A new blood test shows promise as a rapid way to help doctors determine whether a respiratory infection is viral or bacterial and thus reduce inappropriate use of antibiotics, which only work against bacteria.
The study is published in the journal Science Translational Medicine.
Study co-author Geoffrey Ginsburg, a professor at Duke University School of Medicine, says:
"Current tests require knowledge of the pathogen to confirm infection, because they are strain-specific. But our test could be used right away when a new, unknown pathogen emerges."
He explains the new test would be especially useful for spotting new viruses before they spread into outbreaks.
For example, in the case of pandemic flu or MERS, the new coronavirus that has erupted in the Middle East, it would be very important to diagnose new cases quickly, much faster than current diagnostic tests.
The new test uses a different approach to traditional diagnostics: instead of testing the pathogen, it tests the immune response in the infected person.
Using an approach called "reverse transcription polymerase chain reaction (RT-PCR)," the test evaluates how strongly certain genes in immune cells and other cells in the blood are switched on.
Previous studies have shown these genes are more active in people with respiratory infections caused by viruses. They are not switched on in healthy people or those whose infection is caused by bacteria.
In their study, the team describes how they evaluated the test in a group of over 100 people and found it was able to identify, with nearly 90% accuracy, the ones with viral infections.
The group comprised patients (some with viral infection, the rest with bacterial infection) and healthy controls. The patients had attended a hospital emergency department complaining of fever.
The test positively identified viral infection in 89% of cases, and it correctly ruled out viral infection in 94% of cases.
The team concludes:
"These results show that RT-PCR-based detection of a host gene expression signature can classify individuals with respiratory viral infection and sets the stage for prospective evaluation of this diagnostic approach in a clinical setting."
Christopher W. Woods, co-author and an associate professor of medicine, pathology and global health at Duke and the Durham VA Medical Center, says bacterial resistance, which is largely driven by overuse of antibiotics, is a big global public health problem, causing infections that are increasingly difficult to manage:
"A tool that enables us to accurately identify viral infections could curb the indiscriminate use of antibiotics and reduce the development of resistant pathogens."
The US Centers for Disease Control and Prevention (CDC) says taking antibiotics for viral infections can do more harm than good, citing for instance, that where children are concerned, antibiotics are the most common cause of emergency department visits for adverse drug events in the US.
The team is now working to reduce the time it takes for the test to report results.
It currently takes 12 hours to analyze 30 genes, so Prof. Ginsburg says there is scope to reduce both the time and the number of genes.