When Antibiotics Are Necessary — Or Not

Blood test may determine when antibiotics for respiratory infections are necessary

/ Author:  / Reviewed by: Beth Bolt, RPh

(RxWiki News) The common cold sends more people to the doctor than just about any other illness. Some patients need antibiotics, but it can be hard to decide which ones. That all may be about to change.

Researchers at Duke Health are refining a test that can distinguish between a cold caused by a virus and a cold caused by bacteria.

Lead study author Ephraim Tsalik, MD, PhD, said in a press release, "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."

Dr. Tsalik is an assistant professor of medicine at Duke.

Colds are typically caused by viruses, for which antibiotics are not effective. Taking antibiotics when they're not necessary increases the potential for negative side effects and antibiotic resistance.

To conduct this test, Dr. Tsalik and team looked at patterns they call gene signatures, which can be obtained from blood samples. These patterns identify which genes are turned "on" or "off," an indication of whether a patient is fighting a virus or a bacteria.

So far, the test has been 87 percent accurate in identifying whether a patient's cold was caused by a virus or bacteria. The test also shows when no infection is present.

According to Dr. Tsalik and team, the new test is more accurate than tests for specific viruses or bacteria. One disadvantage, however, is that it takes about 10 hours to get the results.

Dr. Tsalik and team are currently refining the test to get results within an hour.

Researchers said this is the first test to show the difference between non-infectious illness, bacterial and viral infections at the molecular level.

This study was published Jan. 20 in the journal Science Translational Medicine.

The US Defense Advanced Research Projects Agency, the National Institutes of Health, the Agency for Healthcare Research and Quality, and the US Department of Veterans Affairs Office of Research and Development funded this research.

No conflicts of interest were disclosed.

Reviewed by: 
Review Date: 
January 19, 2016
Last Updated:
January 22, 2016