Test could show if infection is viral or bacterial

Being sick can be frustrating. Being prescribed medicine that doesn’t help your sickness can be even more frustrating.

This is often the case when viruses are mistaken for bacterial infections.

But a group of researchers hopes to create a definitive test for distinguishing the two.

A team at Duke Health says they are close to finalizing a test that can determine whether a respiratory illness is caused by infection from a virus or bacteria. Such a test would allow antibiotics to be more precisely prescribed.

Researchers said they have developed what they call gene signatures - patterns that reflect which of a patient's genes are turned on or off - to indicate whether someone is fighting infection from a virus or bacteria.

Results can be found from a small sample of the patient's blood.

The signatures were tested in a study described in the January 20 issue of Science Translational Medicine. They were found to be 87 percent accurate in classifying more than 300 patients' illnesses.

With these findings, Duke researchers believe they are a significant step closer to developing a rapid blood test that could be used in clinics to distinguish bacterial and viral infections, and to guide appropriate treatment.

"A respiratory infection is one of the most common reasons people come to the doctor," said lead author Ephraim L. Tsalik, M.D., Ph.D., Assistant Professor of Medicine at Duke and emergency medicine provider at the Durham VA Medical Center. "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. About three-fourths of patients end up on antibiotics to treat a bacterial infection despite the fact that the majority have viral infections. There are risks to excess antibiotic use, both to the patient and to public health."