New test for Ebola dramatically cuts diagnosis time
Simple paper strip developed by MIT can diagnose Ebola and other fevers within 10 minutes
A new test from researchers at Massachusetts Institute of Technology cuts the time it takes to diagnose Ebola from at least a day or two, to just 10 minutes.
The device is a simple paper strip, similar to a pregnancy test. Not only can it rapidly diagnose Ebola, but also other haemorrhagic fevers such as yellow fever and dengue fever.
Time is of essence in Ebola diagnosis, to determine whether a patient requires immediate treatment and isolation, to prevent the disease from spreading further.
The current method of diagnosis involves a patient’s blood sample being sent to a lab, where advanced techniques are performed to detect genetic material from the Ebola virus. While this is very accurate, it takes at least a day or two to yield results.
Further, some areas of Africa where Ebola and other fevers are endemic have limited access to this kind of technology.
“For many hemorrhagic fever viruses, like West Nile and dengue and Ebola, and a lot of other ones in developing countries, like Argentine hemorrhagic fever and the Hantavirus diseases, there are just no rapid diagnostics at all,” says Lee Gehrke, a professor at MIT's Institute for Medical Engineering and Science who started developing the device with colleague Kimberly Hamad-Schifferli four years ago.
Hamad-Schifferli and Gehrke, are the senior authors of the paper describing the new device in the journal Lab on a Chip.
The new device is a colour-coded test that relies on lateral flow technology, which is used in pregnancy tests and has recently been exploited for diagnosing strep throat and other bacterial infections.
The strip uses nanoparticles that are made of silver and can take on different colours depending on their size. The researchers created red, orange, and green nanoparticles and linked them to antibodies that recognise Ebola, dengue fever, and yellow fever.
As a patient's blood serum flows along the strip, any viral proteins that match the antibodies painted on the stripes will get caught, and those nanoparticles will become visible. This can be seen by the naked eye; for those who are colorblind, a cellphone camera could be used to distinguish the colors.
"When we run a patient sample through the strip, if you see an orange band you know they have yellow fever, if it shows up as a red band you know they have Ebola, and if it shows up green then we know that they have dengue," Hamad-Schifferli says.
With the process taking only about 10 minutes, the researchers envision their new device as a complement to existing diagnostic technologies.
“If you're in a situation in the field with no power and no special technologies, if you want to know if a patient has Ebola, this test can tell you very quickly that you might not want to put that patient in a waiting room with other people who might not be infected,” says Gehrke, who is also a professor of microbiology and immunology at Harvard Medical School.
“That initial triage can be very important from a public health standpoint, and there could be a follow-up test later with PCR [polymerase chain reaction] or something to confirm.”
The researchers are now testing the device in the lab with engineered viral proteins, as well as serum samples from infected animals. They hope to obtain approval from the US Food and Drug Administration to begin using the device in areas where the Ebola outbreak is still ongoing.
According to the latest situation update from the World Health Organisation, as of February 15, there have been 23,253 total confirmed, probable and suspected cases of Ebola virus disease reported in nine countries.
However, the number of Ebola cases have fallen rapidly in the past two months, with about 10 times fewer people diagnosed with Ebola each week than in September last year.
A total of 128 new confirmed cases of the disease were reported in the week to Feb 15: 52 from Guinea (the first week-to-week decline since Jan 25); 74 from Sierra Leone, where transmission remains widespread; and two from Liberia.
According to the WHO, over 40 new confirmed cases were identified only when testing was carried out on samples from individuals after they died in the community, away from treatment facilities.
“Not only have these individuals not received potentially life-saving treatment, but other members of the community have been put at greater risk of exposure to Ebola virus disease than they would have been had those individuals been isolated when they first showed symptoms,” says the WHO report.
MIT’s new testing strip could perhaps prevent more of these cases from happening.
“Thankfully the Ebola outbreak is dying off, which is a good thing,” Gehrke says. “But what we're thinking about is what's coming next. There will undoubtedly be other viral outbreaks. It might be Sudan virus, it might be another hemorrhagic fever. What we're trying to do is develop the antibodies needed to be ready for the next outbreak that's going to happen.”