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Blood test could identify which patients need antibiotics


Antibiotics are drugs used to treat infections caused by bacteria, but they are ineffective against infections caused by viruses.

According to the Centers for Disease Control and Prevention (CDC), more than 262.5 million courses of antibiotics are written in the outpatient setting each year in the US, but around 50% of these are prescribed unnecessarily.

Misuse of antibiotics is a key contributor to antibiotic resistance; if a patient takes antibiotics for a viral infection, the drug will still attack bacteria in the body, but it will attack healthy or beneficial bacteria. This can cause antibiotic-resistant properties that can be passed on to other bacteria.
In the US alone, more than 2 million people become ill as a result of an antibiotic-resistant infection each year, and more than 23,000 Americans die from such infections.

Lead study author Dr. Ephraim L. Tsalik, assistant professor of medicine at Duke Medicine in Durham, NC, and colleagues note that a large proportion of unnecessary antibiotic prescriptions are for respiratory illnesses, which they say is largely fueled by the inability to identify the cause of such conditions.

"We use a lot of information to make a diagnosis, but there's not an efficient or highly accurate way to determine whether the infection is bacterial or viral," notes Dr. Tsalik.

But in their study, published in Science Translational Medicine, the team reveals how a simple, rapid blood test that can distinguish between bacterial and viral infections could be in the cards.

Test distinguished between bacterial, viral infections with 87% accuracy

For their research, Dr. Tsalik and colleagues enrolled more than 300 patients with respiratory infections who had presented to emergency departments at five hospitals in the US.

The team analyzed the patients' blood samples to assess gene signatures, which are patterns that show which genes are switched on and off - information that can be used to identify whether a person has a bacterial or viral infection.

Previously, the researchers pinpointed gene signatures that were linked to viral infections, but they note that this latest study is the first to distinguish non-infectious and viral infections from bacterial infections.

By measuring patients' gene expression profiles from blood samples, the team found they could use the previously identified gene signatures to correctly identify patients with flu viruses, rhinovirus, various strep bacteria and other common infections with 87% accuracy.
Based on their results, the researchers believe they are one step closer to creating a simple blood test that could aid antibiotic prescription practices.

Development of a 1-hour test in progress

There is one major barrier, however; at present, it takes around 10 hours to assess a patient's gene expression profile. But the team says they are in the process of working with developers to create a 1-hour test that can be used by clinicians.

Speaking about their goals with this research, senior author Dr. Christopher Woods, professor of medicine and associate director of the Genomics Center at Duke, says:
"The ideal scenario, should this test ultimately be approved for broad use, is you would go to the doctor's office and receive your results by the time you meet with your provider.
We are working to develop a test that could be run in most clinical labs on existing equipment. We believe this could have a real impact on the appropriate use of antibiotics and guide the use of antiviral treatments in the future."
Last September, Medical News Today reported on the development of a blood test that accurately detected 70% of lung cancer cases.

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