A blood test could help doctors better diagnose respiratory viral infections and reduce the unnecessary prescription of antibiotics, which are used to treat bacterial infections, reports a new study in the 18 September issue of the journal Science Translational Medicine.
The results suggest the new test could be a useful tool for hospitals and doctors' offices to help to distinguish between viral and bacterial infections early on.
"Current tests require knowledge of the pathogen to confirm infection, because they are strain-specific," said study co-author Geoffrey Ginsburg, a professor at Duke University School of Medicine. "But our test could be used right away when a new, unknown pathogen emerges."
The new test could prove especially useful in identifying potential viral outbreaks before they have a chance to become widespread, Ginsburg noted. "In instances such as pandemic flu or the corona-virus that has erupted in the Middle East, it's extremely important to diagnose a viral illness far more accurately and speedier than can be done using traditional diagnostics."
The new approach focuses on the host immune response to an infection, which differs based on the type of pathogen doing the infecting. The test works by evaluating how strongly certain genes are turned on or expressed from immune cells and other cells in the blood in the presence of viral or bacterial particles.
Earlier work has shown that certain genes are expressed in people with respiratory viral infections. These genes are not expressed in healthy people, or in people with bacterial respiratory infections.
The researchers used the test on 102 individuals arriving at a hospital's emergency department with fever; 28 had a viral infection, 39 had a bacterial infection and 35 were healthy controls. The test was able to spot patients with viral infections with almost 90 percent accuracy.
More specifically, the test provided true positive identifications of viral infection in 89 percent of the cases, and correctly ruled out the negative cases 94 percent of the time.
"One of the big global threats at the moment is the emergence of bacterial resistance, and that is largely driven by overuse of antibiotics," said Christopher W. Woods, an associate professor of medicine, pathology and global health at Duke and the Durham VA Medical Center, and co-author of the paper.
"This is a growing public health threat, creating infections that are increasingly difficult to manage," Wood said. "A tool that enables us to accurately identify viral infections could curb the indiscriminate use of antibiotics and reduce the development of resistant pathogens."
Additional work is ongoing to trim the amount of time it takes for the test results to be reported. Ginsburg said the test currently takes 12 hours to analyze about 30 genes. Both the time and the number of genes could be pared down, the author said.
Read the abstract, "A Host-Based RT-PCR Gene Expression Signature to Identify Acute Respiratory Viral Infection," by Aimee.K. Zaas and colleagues.