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Bringing flu testing closer to home
INDIANAPOLIS, Ind.—As flu season fast approaches, we are once again reminded of the severity and costliness of influenza, which every year kills an average of 36,000 Americans, sickens millions more, and runs rampant through many schools and workplaces in the United States and around the world. In a presentation at the 246th National Meeting & Exposition of the American Chemical Society (ACS), however, researchers unveiled emerging technology that may pave the way for widespread at-home testing for influenza and revolutionize treatment and prevention of the disease. Drs. Suri Iyer of Georgia State University in Atlanta and Allison Weiss of the University of Cincinnati have developed new technology that uses carbohydrates to detect flu virus antigens, or proteins on the flu virus' surface.
The U.S. Centers for Disease Control and Prevention (CDC) recommends on its website that patients who suspect that they may have the flu should stay home and avoid contact with others, only contacting a healthcare provider if they are in a high-risk group or if they become severely ill. Unfortunately, flu symptoms are fairly nonspecific—cough, sore throat, runny or stuffy nose, body aches and sometimes fever—and can resemble other common maladies ranging from the common cold to allergies. Identifying influenza early can help sick patients know to avoid contact with others, and opens up the possibility of treating the illness with antiviral drugs, which become more effective the earlier they are administered, the CDC website says.
Influenza is typically identified using conventional viral cell cultures, which are largely accurate but typically take three to 10 days to yield results in a lab. This wait time generally leaves patients outside the window during which antiviral drugs would be effective in mitigating the disease.
"Just going to the doctor's office or hospital for diagnosis can be counterproductive during a major flu outbreak," Iyer explained during the ACS presentation. "It carries the risk of spreading the disease. During the last swine flu outbreak, hospitals in some areas went on TV to tell people not to come to the ER. Not only could they spread the virus, but ERs did not have the facilities to test hundreds of worried people."
An alternate option for influenza testing is rapid, point-of-care diagnostics that use antibodies to detect the presence of the flu virus, and can yield results in minutes. These antibody tests, however, generally suffer from a lack of reliable sensitivity—the CDC reports that product insert information and published research grade these tests' sensitivities at between just 50 and 70 percent, resulting in a substantial number of false negatives.
As such, antibody-based point-of care diagnostics are primarily used for surveillance, monitoring outbreaks and trends rather than positively diagnosing an individual patient. Even for this purpose, however, antibody tests have their limitations. Antibodies for new, emerging flu strains are difficult to procure. Furthermore, the antibodies degrade rapidly if kept at ambient temperature without refrigeration, making shelf life a serious constraint in remote, low-resource areas with intermittent or no electricity where some emerging strains originate.
Current antibody based tests can cost upwards of $50 per test, depending on the manufacturer, making them a costly option for large-scale screening efforts, and pricing them out of reach of many families who would consider using them at home. The development of an inexpensive at-home test would dramatically change the face of flu season.
"At-home testing would help because parents can decide if their child is sick," says Iyer. "Since influenza is a respiratory pathogen, keeping the child home would arrest the spread of the disease. In fact, when a person with influenza sneezes, the virus spreads all over the room. So, home testing is very important."
The new testing technique also has implications in the emergence of new flu strains. Flu viruses have two major antigens—hemagglutinin and neuraminidase—that determine the specific strain of flu virus. Changes in hemagglutinin or new combinations of hemagglutinin and neuraminidase signal the emergence of a new strain of flu, such as the H1N1 "swine flu" that emerged in the spring of 2009.
The new test technology uses various forms of carbohydrates that can capture the hemagglutinin and neuraminidase, and can simultaneously positively confirm an infection of influenza and identify the specific type or strain of flu virus via a color change or other signal. Identification of the specific flu strain would enable doctors to administer the most appropriate antiviral drug.
"We are developing a library of carbohydrates (or glycans) that bind to the virus, however, each molecule binds with slightly different affinity," says Iyer. "When a library of glycans in a microarray format is exposed to a single strain of virus or an emerging strain, each strain would give rise to a unique 'fingerprint,' which could potentially be used to identify the particular strain."
The new approach has other potential advantages over today's options, including rapid, point-of-care results, drastically lower costs and greater reliability.
Iyer and Weiss plan to move ahead this fall with tests on samples taken from human volunteers. Their vision is for a package similar to a strep throat or pregnancy test that gives an easy-to-read color change, priced perhaps around $10 or less, to make it affordable for parents of school-aged children to keep a flu test in the medicine cabinet.
"While I believe that we are quite capable of developing prototypes for testing, to further develop it into a viable commercial product that could be used in a primary care setting or at home will require significant investment from private investors or something like a public-private venture," says Iyer.