In a retrospective study, researchers found 86 percent of adult patients who had early testing for the flu were given antibiotics versus 99 percent of patients whose flu was identified later.
"It's very encouraging that physicians can respond to a viral diagnosis," said lead author Dr. Ann Falsey, an associate professor of medicine at the University of Rochester School of Medicine and Dentistry.
"But there's further work to do to help doctors make a decision whether or not their patient really needs antibiotics," she added.
The study, published online Jan. 22 in the Archives of Internal Medicine, is one of the first attempts to research the effects of rapid influenza testing in adults. Previous studies have found rapid testing decreases antibiotic use in feverish children.
The study was funded by the National Institutes of Health; Falsey also serves on the advisory board for Quidel Inc., which markets diagnostic tests.
Falsey and colleagues studied records of 166 patients -- 86 who tested positive for the flu and 80 who tested negative or who did not have a rapid test. Seventy-four of the 86 positive patients took antibiotics, and 79 of the 80 negative or untested patients took antibiotics.
The patients had been admitted to Rochester General Hospital with influenza or respiratory problems during a winter between 1999 and 2003. Hospital policy required influenza testing for all patients with cardiopulmonary diseases admitted between Nov. 15 and April 15.
Rapid flu testing, which has been available for several years, detects viral proteins in the noses of throats of symptomatic patients. Doctors can get results within minutes instead of days, Falsey said.
Many hospitals, particularly large academic centers, already use rapid flu testing as part of their diagnostic tools.
The findings suggest some doctors will not prescribe antibiotics for a viral infection, a positive sign because antibiotics do not attack viruses. However, many influenza viruses will lead to a secondary bacterial infection in patients, so "doctors are not being irrational" in providing antibiotics, Falsey said.
The key is to frame better guidelines and tests for when and for what types of patients antibiotics should be used.
This study was not a randomized trial, so the researchers cannot say for sure the association exists. However, in a statistical analysis Falsey and colleagues found rapid testing was independently associated with lower antibiotic incidence.
Antibiotic resistance has become a mounting problem, as widespread reliance on the medication has created more and more resistant strains of bacteria. Patients may also experience side effects from the drugs, such as rashes, a type of severe diarrhea, and liver and kidney ailments.
That the researchers found a measurable impact at all from rapid testing in a hospital is "very promising," said Dr. Neil Fishman, chairman of the Infectious Diseases Society of America's Antimicrobial Resistance Working Group. That's because many of the patients who are hospitalized with complications of the flu have bacterial pneumonia.
The study's findings could carry the most clout in doctors' offices, Fishman said. Reaching family physicians, who interact with patients every day, could curtail unnecessary antibiotic use on a broader scale, he said.
Physicians often prescribe antibiotics because patients demand them, Fishman said, and testing would "allow the opportunity to actually make a diagnosis and tell the patient this is a viral disease."
In addition, influenza could be avoided entirely by improving prevention strategies, such as vaccinations, said Michael Feldgarden, research director for Reservoirs of Antibiotic Resistance at the Alliance for the Prudent Use of Antibiotics in Boston.
In the United States the medical establishment favors vaccinating the elderly or infirm but not those who are most likely to spread it to others. For instance, vaccinating schoolchildren between ages 5 and 18 may bring down the number of deaths related to influenza, Feldgarden said.
The ultimate question, Feldgarden said, is "what is the best way to use antibiotics responsibly?" As this study showed, rapid diagnosis with "good, old-fashioned" vaccination could be the answer, he said.