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New Blood Test Accurately Sorts Viral vs. Bacterial Infections

Genomic assay may help curb unnecessary use of antibiotics (September 18)

A blood test developed by researchers at Duke Medicine showed more than 90% accuracy in distinguishing between viral and bacterial infections when tested in people with respiratory illnesses.

The test, which detects a specific genetic “signature” that the sick person’s immune system expresses as a response to the virus, demonstrates a potential new method for diagnosing the source of illnesses that have long been difficult to pinpoint.

Reported in Science Translational Medicine, the finding moves the technology closer to clinical use, where it could help patients get quicker diagnoses and treatments, while curbing the unnecessary use of antibiotics, which don’t work on viral infections.

When infected by a virus, a person’s immune system responds differently than when fighting a bacterial infection. These differences are evident at the genetic level, where certain genes are switched on during a viral attack, creating a fingerprint that broadly identifies the culpable pathogen.

In previous work, the Duke team described the development of a blood test, using a special assay, to identify approximately 30 genes involved in the immune response to viral infection among volunteers who had agreed to be infected with a series of common upper respiratory viruses.

The current study was a trial run of the blood test in a “real world” setting. Among 102 people arriving at a hospital’s emergency department with fever, 28 had a viral infection; 39 had a bacterial infection; and 35 were healthy controls. Using the test, the researchers were able to accurately classify more than 90% of the patients as having a viral infection or not.

The assay provided true positive identifications of viral infection in 89% of the cases, and correctly ruled out the negative cases 94% 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 co-senior author Christopher W. Woods, MD, MPH. “This is a growing public health threat, creating 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.”

Source: Medical Xpress; September 18, 2013.

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