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SATURDAY, June 19 (HealthDayNews) -- One of the most pressing problems in infection care is the overuse of antibiotics, driven in part by doctors who inappropriately prescribe these drugs against viruses instead of the bacteria they're able to destroy.

The misuse of antibiotics isn't intentional, but rather a response to not knowing the source of infections. Often, viruses and bacteria create identical symptoms -- fevers, sore throats, coughing -- without advertising their identity.

Now, scientists say, a simple blood test can help determine which patients require antibiotics and which won't benefit from the drugs. In a recent Swiss study, the test, for a protein called procalcitonin, halved the number of antibiotic prescriptions given to people with lung infections without hurting overall care.

A version of the procalcitonin test is already available in Europe but it has not yet been approved for use in the United States. Administering the test would cost between $30 and $50, although experts say it more than pays for itself by reducing the unnecessary use of antibiotics.

While overuse of antibiotics typically isn't harmful to individual patients, the practice is blamed for the alarming rise in drug-resistant bacteria.

Dr. Stuart Levy, a Tufts University physician and president of the Alliance for the Prudent Use of Antibiotics, said "to have a test like this would in principle be a boon, because if we know that it's viral and not bacterial," doctors could avoid prescribing antibiotics that wouldn't work anyway.

The biggest impact of such a test -- whether for procalcitonin or another infection indicator -- would be in stopping unnecessary antibiotic therapy in the community, where the bulk of misuse occurs, Levy added.

Scott Hanes, a pharmacology researcher at the University of Illinois at Chicago, has studied procalcitonin as a potential test for bacterial infections.

"It looks like it's fairly specific when you have a more systemic infection," Hanes said. "But most literature doesn't support its use in pneumonia because it's fairly localized. The levels [of procalcitonin] never seem to diverge enough from normal to make it" particularly useful in diagnosing the disease.

Even if doctors in the United States were to adopt a procalcitonin test as they have in Europe, Hanes predicted that it would supplement other tools for identifying the causes of infections. These include blood tests for other signals of inflammation, including C-reactive protein, lactate and interleukin (IL)-6, as well as physical exams such as bronchoscopy, in the case of pneumonia.

"It's not going to be relied upon as the sole tool to determine if you're going to receive antibiotics," he said.

More information

The American Academy of Family Physicians has more information about when it's best to use antibiotics and when it isn't.

(SOURCES: Stuart Levy, M.D., president, Alliance for the Prudent Use of Antibiotics; and Scott Hanes, PharmD, clinical associate professor, University of Illinois, Chicago)

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