this past year. The other two are mosquito-borne infections. The addition of Yellow Fever should improve the accuracy of the tests, as there have been problems with cross-reactivity (mixing the two viruses up) in some other types of testing kits.
A similar rapid test, ReEBOV Antigen Rapid Test Kit (Corgenix, USA), was just approved by the World Health Organization (WHO) last week. This test is only for Ebola. The other problem is that the accuracy of that test is not great: the sensitivity was 91.8% and the specificity was 84.6%, lower than that for the benchmark PCR tests. This means that 8% of patients with Ebola would be missed by this rapid test, and 15% of people tested, although not ill with Ebola, would test falsely positive for the virus. Neither outcome has good consequences. Because of these inaccuracies, the screening should still be followed by the time-consuming confirmatory testing.
The MIT test is not quite ready for prime time, as it still has to complete testing to gain FDA approval. This, as with other Ebola diagnostics, is likely to fall under the Emergency Use Authorization (EUA), which allows for expedited approvals for problems deemed to be in the national security interest. The specific requirements for an EUA are a bit nebulous. I’ll update this if I get specific answers back to my inquiries.
In the meantime, the MIT lab—a large interdisciplinary team including researchers in infectious diseases, chemical and mechanical engineering, nanotechnology, molecular biologists and —continues to explore this technology for other important infectious diseases as well. This innovation could be a game changer.
Further reading:
Chun-Wan Yen, Helena de Puig, Justina O. Tam, José Gómez-Márquez, Irene Bosch, Kimberly Hamad-Schifferli and Lee Gehrke
