Rapid influenza testing is associated with reductions in the use of antibiotics in hospitalized adults, according to a report posted online today that will appear in the Feb_26, 2007, print issue of Archives of Internal Medicine, one of the JAMA/Archives journals.
New diagnostic tests are increasing the speed at which influenza and other viral diseases are identified, according to background information in the article. “The rapid diagnosis of influenza in hospital settings is important for infection control and potential antiviral therapy,” the authors write. When used in children with fevers, rapid tests for influenza viruses were shown to reduce the use of antibiotics and other diagnostic tests and shorten hospital stays. However, no similar studies have been done in adults.
Ann R. Falsey, M.D., and colleagues at Rochester General Hospital and University of Rochester School of Medicine and Dentistry, New York, reviewed the medical records of 166 patients with documented influenza hospitalized at their facility during four winters (1999 to 2003). Of these, 86 patients tested positive for influenza on rapid diagnostic testing and 80 either tested negative or did not receive the test.
Fewer patients with positive influenza test results were receiving antibiotics (86 percent or 74 out of 86 patients vs. 99 percent or 79 of 80 patients); 12 (14 percent) of 86 patients with positive results discontinued antibiotics vs. 2 (2 percent) of 80 patients without positive test results. After the researchers controlled for other variables, including underlying heart disease or other conditions, a positive rapid test result was independently associated with withholding or discontinuing antibiotic therapy.
“Although it is encouraging that antibiotic use was reduced in patients whose rapid antigen test result was positive, 61 percent (27/44) of those deemed at low risk for bacterial infection continued to receive antibiotics despite their rapid influenza diagnosis,” the authors write. “Patients who continued to receive antibiotics were more often older, were smokers with higher rates of underlying chronic obstructive pulmonary disease, and had abnormal lung examination results. These trends suggest that physicians were not indiscriminate with their therapy but rather responding to a perceived increased risk of bacterial infection in an older and frailer group.”
No significant differences were found between the two groups in the number of days taking antibiotics, the length of hospital stay or complications arising from antibiotics. Antiviral use was more common among those with positive test results (73 percent, or 63 out of 86 patients) than those with negative or no test results (8 percent, or six out of 80 patients).
Rapid diagnostic tests may affect not only the patient tested, but also lead to broader benefits, such as the reduction of nosocomial (hospital-acquired) influenza. “Given the environment of increasingly severe antibiotic-resistant nosocomial infections, control of inappropriate antibiotic use is highly desirable,” the authors write. “With ever more sophisticated tools ? rapid accurate diagnosis for a wide number of viral pathogens will become available in the near future. To optimize use of these new diagnostic tools and limit antibiotic use in patients with viral infection, more accurate methods of diagnosing concomitant bacterial infections are needed.”