The race to engineer a faster Ebola test

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Credit: Michel du Cille/The Washington Post via Getty Images

Ebola is still on a tear in three West African nations: the World Health Organization now estimates that while nearly 5,000 deaths have been reported, another 5,000 could be missing from the count, and more money is starting to find its way toward better healthcare infrastructure and an Ebola vaccine. From Facebook’s recently-unveiled initiative, which includes a “donate” button at the top of every newsfeed, to President Obama’s $6 billion emergency funding request, there is now a larger, more concerted effort to tackle the epidemic at its source.

Beyond building infrastructure and vaccines, however, is the race to engineer a faster Ebola test. The current gold standard used by the Centers for Disease Control and Prevention is called a real-time RT-PCR assay (RT stands for reverse transcription and PCR for polymerase chain reaction), which is a way of detecting a targeted DNA molecule by amplifying it, often with fluorescent dyes, to be able to detect a virus in even tiny quantities. Specimens are often sent to the CDC or WHO (the Dallas samples were sent to Austin, Texas), often adding a travel day to the two to six hours it tends to take to get a result. The tests are considered to be highly accurate, but they’re slow, cost $100 a pop, and require a tube of blood.

In places like Liberia, however, where patients finding their way to clinics are presenting acute symptoms like high fevers and vomiting, the tests don’t necessarily need to be the most sensitive given the viral load is likely high. They need to be fast, especially as the number of cases continues to grow and the current system, which requires sending tubes of blood to one of a handful of testing centers, is already backlogged. Even better if the tests also cross-check for other possible (and in some places more likely) causes, like malaria and Lassa fever.

“People are waiting four to five days” for test results, Dr. J. Daniel Kelly, who is working in Sierra Leone for the aid group Wellbody Alliance, told the New York Times. “They are watching people around them die. Horrible experience. You are locked in there at night.”

Minutes, not hours

Researchers at Harvard say they’re making progress with a test that delivers results in under an hour, while another team in France says it’s working on a test that could give results in as few as 15 minutes, and could be ready for prime time in early 2015. And in San Diego, the company Genalyte says its test takes just 10 minutes and will be ready in early 2015 as well, providing it can jump through all the regulatory hoops and hurdles that fast.

Genalyte's Ebola testing kit

Genalyte’s Ebola testing kit

“In the United States, we need an early detection test, to test everyone this person came into contact with, and we throw millions of dollars at every case,” Dr. Cary Gunn, the founder and CEO of Genalyte, told me. “But that’s not going to happen in the third world, and the place you have to solve this is in the third world.”

Many groups, including the World Health Organization, are encouraging the speedy development of rapid tests, and the Food and Drug Administration is giving emergency authorization to push qualified tests to market. (One test, BioFire’s Defense FilmArray, was just approved this way. While it is a faster, accurate one-hour PCR test, it still requires being transported to other sites, which takes up the bulk of the time lag.)

While some worry this is creating a bit of a Wild West atmosphere as researchers rush to get their tests approved, some of which may be far inferior to others, there is a silver lining: It could be a matter of weeks before we see a faster, more affordable screening tool deployed to clinics throughout Liberia, Guinea, and Sierra Leone.

Simple technology for a complex problem

For the most part, the tech is old school. Many faster tests use lateral flow strips (think of a pregnancy test) where antibodies bind to an Ebola virus protein. All that’s required is a finger prick of blood on the strip and a tube with a solution that reveals a line if the virus is present. These tests can take as few as 15 minutes, but like home pregnancy tests, they’re not nearly as accurate. In the case of Ebola, false positives could place people without Ebola in contact with other infected patients, while false negatives could release Ebola patients back into the public.

Genalyte’s $10 10-minute finger prick test developed in San Diego (with the cost of hardware comparable to BioFire’s) is unique. Unlike the lateral flow approach – which Gunn likens to developing film: “there’s a lot of funky chemistry to make them work and timing is finicky” – Genalyte has spent seven years developing a totally new approach. By placing an array of sensors on one tiny silicon chip, it is able to avoid the many manual (and thus variable and messy) steps involved in sample prep that comprise the bulk of testing time.

“It’s like developing a black and white photograph in a dark room – it’s not until the very end that you know whether or not that test worked,” Gunn said. “We’re like a digital movie. We are reading the test constantly. We get a movie of each test happening, so you’re able to see everything happen in real time. There’s no chemistry involved. It’s just straightforward watching the compounds and we see that binding happen directly. So it’s a fundamental new diagnostic technology.”

Eliminating the sample prep, Gunn said, is “revolutionary” – and it should be able to test not just for Ebola, but for all types of infectious disease (including influenza), as well as allergy testing and autoimmune testing. Gunn’s approach seems to be so promising that he said even the FDA is cooperating. “I spend most of my life throttled by the FDA and complaining about them and talking about how I could get diagnostic tests out quicker if not for them, however in this case they’ve been amazing to work with so far.”

Genalyte’s Ebola test could be ready for prime time – and fast-tracked for FDA approval – by early 2015. Gunn also hopes to add the simultaneous screening of other viruses and parasites, like Lassa fever and malaria, as quickly as possible. Stay tuned.

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