Do You Really Need An Antibiotic?

I understand there’s a new blood test that can tell you when you need to take antibiotics. How does it work? Should I ask for it if a doctor recommends antibiotics?

Andrew Weil, M.D. | April 12, 2016

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A sophisticated test that can differentiate between bacterial and viral causes of infections is in the works, but isn’t yet ready for general use. If and when it becomes available, the test could help eliminate the unnecessary use of antibiotics for viral infections. Researchers at Duke University, who are fine-tuning the test, say that about 75 percent of patients put on antibiotics for colds, flu and other respiratory ailments have viral infections for which the drugs don’t work. Needlessly taking them is a major contributor to increasing antibiotic resistance in bacteria and the emergence of “superbugs” the medications can’t treat.

The test looks at a small sample of blood to detect “gene signatures” – the response of your genes to the presence of infection-causing viruses or bacteria.

In a study published in January (2016), the Duke team reported that genetic signatures were 87 percent accurate in classifying what kinds of infections were occurring among about 300 patients with flu, colds, strep and other common respiratory problems. The test also revealed when no infection was present.

Lead author Ephraim L. Tsalik, M.D., Ph.D., noted in a press release that while doctors use a lot of information to make a diagnosis, “There’s not (now) an efficient or highly accurate way to determine whether the infection is bacterial or viral.”

According to senior researcher, Geoffrey S. Ginsburg, M.D., Ph.D., director of Duke’s Center for Applied Genomics & Precision Medicine, the investigators must analyze an individual’s genetic makeup, 25,000 genes at a time, in order to find the signatures they’re looking for. This wasn’t possible prior to recent technological developments. Even now, measuring a person’s gene expression profile from blood can take as long as 10 hours. The Duke researchers are trying to reduce that to one hour, so that you can be tested and will able to learn whether or not you need an antibiotic while you’re still in your doctor’s office. The test will also help tell whether your symptoms really are due to a cold or flu or might be the result of allergies or other health problems.

In addition, by cutting down on antibiotic use, the test could prevent potentially dangerous allergic reactions to these drugs. A study published in 2008 found that every year, more than 142,000 people, many of them young children, arrive in emergency rooms with serious reactions to an antibiotic. Almost 80 percent of these cases are allergic in nature, ranging from rash to anaphylaxis; the other 20 percent were caused by errors and overdoses. Children under a year old had the highest rate of these problems.

Andrew Weil, M.D.

Source:
Ephraim L. Tsalik et al, “Host gene expression classifiers diagnose acute respiratory illness etiology,” Science Translational Medicine, January 20, 2016, DOI: 10.1126/scitranslmed.aad6873